# Designing and Building a LED Fixture



## Hoppy

This is getting to be an obsession with me! Hours spent on the computer, searching for parts and data, sketching out design layouts, doing calculations, etc. So, I decided to share what I'm doing, hoping that cooler, more experienced heads will speak up where appropriate.

I have a 45 gallon tank, with about a 30 inch by 15 inch footprint, about 20 inches tall, with a PC light fixture mounted about 24 inches above the substrate level. My goal is to replace the PC guts with a LED array that won't break my bank account wide open, and will give me around 50-100 micromols per sq m per sec of PAR at the substrate level.

One approach is to use relatively low output LED's and many of them to get that intensity. Another is to use the fewest number of LED's that will do the job, but using high output units. The first discovery I made is that lower power LED's don't cost 1/10th of what higher power ones cost, so every arrangement I looked at, using many LED's ended up with a higher material cost than using just 3 high output LED's. So, here is the layout I decided to pursue further:









You can get this LED, http://www.luxeonstar.com/endor-reb...ma-p-179.php?zenid=mq7qbu6j6941aoe1im80dot2b2 with a lens to concentrate the light, for about $24 each.

Next I figured out the approximate angle of the cone of light I would need to get good coverage of the substrate with these. It turns out to be about 45 degrees. (The LED emits light in about a 160 degree cone, but the intensity drops pretty fast as you move from the centerline - the lens will partially correct that.)

To verify that this would give me enough light I found this chart to use to convert the LED lumens output to a PAR intensity at the substrate:







From this it looks like a good number to use is 70 lux per micromol per sq m per sec, where one lux is one lumen per meter squared. Since I will have most of the substrate getting light from 2 LED's I used 25 PAR units to calculate from: 25 x 70 = 1750 lumens per sq. meter. And, the area each LED will primarily illuminate is about a 20 inch diameter circle, or .3 meters squared. 0.3 x 1750 = 525 lumens. The LED I chose gives about 435 lumens output at 700 milliamps of current, but can be driven to 1000 mA, so this comes close to what I want.


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## Hoppy

I realized that some of the spillover light can be caught by reflection off the inside surface of the glass, and by reflecting from the light fixture reflective surfaces. So, I sketched this to see how that might work:









It looks promising, to me, at least. I then priced the heat sink required to keep the LED's cool. That would be a one foot long piece of 5 3/8 wide heat sink, cut along the centerline to make two 2 5/8 wide pieces, placed end to end. A single 120 mm cooling fan mounted above this should keep the heat sink cooled. That adds another $35 for the heat sink and about $20 for the fan.

To power the LED's, drive them, I found a 40 volt DC unit - it takes about 29 volts for the LED's in series and 700+ mAmps of current. This is the unit I found: http://www.cdiweb.com/PortalProductDetail.aspx?ProdId=23479 for about $20. 

So, the total cost of parts would be about $150. So far, so good.


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## epicfish

With my experience with LEDs, you're going to need more than 3 to get an even spread of light at the bottom. If you don't mind sharp shadows and a "spotlight" effect, 3 may be enough.


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## Hoppy

One of the attributes of MH lights is the shimmering effect the surface ripples give you, from the shadowing effect of the small light source. I figure I will get something similar to that effect this way. But, I'm still a bit nervous about whether or not this will be an adequate amount of light, as well as the less than perfect distribution of light.


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## Wasserpest

I don't have personal experience, so take my comments for what they are worth...

I agree with Epic, 3 LEDs will lead to very focused areas of light. I understand the ripple thing, but keep in mind you are comparing 150W HQI bulbs to tiny 3W LED emitters.

When you balance between the output and number of LEDs, lots of low power LEDs are no good, but too few spotlight might not be good either. Rather than 3 triple LEDs, I'd do 9 (or 12) single emitters. When you go from 1 Watt to 3 Watt you can see the brightness triple, but going from 3 Watt to 3x3 Watt doesn't do that.

Check out Cree/Seoul Semiconductor LEDs. LED technology is advancing rapidly, and what was the best yesterday could be replaced by less expensive, more efficient things today.

Adding a lens to a LED to bundle the light sounds weird to me. Add a reflector, sure, but LEDs have a directional light output already, and adding a lens IMO just reduces light output further.

If you add distance between the LEDs and the water surface, keep in mind that the inverse square law darkens things rather quickly.

And finally, for $150 you can build yourself the awesomest, brightest T5 setup you can imagine. But of course that isn't as exciting.

(Just subscribing to your thread).


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## Regloh

Hoppy, 

this might be a subtle effect, but in the schematic in your second post you neglected to take refraction on the water surface into account. 

Refraction happens at the interface of two mediums with different optical indices (sp?). This should slightly reduce the amount of "spill over"

If you are interested in correcting for refraction just search on wikipedia if you don't already know how to do that.


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## merk1_99

My 4 gallon build has cost me about $300. I am going with 12 3 watt Crees. The buckpucks that are running the LEDs will be able to be dimmed. I am going with 12 so they don't give off a spot light effect and will blend well. I think the rule to good blending is 2'' or less between leds, anything more and they spotlight. I know 12 leds is overkill but i will dim them down to a good level of light.


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## Hoppy

Merk, there is no way I would even waste time on this if I felt it would cost me $300 - my wife would kill me! So, while I agree with what you are saying, I'm still looking for a way to get down to around $150.

Regloh, I agree about the refraction, but most of the light will enter the water close enough to vertical for refraction to make little difference, especially given the overall inaccuracy involved with this.

Wasserpest, I agree about the T5's too, but if I go ahead with this, it will be in part to avoid having to buy new bulbs, and it is an opportunity to study up on a new subject for me. As usual, the more I learn the less I find I know! The problem with using more LED's with lower power is that the cost doesn't drop as fast as the power, so I end up again with a $300 fixture. Tonight I started studying the Cree website, and I'm still at the utterly confused stage. A couple of good resources I found were http://www.highend.com/support/training/lightingfaq.asp and http://www.theledlight.com/technical.html A couple more weeks and I may understand the subject a little better.


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## Hoppy

After studying the CREE LED data, and the reference materials I found, it looks like an array of 12 of the 100 lumen CREE LEDs will do what I want, without lenses, with the fixture lowered back down to the top of the tank. Here is the layout:










I think it takes about 4 overlapping LED light cones to get to the 50 micromol PAR that I want, but that is a very crude guesstimate. Twelve LEDs may be overkill, but at about $3.50 each, the price is right. This whole set up should get close to my $150 goal too.


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## Wasserpest

Hoppy said:


> The problem with using more LED's with lower power is that the cost doesn't drop as fast as the power, so I end up again with a $300 fixture.


Nowadays LEDs are available for all sorts of prices. 

http://www.dealextreme.com/details.dx/sku.1445

These guys also have the SSC P7 for $19. Might be good in single bulb config over a 3gal cube. 

Not saying this would be the best in terms of light color and such, just keep looking around and you find things cheaper and cheaper. Same applies to the other parts of the system, like fans, heatsink and such.

Keep in mind that LEDs don't have a very high efficiency - most of the wattage is converted into heat. As you go up in wattage (like 12W for something like the P7) you will have to deal with lotsa heat in a very small spot.

edit - ninja'd big time. Need to type faster. :icon_roll


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## epicfish

Wasserpest said:


> Nowadays LEDs are available for all sorts of prices.
> 
> http://www.dealextreme.com/details.dx/sku.1445
> 
> These guys also have the SSC P7 for $19. Might be good in single bulb config over a 3gal cube.
> 
> Not saying this would be the best in terms of light color and such, just keep looking around and you find things cheaper and cheaper. Same applies to the other parts of the system, like fans, heatsink and such.
> 
> Keep in mind that LEDs don't have a very high efficiency - most of the wattage is converted into heat. As you go up in wattage (like 12W for something like the P7) you will have to deal with lotsa heat in a very small spot.


Actually, I'm using a SSC P7 over an 8" cube. It works beautifully!


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## epicfish

Hoppy said:


> After studying the CREE LED data, and the reference materials I found, it looks like an array of 12 of the 100 lumen CREE LEDs will do what I want, without lenses, with the fixture lowered back down to the top of the tank. Here is the layout:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> I think it takes about 4 overlapping LED light cones to get to the 50 micromol PAR that I want, but that is a very crude guesstimate. Twelve LEDs may be overkill, but at about $3.50 each, the price is right. This whole set up should get close to my $150 goal too.


There we go! I think that setup is much better. Although lower power LEDs aren't proportionally cheaper, the balance between spread, power, and cost in this new array looks pretty good.


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## Hoppy

I suppose it would be reasonably easy to determine what percentage of the output is in the middle 20 degrees of the cone of light, but I didn't even try that. So, I'm not at all sure if this will give the intensity I want. The rest of the cone also emits light, but at a lesser intensity, and that adds to the intensity where it overlaps too. (Just random thoughts as I have been thinking about this.) If nothing else this is an interesting subject to study.


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## Hoppy

Here is what this last setup would cost me: approximately
12 LED's @$3.50 each----------$42 + $10 shipping (guess)
Heat Sink-------------------------$40 + $10 shipping (guess)
48 VDC Power Supply------------$30 + $10 shipping (guess)
Cooling Fan and 12VDC Power---$20 + $10 shipping (guess)
Miscellaneous----------------------$20 (guess)
---------------------Total---------$192 

My current light, running 10 hours a day, is a single 55 watt PC
This LED fixture would use about 33 watts, saving me about 220 watt hours per day, or about 80.3 KW hours per year, at $0.17 per KW hour, saving me $14 per year. My bulb needs replacing about once a year at about $30 each time, with the shipping, for a total annual savings of $44 per year.

My enjoyment from making this is worth??? Priceless? Now, will that sell the wife?


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## PRESTON4479

Hoppy said:


> My enjoyment from making this is worth??? Priceless? Now, will that sell the wife?


That may depend on whether or not that savings of $44 dollars a year is going into her pocket or another DIY project.:icon_wink :hihi:

Let us know if it does convince her so I can start breaking it down like that.


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## Hoppy

PRESTON4479 said:


> That may depend on whether or not that savings of $44 dollars a year is going into her pocket or another DIY project.:icon_wink :hihi:
> 
> Let us know if it does convince her so I can start breaking it down like that.


The trouble is, each time I get the price nailed down, I learn something more, and the price goes up substantially. Now, I'm back to $200+ again, after learning that there is no way I can handle LEDs unless they are preassembled onto "star" mountings, which costs as much as the bare LEDs cost. I don' t recommend selling the wife on a $150 project only to find you are spending $250 on it - I'm not quite ready to sleep out on the deck.


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## Dalban

Hoppy said:


> My bulb needs replacing about once a year at about $30 each time, with the shipping, for a total annual savings of $44 per year.


I'm curious, why do you replace your bulb so often? Typical T5HO bulbs are rated at 20,000-30,000 hours with end-of-life lumen maintenance rated at about 95%.

I'm always keen to find factual, quantitative evidence that backs up the notion that T5 bulbs are significantly dimmer one year into their life. So far I have trouble convincing myself that this isn't a relic of the days when T12 were in vogue.


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## Hoppy

Dalban said:


> I'm curious, why do you replace your bulb so often? Typical T5HO bulbs are rated at 20,000-30,000 hours with end-of-life lumen maintenance rated at about 95%.
> 
> I'm always keen to find factual, quantitative evidence that backs up the notion that T5 bulbs are significantly dimmer one year into their life. So far I have trouble convincing myself that this isn't a relic of the days when T12 were in vogue.


I use GE9325K PC bulbs, not T5. They probably don't require replacing once a year, but I have seen some data that supports a 18 month to 24 month change cycle. I figured on annual replacements to fudge the savings up a bit.


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## Dalban

Hoppy said:


> I figured on annual replacements to *fudge the savings up a bit.*


Ahh. I guess that also explains the high electricity rate you're using (i.e., Alameda PG&E rates are about 25% less the rate you've used). And, for others who are following along, California rates are almost twice as much as many other states.

Fudging the numbers is a great way to fool wives, etc -- but doesn't help advance the hobby. Perhaps we should calculate an honest budget for people who are seriously considering the cost benefit equation.


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## Hoppy

Sacramento uses a multiple tier electricity rate, so, since we are always in the second tier, I used that rate - that number isn't fudged at all. And, I actually have replaced my bulbs in the PC fixture at about one year, because I was disappointed with the bulbs I was using, so I'm not sure that my once a year number was fudged that much. Some folks do it more often. Then there is the intangible "cost benefit" from using less electricity and helping to stop global warming. Plus, as I said, this is a hobby, something to do for fun, and much of the fun I get from the hobby is making new things for my setup, trying them out, and trying to quantify the performance of them. I don't do this as a business.


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## evilc66

Hoppy said:


> The trouble is, each time I get the price nailed down, I learn something more, and the price goes up substantially. Now, I'm back to $200+ again, after learning that there is no way I can handle LEDs unless they are preassembled onto "star" mountings, which costs as much as the bare LEDs cost. I don' t recommend selling the wife on a $150 project only to find you are spending $250 on it - I'm not quite ready to sleep out on the deck.


If you buy the LEDs from ETG or LED Supply, you can get them pre mounted usually for only a dollar more (thats what ETG charges).


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## Hoppy

I just discovered http://www.plantedtank.net/forums/diy/81975-attempting-diy-led-fixture.html today. This is so close to what I wanted to attempt that I am going to wait for the results of malaybiswas's project before attempting my own.


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## evilc66

Didn't get the test done for you this weekend Hoppy. I was fighting with a bum drive on my file server that consumed all my time in between plumbing my reef tank. I'll try and get the numbers for you this week.


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## Hoppy

evilc66 said:


> Didn't get the test done for you this weekend Hoppy. I was fighting with a bum drive on my file server that consumed all my time in between plumbing my reef tank. I'll try and get the numbers for you this week.


I am very slowly learning more about LEDs and how to calculate light "intensity" from them. The more I learn the more I think this really is "rocket science". Some data will be very, very welcome!


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## Hoppy

Will this power supply, http://tinyurl.com/cpk3a8 work to drive two parallel strings of 12 each LEDs with 3.7 volt, 700mA rating? Would this require load resistors in each string to limit the current? 

If it isn't obvious I am looking at a 24 LED array, using these LEDs, http://www.dealextreme.com/details.dx/sku.2395


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## Hoppy

I have the price of this project down to about $150 now, so I am starting to order parts. I plan to use 24 Cree LEDs, ordered here: http://www.dealextreme.com/details.dx/sku.2395 in an array of 3 rows of 8 each, on a grid of about 24 inches by about 6 to 9 inches. Here is how I arrived at this:

I spent a lot of time on http://www.nano-reef.com/forums/index.php?showtopic=188085&st=20 and a couple of others. This particular thread gave me some good data to use to calculate what I would need for my tank and to get the PAR I want. So, I plotted the data on log log paper so I could extrapolate it:









This data is from 11 Cree LED's in an array that is 42.5 square inches, and it would give 240 PAR micromols at the 17 inch distance I will use. I will be illuminating about 450 square inches, so, assuming that the illuminated area that the data is from is the same size as the array, to be conservative, I will need 450/42.5 times that many LEDs, or 116, to get the same PAR. But, I only want about 50 PAR, so I need 50/240 times 116, or 24 LEDs similar to those used in the reference. I chose somewhat less efficient Q2 Cree LEDs for cost savings, and because of the conservative calculation I did above.

More to follow.


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## Hoppy

The layout of the 24 LEDs will be:









This should give me more than 50 PAR in the center of the tank, and pretty close to it around the edges. The yellow circles are the coverage from the center 10 degree half angle of the light - no lenses used. But, the next 10 degrees should theoretically be even higher intensity, due to the focusing effect of the air-water interface.

To power these LEDs I needed to decide how to connect them. If they are all in series, the total voltage required would be about 96 volts, too much for cheap DC converters. So, I decided to split them into two strings of 12 in series, with the strings in parallel. That requires a 48 volt power source with up to 1.4 amps of current. I lucked out because ebay now has just such a DC converter on sale, http://tinyurl.com/cpk3a8 I offered $12 for one, and the offer was accepted. With tax and shipping, that comes to only $23.82, much less than if I were to use "buckpucks", where I would still need a DC supply. But, this also means I need to use current limiting resistors. Here is how I decided what to use:









The two sets of resistors plus the toggle switch lets me toggle between about 700 and 350 mA of current. The numerous resistors are used first to handle the power that has to be dissipated, and because of ebay again! I found these: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:B:EOIBSAA:US:11&Item=180334106900 which are 3 watt 1% 15 ohm resistors, perfect for this use. I plan to put the resistors and switch in a small metal box.


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## Hoppy

Next is the heat sink. Tomorrow I will visit a salvage metals store that is aimed at DIY folks like me. They have a big stock of aluminum extrusions at very low prices. I hope to find 2 or 3 inch channel extrusions, so I can put 8 LEDs on each of three of the channels, then join them, side by side, with aluminum washers separating them for air flow all around each channel. These will give me at least 24 square inches of surface per LED, with enough thickness to also store and easily conduct the heat to the air. At worst, I can buy the channels on ebay, again, for about $30, much less than the cost of a finned heatsink extrusion.









I have spent about $28 so far, not counting the heatsink or LEDs.


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## Hoppy

This morning I visited Blue Collar Supply, with its vast collection of aluminum extrusions. I found they have 8 foot aluminum 3" x 1" x 1/8" thick channel extrusions, for $24.85 each, or $26.78 with tax included. So, now I have spent $55 total. The fun begins!


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## Hoppy

One problem my current limiting scheme was going to give me was if one LED failed open circuit, the increased current through the remaining circuit would possibly desroy those LEDs. So, I redesigned it a bit:










This will let me toggle between 350 mA and 750 mA, and if one LED fails open circuit, the current through the other leg will be limited to less than 1000mA, which shouldn't burn them out.

Today I got the power supply, and it looks very good. And, I got the "heat sink" assembled, but my wife has my camera so I can't get a pic of it yet. I still need to flatten the mounting surfaces a bit and polish it some.

While working on it I decided that "heat sink" isn't the right name for this. It is a heat exchanger, not a heat sink. A heat sink stores heat, but this is supposed to transfer the heat to the air flow going by it. Thinking of it that way makes the design make a lot more sense to me. Spent another $2.24 on nuts and bolts today. Cost is now $30.


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## malaybiswas

Wow! I finally found your thread. I dealextreme link did not work. What Cree LEDs are you using? color? wattage?

BTW...I am getting my LEDs over this weekend. So hopefully I will have my fixtures ready for use by Monday and can help you with some practical data. 

I could not find in your designs, how high you are planning to mount the LEDs, above the tank. Since you have a deep tank(20"), I think you should calculate the lux on the substrate surface based on the distance. I reflector might also be a good idea for restricting light to be wasted outside the tank, unless you have a hood to mount it in.

Anyways, looks good so far. I am subscribed.


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## Hoppy

http://www.dealextreme.com/details.dx/sku.2395 is the LED I plan to use, a Q2 bin, less efficient version of the Cree 3 watt LED. I plan to mount this so it is 17" above the substrate, and I extrapolated the data from the nanoreef thread where the poster actually measured PAR intensity at two depths in the water - heights above the sensor. I'm not yet fully committed to this, but having spent as much as I have I am almost certain to go all the way with it. Any PAR data I can get will be extremely useful.

I won't need any secondary lenses since the distribution is pretty good as it is, at that depth. And, yes, it will be in my existing fixture, which will reflect side light back towards the tank.

This has become an all-consuming obsession for me!


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## Hoppy

I just ordered a couple of fans, http://www.directron.com/sil.html with shipping, they are $25 total, bringing my cost up to $55. If you want to see some testing of fans for noise, check out http://www.directron.com/noise.html. I was shopping for a cheap 12 volt adapter to run the fans when I thought about all of the battery chargers I have collected from cell phones, etc. Great idea! I have a couple that are just the right size and rating. Zero cost for that one.

Today I also got the surface of my "heat sink" sanded and polished as much as I think is needed. I started with 80 grit dry wall sanding paper, which is silicon carbide paper, and it worked very well on aluminum. Then I used 150 and 320 grit to finish sand it. I should have my camera back tonight, so I will plan to take a picture and post it.


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## malaybiswas

Hoppy said:


> I just ordered a couple of fans, http://www.directron.com/sil.html with shipping, they are $25 total, bringing my cost up to $55. If you want to see some testing of fans for noise, check out http://www.directron.com/noise.html. I was shopping for a cheap 12 volt adapter to run the fans when I thought about all of the battery chargers I have collected from cell phones, etc. Great idea! I have a couple that are just the right size and rating. Zero cost for that one.


I got the same fans too but 60mm. 5.99/piece from Fry's and no shipping. For 4 of them for around $26. 2 for each fixture

My drivers can handle the load of the fans too along with the LEDs so I will add them in parallel in the same circuit, so that I don't have to use separate timer for them. And I will have a switch in that leg so that I can switch them off if required without switching off the whole circuit.


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## Hoppy

malaybiswas said:


> I got the same fans too but 60mm. 5.99/piece from Fry's and no shipping. For 4 of them for around $26. 2 for each fixture


Rats!!


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## Hoppy

Here are a couple of pics of the "heat sink". Notice that it is held together with 4 bolts, with short spacers made of 1/8" x 1/2" aluminum bar between the channels to allow for air flow.


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## malaybiswas

nice! If the dimensions match your tanks length & width you have more than sufficient surface area. While I do mine it is good to see a similar idea taking shape in parallel. 

How do you plan to mount it against the reflector?


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## Hoppy

My light fixture is a DIY wooden one, with an 2 x 55 watt AH Supply bright kit in it. So, I will remove all of that, and use stand-offs to screw this to the top of it. The fans will be above that blowing in from the top, each about a quarter of the way from the end of the heatsink.

I'm currently planning to put the current limiting resistors in a small box mounted on the back of the fixture, with the 48 and 12 volt power adapters in the stand mounted on the wall of the stand, and the DC wires twisted together and running up to the light.


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## Hoppy

More parts purchased, at Radio Shack:









A DPDT rocker switch - $4.35 (tax included)
A PC board for resistors - $4.00 (tax included)
Roll of hook-up wire - $7.20 (tax included)

Total cost so far: $70.50, and still no LEDs purchased! Of course I had to buy a little soldering iron and some solder, too, but those don't count, being "tools".


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## Hoppy

I tried to re-learn my soldering skills today, by making the current limiting resistor board. This is definitely a physical skill that needs practice to make it work well, but I think I managed to get all of the resistors soldered in without shorting out any of them.









I have decided to just mount this inside the light fixture against one wall. But, I'm still thinking about how to avoid droplets of moisture from condensation from shorting out the resistors. Some kind of coating seems like the best idea - silicone?

I will have two DC voltage power cables coming in to the light, one 48 volt for the LEDs and one 12 volt for the fans. Managing that neatly was a challenge. But, I found this device in the RadioShack website, so I will use it.









Half will be mounted at the back of the fixture as a socket, and the other half will be the power plug carrying the two voltages from the power converters. These, of course will be spliced to wires from the power converters, and to a 6 foot or so 4 wire cable leading up from under the tank to the fixture.


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## Hoppy

I just ordered 24 Cree 3 watt LEDs from DealExtreme, for $79.46, http://www.dealextreme.com/details.dx/sku.2395 I'm now well past the point of no return on this project.


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## Fish'InMN

A silicone coating would be very messy. I usually spray some clear coat lacquer over any circuit boards that might get condensation/dust/etc. If you need to remove a resistor, just put some nail polish remover on the soldered connections, wipe clean with alcohol, and desolder.

Did this to an LED spotlight over our open-top reef tank, no problems after nearly two years!


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## Hoppy

Fish'InMN said:


> A silicone coating would be very messy. I usually spray some clear coat lacquer over any circuit boards that might get condensation/dust/etc. If you need to remove a resistor, just put some nail polish remover on the soldered connections, wipe clean with alcohol, and desolder.
> 
> Did this to an LED spotlight over our open-top reef tank, no problems after nearly two years!


That seems like a good plan to me. I assume the lacquer is a good enough insulator for that type of use. And, I doubt that there will be much moisture collecting around the board anyway, given how hot LED heatsinks can get.


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## kev82

Hoppy said:


> I just ordered 24 Cree 3 watt LEDs from DealExtreme, for $79.46, http://www.dealextreme.com/details.dx/sku.2395 I'm now well past the point of no return on this project.


Are these 3w? I see no specs there..


I have these on my tank:
http://www.dealextreme.com/details.dx/sku.2394


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## Hoppy

Those are the same LED, but different bin designation - meaning that mine are from the group of that part number which have a lower lumen output, the Q2 bin vs the Q5 bin. Mine will be about 87-94 lumen vs about 107-114 for the Q5, at 350 mA current. As I understand it, a given production run of LEDs will have a wide variation in efficiencies, so they isolate them by the range of outputs, and "bin" them with similiar output ones. There are other differences too, in color temperature, for example, that result in a given LED being in a different bin.

Also, the LED "emitter" can be mounted on a "star" circuit board by different distributers, and I think the ones I'm getting are mounted by DealExtreme.


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## CL

It's lookin' sweet so far. Good luck! That heat sink looks awesome!


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## malaybiswas

Hoppy said:


> More parts purchased, at Radio Shack:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> A DPDT rocker switch - $4.35 (tax included)
> A PC board for resistors - $4.00 (tax included)
> Roll of hook-up wire - $7.20 (tax included)
> 
> Total cost so far: $70.50, and still no LEDs purchased! Of course I had to buy a little soldering iron and some solder, too, but those don't count, being "tools".


Looking good. Just curious about what you are planning with the resistors.


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## Hoppy

malaybiswas said:


> Looking good. Just curious about what you are planning with the resistors.


The resistors became:








This is the current limiting resistor array. The DPDT switch will let me switch from about 350 mA to about 750 mA current. And, the resistor circuit is arranged so if a LED burns out it won't cause a huge current through the parallel LED array.


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## Hoppy

Today I finished the power supply/cable assembly.










On the left, on the end of the cable is the "plug" half of the hard drive extension cable, with two pins carrying 12 volts, and the other two carrying 48 volts, with the green ground wire loose, to be attached to a ground screw on the back of the fixture, to ground the heatsink.

The cable is the only 4 conductor wire I could find, at HD, and it is phone hookup wire, #22 wires. Any thoughts about whether that is enough copper to carry 1.4 amps? (It was cheap!)


----------



## malaybiswas

Since you have separate power supply for LEDs and fan, why are you connecting the wires?

Typically 22 gauge is ok for the fans. For LEDs most manufacturers recommend 18 gauge.


----------



## redman88

Hoppy said:


> Today I finished the power supply/cable assembly.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> On the left, on the end of the cable is the "plug" half of the hard drive extension cable, with two pins carrying 12 volts, and the other two carrying 48 volts, with the green ground wire loose, to be attached to a ground screw on the back of the fixture, to ground the heatsink.
> 
> The cable is the only 4 conductor wire I could find, at HD, and it is phone hookup wire, #22 wires. Any thoughts about whether that is enough copper to carry 1.4 amps? (It was cheap!)


CAT 5 Cable should be able to carry that load.


----------



## Hoppy

malaybiswas said:


> Since you have separate power supply for LEDs and fan, why are you connecting the wires?
> 
> Typically 22 gauge is ok for the fans. For LEDs most manufacturers recommend 18 gauge.


The wires are not interconnected at all. The cable is a 4 wire cable, so I have two wires for each power supply. The 48 volt supply also has a ground wire, which is a straight connection to the ground prong on the 110 VAC plug. I ran that one to the shield wire of the phone cable, in order to have a ground for the heatsink.

CAT 5 cable was one alternative I had, but I didn't find any without plugs on both ends, greatly driving up the cost. If 22 gauge is really too small I will switch it over. I only wasted $2 on the 6 feet of phone cable.

EDIT: I just did some more research: CAT5 cable uses 24 gage wires, which are smaller than the 22 gage wires I now have. Also, I found that the maximum voltage drop I will get on my wires is about 0.8 volts, where 18 gage would give me 0.2 volts drop. I can't see this as significant, so I will leave the cable as is, until testing shows some problem needing a solution.

The only advantage to CAT5 cable is that I could use two pairs of wires for one circuit, and the other two for the other circuit, giving me more current capacity. Since I have a spare Ethernet cable I may salvage it just for that reason - assuming 2 24 gage wires are more copper than 1 22 gage wir.


----------



## malaybiswas

What's up! any progress?


----------



## confuted

Sorry I didn't catch this earlier.

LEDs, as you know, are semiconductors. In normal materials, like metals and carbon, resistance goes up as the temperature increases. Heating losses go as I^2*R, and V=I*R, so at a fixed voltage, as the temperature goes up, the current goes down -- the process is self limiting. Semiconductors, however, work the opposite way - as the temperature goes up, the resistance goes down, causing MORE current to flow, causing it to heat faster ... you get the picture. BOOM. Or melt. Or fizzle. Something along those lines.

That's why you put current limiting resistors in -- which you've done. But you shouldn't connect LEDs in series, since they aren't all identical (they look identical, but manufacturing tolerances say otherwise). Some LEDs will have slightly lower or higher resistance than others, or a different forward voltage, or different temperature coefficients. You can't count on all the LEDs in the chain drawing the same amount of power - especially as they start to heat up. It's entirely possible to have one of your LEDs run away and start a fire.

I'd strongly advise you to connect all of your LEDs in parallel, with a current limiting resistor for each, not in series (or any combination of series and parallel).

Note: Though I am an electrical engineer, I take no responsibility for your project, whether you follow my suggestions or otherwise.


----------



## Hoppy

Progress: Still waiting for DealExtreme to ship my LEDs. Hopefully that will occur tomorrow. And, the more I think and learn about LEDs the less I like my resistor setup for limiting the current. So, I'm scrapping it in favor of a limiter shown in Instructables, which uses a NFET and a NPN transistor to control the current. I can make two limiters, one for each series string of 12 LEDs, for about $5. That sounds like a winner to me.

Confuted, you have it backwards. Parallel LEDs can easily have one LED run away and destroy itself, followed by all of the others. LEDs in series will always all have the same current going through them. Also, put 24 700 mA LEDs in parallel and you need to supply that circuit with 16.8 amps of current, which is a problem with small DC power supplies. It is much easier to provide 48 volts at 700 MA than 3.5 volts at 16.8 amps.


----------



## JimmyYahoo

Hoppy, cant wait to see how this turns out. Been following some LED threads over on the reef forums and had the urge to try this over freshwater. My bank account is happy you beat me to it. Its great to be able to watch the progress and have detailed explanations along the way.

Any thoughts going forward about dimming/automation/color supplementation?


----------



## Hoppy

JimmyYahoo said:


> Hoppy, cant wait to see how this turns out. Been following some LED threads over on the reef forums and had the urge to try this over freshwater. My bank account is happy you beat me to it. Its great to be able to watch the progress and have detailed explanations along the way.
> 
> Any thoughts going forward about dimming/automation/color supplementation?


One man's bank account loss is another man's gain?

I have thought about how to get the great plant and fish color enhancement that GE9325K lights give, perhaps by adding a few red LEDs, but I doubt that I will try it. I have found that my eyes adjust to whatever lighting I use, and eventually the differences caused by the light spectra differences fades away in my perception. As far as dimming goes, I will use a switch to be able to toggle between 350 mA and 700 mA current, but I have no interest at all in "dawn to dusk" style lighting. For now I'm going to be very happy just to get this light to work, and get enough data to be able to predict, with reasonable accuracy, what configuration of LEDs will give a specific PAR value.


----------



## Hoppy

Here is the schematic for the constant current "driver" I plan to try to make today:










These are all tiny parts, with the 4 semiconducter parts costing about $2.50 total, and the resistors costing about $3.00 total. I can probably salvage a piece of the circuit board I used for my ill-fated resistor setup for this device, and use the DPDT switch I already purchased. I'm still thinking about the need for heat sinks for the MOSFETs due to the high current through them. I would just mount them on the LED heat sink, but I suspect that would make the heat sink electrically hot.


----------



## malaybiswas

Hoppy said:


> One man's bank account loss is another man's gain?
> 
> I have thought about how to get the great plant and fish color enhancement that GE9325K lights give, perhaps by adding a few red LEDs, but I doubt that I will try it. I have found that my eyes adjust to whatever lighting I use, and eventually the differences caused by the light spectra differences fades away in my perception. As far as dimming goes, I will use a switch to be able to toggle between 350 mA and 700 mA current, but I have no interest at all in "dawn to dusk" style lighting. For now I'm going to be very happy just to get this light to work, and get enough data to be able to predict, with reasonable accuracy, what configuration of LEDs will give a specific PAR value.


In my experience and opinion red LEDs tend to saturate the color which is more straining to eyes than pleasing (at least to me). I like the combination of blue though.


----------



## Hoppy

malaybiswas said:


> In my experience and opinion red LEDs tend to saturate the color which is more straining to eyes than pleasing (at least to me). I like the combination of blue though.


I noticed in reading other threads on other boards that adding a color can give different effects than you expected. That was why I started with just white ones. Also, it would probably be best to look for a LED that gave a color more like the red-violet of the 9325K bulb, rather than red. Finding that wouldn't be easy.


----------



## malaybiswas

Hoppy said:


> I noticed in reading other threads on other boards that adding a color can give different effects than you expected. That was why I started with just white ones. Also, it would probably be best to look for a LED that gave a color more like the red-violet of the 9325K bulb, rather than red. Finding that wouldn't be easy.


That would take a lot of experiment. Fortunately you may be in luck. I am just hooked enough to this hobby now and want to try new things with LEDs and circuits. I plan to get some more LEDs (colored ones this time) and try out color mixing and auto dimming. No time limits, but may be I can produce some results that can come handy to others.


----------



## Hoppy

Nothing but disappointments today. First, DealExtreme has not shipped my LED order, even though 10 days have passed since I placed the order, and they don't respond to my email asking for the reason for the delay. Then, I wasn't able to locally buy the parts needed for my DIY drivers, so I had to order them on the internet - with the shipping charge greater than the parts cost. 

DealExtreme scares me a bit - the prices are so low I worry about their legitimacy, except others have reported good results with them.


----------



## Cactus Bastard

I've bought about a dozen things from dealextreme in the last year or so, sometimes it does take them a while before parts ship. I've had parts take up to five weeks before they ship out. 
Still can't beat their pricing


----------



## Hoppy

I suppose the slow shipping is the price we pay to get the great sales prices. They do advertise a much faster shipping process than that, but who believes advertising anyway.

I found a little circuit board at Radio Shack that will fit my LED Driver circuit very nicely. It is only 1 7/8 by 2 7/8 inches, with a very usable layout of conductor strips and holes on it. Here is the layout I'm planning on using, unless I find errors in the next couple of days, as I wait for the semiconductor parts I had to order:


----------



## malaybiswas

Hoppy said:


> Nothing but disappointments today. First, DealExtreme has not shipped my LED order, even though 10 days have passed since I placed the order, and they don't respond to my email asking for the reason for the delay. Then, I wasn't able to locally buy the parts needed for my DIY drivers, so I had to order them on the internet - with the shipping charge greater than the parts cost.
> 
> DealExtreme scares me a bit - the prices are so low I worry about their legitimacy, except others have reported good results with them.



None of the online dealers normally stock large quantities of specialty products. If you are buying in bulk they will normally back order. I bought my LEDs directly from Luxeon but still had wait times of 2-4


----------



## kev82

Hoppy said:


> Nothing but disappointments today. First, DealExtreme has not shipped my LED order, even though 10 days have passed since I placed the order, and they don't respond to my email asking for the reason for the delay. Then, I wasn't able to locally buy the parts needed for my DIY drivers, so I had to order them on the internet - with the shipping charge greater than the parts cost.
> 
> DealExtreme scares me a bit - the prices are so low I worry about their legitimacy, except others have reported good results with them.



They are legit. I've ordered probably 10 times in total from them, all sorts of products (flashlights, batteries, rc helicopter, servos, LEDs, digital calipers, toys etc) and everything has been shipped eventually. It usually takes them at least 3 days to ship, but often ~10 days. It took them about 2 weeks when I ordered the crees.


----------



## Hoppy

OK, I'm reassured that my LEDs will arrive eventually. That company is one great resource for LED products, so I suppose I will just have to learn patience. Oooooooom! Oooooom!


----------



## Cactus Bastard

Hoppy said:


> Oooooooom! Oooooom!


Is that your patience noise? 
I think it was my P7s that took over a month to ship, and I was probably making some similar noises during that time, maybe with a bit of gurgling and the occasional squeek :eek5:


----------



## Hoppy

Cactus Bastard said:


> Is that your patience noise?
> I think it was my P7s that took over a month to ship, and I was probably making some similar noises during that time, maybe with a bit of gurgling and the occasional squeek :eek5:


Hey! It worked! My LEDs have been shipped and should arrive in 7-10 working days. Remember the magic chant: "Ooooom oooom...."


----------



## Hoppy

My plans have changed again. The task of switching my light enclosure from an AHS light to the LED light would take me as much as 3 days, and if the LED lights don't work or don't work as well as I hope, I would have to switch back, but the enclosure would by then have too many holes in it, so......I'm going to just make a new enclosure so I can assemble the whole thing at a more leisurely pace, test it, make any needed corrections, etc. before switching the lighting on the tank. This adds only a few dollars to the total cost, and makes the whole project infinitely more workable. I don't see how we can ever have a LED mod kit that is "plug and play".

Right now I am struggling with the assembly of the DIY driver - soldering all of those tiny, tiny connections takes a lot of practice. Electronics assembly is a job for 2 foot tall people with proportionate sized hands and fingers. Hmmmm, I wonder if I can borrow my great granddaughter for a few hours???


----------



## kev82

What driver did you decide to use?


----------



## Hoppy

Hoppy said:


> Here is the schematic for the constant current "driver" I plan to try to make today:


This is the driver circuit I am making, from Instructables.com, but modified a bit to suit my situation.


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## Hoppy

I'm making a wood housing for the LED light now, using a 2' x 4' 3/8 plywood panel from HD. It is 5 ply plywood, so it's a bit better quality than usual, but still just plywood. 










I use a "Skilsaw" to cut most of the parts, using a clamp-on straight edge to guide the saw for a straight cut. And, a power miter saw to cut the 30 degree angles on the end pieces, for accuracy. The plywood is just glued together with "carpenters glue", ordinary yellow glue, which is stronger than any nails or screws anyway. The clamps shown are just there to balance the half assembly to make gluing on the 4th piece easier. Masking tape is an adequate clamping device to hold it until the glue sets up.










This is with the front, back and ends glued together, with small triangular glue blocks in the corners to reinforce the joints so the end grain of the plywood isn't all that holds it together. I have the top glued on too, and have started sanding it all even with a belt sander, but I ripped the belt, so tomorrow I get back to work on it.


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## kev82

Looking good, do you have bigger pics of the joints?


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## malaybiswas

nice job. how are you planning to set this up? hang it over the tank or mount it on the tank?


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## Hoppy

Here is a close-up of one corner joint - just a butt joint.


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## Hoppy

This light will replace this one: http://www.aquaticplantcentral.com/...-cantilevered-light-fixture-4.html#post373878 but I hope to have it suspended a little higher above the tank. Right now the existing fixture is about 6 inches above the tank.


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## Hoppy

The cooling fans going in. By the way, you can't get a cheap 3 inch hole saw. They only seem to come at $20 plus another $15 for a mandrel for it. So, I just used a jig saw to cut the holes.


----------



## evilc66

Psst... Harbor Freight.


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## Hoppy

Harbor Freight is about $5 worth of gas from me! I'm too cheap to try it unless I know I'm going to find what I want. I wish I had thought of it this time though.


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## evilc66

Meh. Live and learn  I guess I'm lucky that I have one close.


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## Hoppy

Small details take a long time! I made some stand-off brackets from sections of the left over aluminum channel, to hold the heat sink in place, and installed the switch which will change the current from 350 to 700 mAmps, plus the socket half of the power line connector.



























The heat sink is just laying on the brackets now, while I decide how to get access to screw it to the brackets. I think I will use clip-on nuts on the brackets, with screws going from the outside of the heat sink into those nuts. But, first I have to find the nuts.


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## redman88

why not drill and tap the brackets


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## Hoppy

redman88 said:


> why not drill and tap the brackets


Yes, that's what I ended up doing. I looked for clip-on nuts, but none that I found could open wide enough for the 1/8" thick aluminum bracket. The brackets are 6061T6 aluminum alloy, which is a very strong, hard aluminum alloy, and they should hold threads very well. Tapping them was harder than usual for aluminum, as a result, but it works well now.

My last two trips to HD ended up with me leaving empty handed, but looking at hardware stimulates my creative juices, so each time I figured out a better way as I searched for what I though I wanted.

Incidentally, I used a combination tap drill thread tap to tap the holes. This is a drill for the first half inch, then becomes a tap for a half inch, followed by a countersink for the last bit. I bought it for another project, so I already had it, and it works extremely well in a cordless drill with speed control.


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## CL

This is really starting to get good!


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## Hoppy

I'm finishing the wood enclosure today and tomorrow, plus probably the next day. It will be oak veneered on the outside and finished with polyurethane. The inside now has two coats of polyurethane, and a strip of aluminum foil glued along the front and back pieces to reflect the stray light down into the tank.

My LEDs left Hong Kong 2 days ago, so given the slowness of aircraft today, I can expect another week before they arrive here.:icon_eek: (I was sure Ford Tri-moters were all out of service now, but....)


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## Hoppy

The oak veneer is now applied, and it is waiting to be finish sanded, stained, and polyurethaned.


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## Cactus Bastard

Wow, that's looking great :thumbsup:


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## Hoppy

Finishing is done. Next will be making the parallelogram cantilever linkage to hold the light over the tank - starting today.


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## Craigthor

Hoppy you have too much free time you need more tanks up and running.  Looks great!


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## Hoppy

My wife keeps asking why I need to keep building light fixtures. My answer is that I am getting at least 3 months of pleasure out of this one, learning about LEDs, how to make them work, figuring out circuits for connecting them and for the drivers, designing the heat sink, designing the enclosure and building it, etc. I consider it cheap entertainment. Oh, and it might be a nice light, too.


----------



## airborne_r6

Hoppy said:


> My wife keeps asking why I need to keep building light fixtures. My answer is that I am getting at least 3 months of pleasure out of this one, learning about LEDs, how to make them work, figuring out circuits for connecting them and for the drivers, designing the heat sink, designing the enclosure and building it, etc. I consider it cheap entertainment. Oh, and it might be a nice light, too.


I dont know about cheap entertainment, my DIY projects usually end up costing more than if I had just bought them. However, I totally agree that I would rather spend 3 months learning how to do something and at the end coming away with a new knowledge set and the product as opposed to just buying it and coming away with just the product. Plus I normally get one or two new tools out of it; "Sorry honey I have to buy it there really isnt another way to do this right."


----------



## Regloh

airborne_r6 said:


> I dont know about cheap entertainment, my DIY projects usually end up costing more than if I had just bought them. However, I totally agree that I would rather spend 3 months learning how to do something and at the end coming away with a new knowledge set and the product as opposed to just buying it and coming away with just the product. Plus I normally get one or two new tools out of it; "Sorry honey I have to buy it there really isnt another way to do this right."


Yeah cheap... i agree..
Do you have any idea what 3 months worth of playing golf cost? 
There are cheaper hobbies, but there are sure as hell more expensive ones ...

Hoppy, I love your new light fixture. I am very close to putting this on my list of things I want to make for my tank


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## Wasserpest

Light it up already... :fish:

That finish looks great. Do you happen to have a link for some info how to apply veneer like that? Or does that take years of sweat and practice? Is the veneer expensive? How do you create clean edges like that?

Okay, back to LEDs...


----------



## macclellan

Hoppy said:


> This is getting to be an obsession with me! Hours spent on the computer, searching for parts and data, sketching out design layouts, doing calculations, etc. So, I decided to share what I'm doing, hoping that cooler, more experienced heads will speak up where appropriate.


Hoppy? Obsessed with DIY gear? Never! 



Hoppy said:


> My current light, running 10 hours a day, is a single 55 watt PC
> This LED fixture would use about 33 watts, saving me about 220 watt hours per day, or about 80.3 KW hours per year, at $0.17 per KW hour, saving me $14 per year. My bulb needs replacing about once a year at about $30 each time, with the shipping, for a total annual savings of $44 per year.


It sure seems like turning off your computer (several hundred watts) and looking at your existing tank with existing light would result in much greater energy conservation, and costs nothing out of pocket. Sorry, just had to say it!


----------



## Hoppy

macclellan said:


> Hoppy? Obsessed with DIY gear? Never!
> 
> 
> 
> It sure seems like turning off your computer (several hundred watts) and looking at your existing tank with existing light would result in much greater energy conservation, and costs nothing out of pocket. Sorry, just had to say it!


Turning off my computer would make me depressed. If I am depressed I might take to visiting one of the local Indian Casinos and seeking pleasure from hitting jackpots. That would likely result in at least a bit more money down the drain than my projects cause. Then, of course, to help with that enjoyment of pulling slot machine levers, I would need liquid refreshment, and would most likely drive home afterwards, possibly causing a 10 car crash on the freeway, with the resultant lawsuits which again might run to more than my DIY projects cost, not to speak of the cost to society for housing and feeding me for a few years in a secure undisclosed location.

Man! I'm good at this. I gotta keep this somewhere to use on the wife.

Back to business:
http://www.woodcraft.com/depts.aspx?deptid=2122 is where I bought my veneer, at their local store here. I just use ordinary contact cement, since I'm not making furniture intended to last for centuries. The nice sharp corners are a result of planing with a miniature block plane, and using sandpaper. But, the real secret, which I rarely divulge is to take my photos from a great enough distance and at the right angle to hide the mistakes.

More business:
I have been stalled on my DIY driver project after discovering that my soldering skills are not going to allow me to use the pre-made circuit boards that look so nice. Last night it finally occurred to me that I have made several DIY printed circuit boards the old fashioned way, with tape, dots, and etchant. That allow one to space things and provide visible spots for solder. So, I have just finished laying out a circuit board design, and am ready to spend a bit more $$ on that - thus saving numerous lives on the freeway.


----------



## Hoppy

Hip hip hurray! Three cheers for Deal Extreme!










Those square markings on the paper cutter this is laying on are 1/2 inch apart. Man, those are LITTLE!


----------



## malaybiswas

Hoppy said:


> Hip hip hurray! Three cheers for Deal Extreme!
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Those square markings on the paper cutter this is laying on are 1/2 inch apart. Man, those are LITTLE!


Cheers!

Those solder pads ARE LITTLE. This star is still managable. IMO, try not to use the Luxeon Rebel stars ever. Those solder pads are half this size. It is a nightmare to solder those.


----------



## CL

YAY! And free shipping too! Did it say "gift" on the package?


----------



## Hoppy

clwatkins10 said:


> YAY! And free shipping too! Did it say "gift" on the package?


I was too busy hugging the package to read what it said.

Smaller solder pads would require me to use a magnifying glass to solder them.


----------



## Dan Knowlton

Hoppy said:


> My wife keeps asking why I need to keep building light fixtures. My answer is that I am getting at least 3 months of pleasure out of this one, learning about LEDs, how to make them work, figuring out circuits for connecting them and for the drivers, designing the heat sink, designing the enclosure and building it, etc. I consider it cheap entertainment. Oh, and it might be a nice light, too.


And point out that she knows where you are - and it is not hanging out in bars.

Dan K.


----------



## Hoppy

Today I bought the stuff to make a printed circuit board for the drivers - prices are a lot higher for this stuff than the last time I did this, back about 30 years ago. And, of course the tape and little dots are smaller, and harder to work with, but I did get it ready for the ferric chloride treatment to remove all of the excess copper.









Tomorrow, I may make a few more of the lines wider. 700 mA seems like a lot of current for such thin lines.

Since I was spending money today, I also bought a tap drill and #4-40 tap to do the holes. I decided that the time spent threading 48 holes would be less than the time spent groping to put nuts on little screws if I didn't tap the holes. I quit totaling the costs now that a lot of it is duplicated as I change my mind, plus for tools and supplies I can use later.


----------



## Wasserpest

Nice! About 30 yrs ago I did the same thing, built a temperature controller on a self-made circuit board like that. Oh the feeling of accomplishment. :tongue:

If you have the space/room/area, increasing the size of the copper conductors seems like a good idea.

Can't wait to see your original and the new fixture shining at a wall, side by side. :biggrin:


----------



## Hoppy

Wasserpest said:


> Nice! About 30 yrs ago I did the same thing, built a temperature controller on a self-made circuit board like that. Oh the feeling of accomplishment. :tongue:


That feeling is pretty close, in space, to the feeling of frustration when it doesn't work - I have experienced both.


> If you have the space/room/area, increasing the size of the copper conductors seems like a good idea.
> 
> Can't wait to see your original and the new fixture shining at a wall, side by side. :biggrin:


Well I did increase some of them, but, of course, after I finished the etching process I wished I had widened them more. Oh well, it's only money.

My new and original fixture will never be side by side, and both operating. I only have one tank and I value my marriage much too much to go for another 45 gallon tank.

Back to business: The etching went easily, but eventually I will have to dispose of the used ferric chloride - nasty stuff.

And, with the added room, more appropriate to my eyesight and hand steadiness, the assembly soldering went like a charm.









Next will be installing this into the fixture housing and wiring it up as far as the leads to the LEDs. Then I will probably go back to mechanical things, since I have now figured out how to make one of my cantilever, parallelogram linkage supports with springs to help with the adjustment, and I want to make that for this fixture. That will mean another $15 for springs.


----------



## CL

That's awesome! You made your own circuit board! Incredible


----------



## Wasserpest

Hoppy said:


> My new and original fixture will never be side by side, and both operating. I only have one tank and I value my marriage much too much to go for another 45 gallon tank.


Never mentioned another tank... shining at a white wall, ya know, that comparison thing? :wink:


----------



## Hoppy

Wasserpest said:


> Never mentioned another tank... shining at a white wall, ya know, that comparison thing? :wink:


OK, that's a good idea. I will try to set that up, but the PAR meter is the real test, and the one I look forward to. I'm trying to get some basic data that will allow us to figure out how much light we will get from a specific arrangement of LEDs at a specific distance from the substrate. But, a good demonstration is always a good idea.


----------



## Hoppy

The circuit board mounted easily in the light fixture housing, and the electrical connections are now made, other than to the LEDs.


----------



## CL

You're almost there!


----------



## Hoppy

Wasserpest's idea about shining the old and new lights on the wall together has made me anxious to get to that point, so I started on mounting the LEDs instead of working on the mounting system for the fixture. I used a acrylic sheet to make a drilling guide to maintain the same spacing for all of the LED mounting holes:










Next will be tapping the holes, and I plan to use my cordless drill to do that. It can have the torque limiter set very low, and will operate very slowly, so it should work. Has anyone tried this?

EDIT: I now have 1/4 of the holes tapped, and the cordless drill makes it much easier than using one of those tap wrenches. With the torque limiter set very low I don't think there is much chance of breaking the tap. But, 36 more holes to go to find out.


----------



## Hoppy

The #4-40 holes are all tapped now, and the cordless drill method for tapping worked very well. When I started a hole I let the drill clutch slip, backed the tap up a bit, let the clutch slip again, backed it up, and next time just tapped straight through. 48 holes went fast, with the only breaks I took being to ease my back from bending over to do this. 

Now the heat sink is installed, the ground wire hooked up, the + and - leads poked up to where they go, and once I get some heat conductive grease I will be ready to install the LEDs.









I suspect the soldering will be a real chore for me, but the solder pads look like they are big enough to make it I Dee ten Tee proof.

EDIT:
An electrical question: Does anyone have an opinion about whether or not the negative lead should also be grounded? The circuit diagram for the driver circuit shows it grounded, but I'm not so sure I think it is desirable to do so.


----------



## CL

This is turning out to be an awesome fixture, Hoppy. I almost took the plunge yesterday and bought some led supplies, because this build is so inspiring. I wound up buying a 70 watt metal halide instead, but I'm also getting some leds to supplement the actinic lighting. Keep up the good work :thumbsup:


----------



## Fish'InMN

I usually tie all my negatives to ground on DC projects, haven't ever had any problems. Makes sense both theoretically and practically; unless you have a project that requires negative voltage, which opens up a whole new can of worms.

Nice work so far!


----------



## malaybiswas

Hoppy said:


> An electrical question: Does anyone have an opinion about whether or not the negative lead should also be grounded? The circuit diagram for the driver circuit shows it grounded, but I'm not so sure I think it is desirable to do so.


Keeping the neg lead grounded will always ensure that your negative potential is 0v. I usually ground all the negatives.


----------



## Hoppy

I will ground the negative leads then.

I now have some of the LEDs installed, using Antec Silver Thermal Compound #5, from Fry's. I'm following the package directions as well as I can.


----------



## Cactus Bastard

Are your LED stars grounded to the base? I've gotten some that were, and others that have been isolated. 

Your tapped holes are awesome btw, super-professional, love it.


----------



## Hoppy

The stars are isolated, with the bases being a white ceramic material. Otherwise I would be up a creek!

I finally got all of the LEDs mounted on the heatsink. The conductive grease I used is easy to apply and the little $10 tube holds a lot more than is needed for 24 LEDs. How well it works is another issue, but I think I read a review of that brand and it was rated as a good substance.










On to soldering, not my favorite pastime, but it has to be done. I plan to tin the wire ends before soldering them on, so it shouldn't be that difficult. (Famous last words?)


----------



## Green Leaf Aquariums

Awesome  This light will be pretty darn bright if its anything like my LED's.

-O


----------



## malaybiswas

Hoppy said:


> The stars are isolated, with the bases being a white ceramic material. Otherwise I would be up a creek!
> 
> I finally got all of the LEDs mounted on the heatsink. The conductive grease I used is easy to apply and the little $10 tube holds a lot more than is needed for 24 LEDs. How well it works is another issue, but I think I read a review of that brand and it was rated as a good substance.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> On to soldering, not my favorite pastime, but it has to be done. I plan to tin the wire ends before soldering them on, so it shouldn't be that difficult. (Famous last words?)


Looking good!! Yes, tinning the wire is highly recommended or else the wires might not get soldered properly. Also from my experience, applying a small coat of solder on the solder pads before attaching the wire makes the job easier.


----------



## Hoppy

malaybiswas said:


> Looking good!! Yes, tinning the wire is highly recommended or else the wires might not get soldered properly. Also from my experience, applying a small coat of solder on the solder pads before attaching the wire makes the job easier.


I thought the solder pads were pre-tinned. They look that way anyway. It isn't really hard to tin them again, but I wish the manufacturer was more clear about that part. Of course, these are not aimed at people like me, more for the real electronic geeks and small business operations.

I admit I'm very nervous about when I will finally push the plug into the wall socket.:eek5: I can just see 24 small columns of smoke!


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## redman88

use the silver solder its tons better for this kind of detail work


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## Hoppy

Silver solder requires a higher temperature to melt, so that would be potentially damaging to the LEDs. It isn't made for electronic work, to the best of my knowledge.


----------



## 691175002

Solder with a small amount of silver (Aka silver bearing solder) tends to melt more easily and can be remelted and worked more.

I normally do smd soldering with silver bearing solder and at one point I ran out and was forced to try a roll of (rather expensive) rohs leadless crap. I ended up ruining a board before giving up.

That being said, almost anything should work fine for wires to pads.


----------



## chonhzilla

This is a very impressive wright-up. Great job.


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## malaybiswas

Hoppy said:


> I thought the solder pads were pre-tinned. They look that way anyway. It isn't really hard to tin them again, but I wish the manufacturer was more clear about that part. Of course, these are not aimed at people like me, more for the real electronic geeks and small business operations.
> 
> I admit I'm very nervous about when I will finally push the plug into the wall socket.:eek5: I can just see 24 small columns of smoke!


they are tinned but they are not uniform or sufficient on each of them. I had problems keeping them soldered and then found a web post that suggested tinning them again. Tried and got good results. 

The biggest reason a led might burn is if the polarity gets reversed by mistake. You can align the anodes and cathodes in a certain direction and solder from one side so that you are following a pattern when soldering. I did it that way and being a beginner did not have any mistakes.

Anyways there definitely won't be 24 columns of smoke. LEDs being diodes will break the circuit the first point any one in series burns saving the rest beyond it. Good luck!


----------



## malaybiswas

Hoppy said:


> Silver solder requires a higher temperature to melt, so that would be potentially damaging to the LEDs. It isn't made for electronic work, to the best of my knowledge.


Silver solder is specifically used for most led reflow soldering and from what I learned on the web it is recommended. I did my second fixture with silver solder. However normal core solder works fine too.


----------



## Hoppy

I understand now: from my ancient history, silver solder is a solder specifically formed to melt at a higher temperature and end up much stronger than lead tin solder and is also referred to as hard solder. Silver soldering was very similar to brazing. The silver solder you are referring to is made for electronic wiring and is intended to avoid using the crappy no-lead solder now sold for soldering wires. I will probably just use the 60-40 solder I have, which does contain lead.

Another question: since the LED stars are now virtually cemented to the heatsink, doesn't that require more soldering pencil wattage to get the temperature up? Seems like the heat sink would keep the solder pad too cool.

And, I'm delighted to hear that I will not get 24 columns of smoke, just one:icon_frow


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## redman88

don't use more then a 15 watt soldering iron near those LED's thats why you need the silver solder


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## Hoppy

I will stop by a RadioShack this morning for their 2% silver solder, which seems to get rave reviews from those who buy it. I notice that Frys sells the same composition solder, but only in much larger quantities, so I assume it is the standard stuff. 

Question: do you tin the wire and solder pad with this solder the same as with tin/lead solder?


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## redman88

it wouldn't hurt.


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## Hoppy

I plan to do the soldering tomorrow. Today I had to baby sit my 4 yr old grandson for 3 hours - roughly equivalent to fighting two bulls at Barcelona. Not a good time for precision soldering.


----------



## evilc66

redman88 said:


> don't use more then a 15 watt soldering iron near those LED's thats why you need the silver solder


?????

Higher wattage irons will allow the area to be soldered to be heated up quicker, preventing the LED from being heated. Especially when mounted to a heatsink, low wattage irons will have a hard getting the solder pad heated up fast enough to melt solder without transferring heat to the LED. Obviously, higher wattage irons will require more skill to use.


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## redman88

i can't remeber where i read that but take a look at the data sheet for the LED for the max temp and dwell time


----------



## Hoppy

evilc66 said:


> ?????
> 
> Higher wattage irons will allow the area to be soldered to be heated up quicker, preventing the LED from being heated. Especially when mounted to a heatsink, low wattage irons will have a hard getting the solder pad heated up fast enough to melt solder without transferring heat to the LED. Obviously, higher wattage irons will require more skill to use.


Intuitively, this makes sense. Did you notice problems getting the solder pads hot enough when the LEDs are mounted on a heatsink? Again, intuitively I expect that it will be much harder with a low wattage soldering iron. All soldering irons reach the same temperature, but high wattage ones do so faster and can maintain that temperature better when lots of heat is being conducted away. Does this mean my 15 watt iron will be a problem? Drat!!


----------



## redman88

the main thing is most led's shouldn't be subjected to high temps for more then 2-3 seconds


----------



## kev82

15w sounds really small.. 40-50w is the number usually being thrown around when people are soldering LED stars.


----------



## Hoppy

Do all soldering irons have grounded tips? And, how important is it to have a grounded tip? I'm finding that there are some big gaps in my knowledge.

Now that I think about it, wouldn't any grounded tip iron have to have a 3 prong, with ground, plug on it?


----------



## Cactus Bastard

Hoppy said:


> Does this mean my 15 watt iron will be a problem? Drat!!


Not necessarily, but you do need to make sure your tip is back up to temp between each connection. 

Once your wires and pads are tinned, soldering stuff this size should be a very rapid process, almost instantaneous. Set the wire against the pad, touch the iron to it, and tap it with the solder. It should immediately flow out into the joint.

Edit - I don't know anything at all about grounded tips? When soldering really sensitive stuff you need to make sure you and your project are both grounded, but I've never had a soldering iron with a ground pin.


----------



## Hoppy

I decided to try my 15 watt iron to see how it works. And, it works fine. The hardest part is tinning the LED pad - you can just sense the heatsink sucking out the heat, but after 3 seconds or so it tins. 









This shows the tiny solder wire used, and the ground connection to the last LEDs in the two parallel chains. A close up:










Only 46 more connections to go!!


----------



## evilc66

redman88 said:


> i can't remeber where i read that but take a look at the data sheet for the LED for the max temp and dwell time


This is an issue with reflow soldering where the entire area is staurated with heat. When dealing with localized heat, like soldering a wire to a pad, you need much higher wattage than 15W. I typically recommend 40W as a starting point. I use an 80W Weller digital soldering station, and that works very nicely, but a little out of the range of most peoples wallets.


----------



## evilc66

Hoppy said:


> I decided to try my 15 watt iron to see how it works. And, it works fine. The hardest part is tinning the LED pad - you can just sense the heatsink sucking out the heat, but after 3 seconds or so it tins.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> This shows the tiny solder wire used, and the ground connection to the last LEDs in the two parallel chains. A close up:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Only 46 more connections to go!!


Biggest issue with low wattage irons is the risk of a cold solder joint. Make sure that the solder has flowed properly and doesn't wrap under itself on the edges, and that the solder is shiny. A flat appearance on the solder is almost always a cold solder joint and it won't stick to the pad.


----------



## Hoppy

All the soldering is done now! Not very difficult at all, even with a 15 watt iron.










That shows it before I plugged it in. I didn't take a photo after plugging it in, because it looked exactly the same.

Now what? I suspect the problem is in the driver circuit I made, but I can't be sure yet. I guess I need to remove the heatsink assembly from the housing and do some testing of the driver circuit. I don't think this can be cold solder joints because neither parallel circult lit up, and I watched to be sure solder flowed on the solder pad and the wire before removing the heat.:icon_frow:help:


----------



## CL

Bummer! I hope you get it figured out


----------



## malaybiswas

If you can get a multimeter it would be really easy to detect the fault in the circuit


----------



## Hoppy

Having a multimeter and understanding how to troubleshoot with it are 2 different things. I have a small basic one, and will be using it for this, but my knowledge of how to do it effectively isn't great. At least I won't get bored for awhile now.


----------



## Wasserpest

You prolly know much more about it than I do, but I would turn it on and measure the voltage on the plus and minus side to make sure it is correctly polarized, and the right level. I don't remember exactly, didn't set it up to deliver 48V or so? Does it? Have you tested the LEDs? I don't want you to blow them up, but you might be able to measure resistance over each of them to make sure there isn't a couple of faulty ones that just "open" and therefore interrupt your circuit.


----------



## Hoppy

I tried powering it up again. This time about half of the LEDs in each series string light up very dimly, with the rest in each string not lighting at all. When I switch to what should be higher (or lower) current, nothing changes about their appearance. Clearly they are running at very low current, too low to light up many of the LEDs. High resistance connection somewhere?:help:


----------



## 691175002

My guess is that your power supply isn't outputting enough voltage. You can test this by temporarily shorting across one or two of the leds in each set. I would wire a multimeter in so that you can watch the current before playing around too much though.

Each LED in series will need 3.7-4V. So if you have 10 in series you will need 37-40V.

The easiest test you can do right now is turn your light on and measure the voltage across the driver while it is hooked up to the LEDs (Just hook in the multimeter in parallel with the string of LEDs). If it is too low you can short across one of the leds temporarily (essentially taking it out of the circuit) and see if it helps.

Assuming the voltage is OK you may have a weak solder joint somewhere (very unlikely) or the powersupply is probably bad. I would place about 80% chance that the voltage is too low.


----------



## Hoppy

I disconnected the 48 volt power supply, measured the voltage and it was 48 volts, possibly 47 volts. I reconnected it and measured from the positive lead at the LEDs to the negative lead, and it was near zero. The first 5 LEDs nearest the positive lead of the 12 in each series glow dimly. None of the others glow at all. I don't see how that can work - the current through all of the LEDs in a series string has to be the same, so they should all glow, or none of them should glow. And, with the same current through each LED they should also split the voltage equally. The last of one of the strings of 5 glowing LEDs isn't anywhere near the last one of the other string - opposite side of the heatsink. And, it is too much of a coincidence that I managed to get lower voltage LEDs all at the positive end of each string. (I know they are not absolutely identical.)

EDIT: I think I see the circuit mistake I made. I grounded the negative leads of the LEDs, but I should have grounded the negative lead from the power supply. I need to find an easy way to correct that.

EDIT: I disconnected the ground from the negative lead entirely, and now all LEDs glow dimly, not changing when I change the switch position which should change the current by a factor of 2. And, the measured voltage across the complete 12 LED series string is near zero. I have to disconnect the power from the LEDs, remove the heatsink from the housing, and only then can I ground the negative power supply lead. What is the chance of that being a fix? zero?


----------



## 691175002

Allright, time for some more measurements. First one is current.








If you connect the multimeter in current mode straight to the driver and then to the LED chain, the current will probably be along the lines of 0.03A (30mA). since they are glowing slightly.

If you are getting a full 0.7A of current then the driver is working properly but the electricity is somehow skipping over the LEDs (probably a short somewhere).









Places to measure voltage.

If the 45 is close to zero then you may have a short or the driver may not be working.

The easiest way to find out is to completely disconnect the driver from the LEDs and measure the voltage across its output with only the multimeter. 








Assuming that your power supply is current limiting it is also safe to short it with only the multimeter and it should read 0.7A (or 0.3A if you set it to that). If you are not getting any power out of the driver, that is the problem.


Depending on which readings match up it should be easy to track down the problem. I'm not an electrical engineer but I am reasonably confident in the numbers.

At this point I would say the problem is likely a short circuit/resistance somewhere that is bypassing the LEDs, but its a hard call since they glow slightly.

If your multimeter has a resistance setting you can try probing around to make sure that things that should be connected are connected and things that shouldn't be connected aren't.


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## Hoppy

Thank you!

I will be away most of the day, so I can't work on this before tomorrow. While checking out my driver circuit I also found I messed up the current setting resistors. If this had worked it would have burned out the LEDs with twice the current they will take! That is called a "silver lining", I guess. I need to correct that before doing any more testing.


----------



## giga

Carefull you don't get a short with those screws hitting the + and - pads with your screws


----------



## Hoppy

giga said:


> Carefull you don't get a short with those screws hitting the + and - pads with your screws


I got the idea for using flathead screws from Kev at http://www.plantedtank.net/forums/diy/85359-6g-nano-led-lighting.html#post822998 The back of the screw is tapered to fit in a countersunk hole, so only the edges of the taper contact the "star". Not even close to shorting them out.

Saturday I spent the day watching my grandchildren play baseball, out in the hot sun for 4 hours, so between that and the allergy problems from the dust, I haven't been back on this project since then. Probably tomorrow, or Wednesday at the latest, I will get back to it.

The fix for my circuit resistor goof isn't too hard, but I need to remove the circuit board to get to it to do it. And, I will add the ground where it belongs, at the same time. Hopefully this will make it work.


----------



## kev82

I don't really know what could be wrong, but my tip would be to start small. Just begin with powering a couple of LEDs and work your way up to the full array.

I noticed you stripped a fair bit more than needed off the wire in the pic giga posted - make sure the exposed wire doesn't touch the heatsink anywhere.

Good luck


----------



## Hoppy

I took the fixture apart, removed the circuit board, and soon discovered another mistake, the one that caused the dim light in the first place. The circuit I'm using to control the current to the LEDs relies on the voltage drop across a low resistance resistor to set the current. I'm using 5 watt, both leads at one end, resistors for this, .75 ohm each. They mount in the circuit board side by side. But, I left a Murphy's Law problem when I laid out the circuit board. It is possible to install the resistors at right angle to how they should be installed, so of course that's what I did. And, that left them shorted out, thus providing nearly zero resistance to the current, and near zero voltage drop to set the circuit current. So, I had near zero current flowing to the LEDs. This could be called a "eye dee ten tee"* mistake.

That's corrected, the other two mistakes corrected, and I'm ready to reassemble the fixture. I expect to see the light before tomorrow is over!

"eye dee ten tee" = ID10T


----------



## evilc66

It's not the arrow, it's the Indian  Don't worry, it happens. I expect to see action shots though.


----------



## Wasserpest

The suspense becomes unbearable. National Guard on standby. :icon_eek:


----------



## Hoppy

Wasserpest said:


> The suspense becomes unbearable. National Guard on standby. :icon_eek:


I will turn off all the smoke alarms first:redface:


----------



## Hoppy

WARNING: Wear welding goggles to view the following photo! 

I got it reassembled this morning and plugged it in. First only 4 LEDs in one string lit up. So, I quickly pulled the plug and rechecked every LED for a ground to the heatsink. No problems found. After lunch I plugged it in again, and all of the LEDs lit up, instantly ionizing all of the air in the garage! OK, maybe it didn't, but WOW, that is some bright light! My guess is it will be way more light than I want, probably more like 200+ micromols than the 50-100 I want. I used my power change switch to try to dim it a bit, but I couldn't see a difference. It looks as painful to see as a HQI light does. After just a few minutes I hear a faint pop and 3 LEDs quit working. That is 3 adjacent ones in a string, but all of the rest continue to work. I'm trying to understand what could cause that.

Anyway, if you all have the welding goggles on, here is the pic I just took:
x
x
x
x
x
x
x
x











If you find yourself blinded, see my lawyer!!


----------



## kev82

Now we're getting somewhere  If the LEDs burned out they were probably fed too much current. Are you sure the drivers are feeding the correct current?


----------



## CL

I knew that that would be incredibly bright!
Get a couple of actinic t5s and set up a reef lol


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## redman88

hmmmm, my next project guess i will take that basic electronics class in the fall and build a light bar for my 29 gallon


----------



## Hoppy

kev82 said:


> Now we're getting somewhere  If the LEDs burned out they were probably fed too much current. Are you sure the drivers are feeding the correct current?


I'm not sure the drivers are feeding the correct current, but they should be, and both parallel strings should have the same current, about 670mA each, or half of that if the switch is in the other position. My multimeter doesn't measure current more than 250mA, so I can't use it for this. At one time I was going to install a little panel mount ammeter, and now I wished I had done so. I may look into doing that now.

If a LED in a string of LEDs wired in series burns out, do the remaining LEDs remain lit? I would expect a burnout to open that circuit. This seems more like a short across LEDs. But, I can't see how that happens if they are all isolated from the heatsink. One effect of a short circuit across 3 LEDs should be overheating and possible failure of a transistor in the driver for that part of the circuit. (Because the FET transistor would have to dissipate more of the 48 volts with 3 missing LED voltage drops.) Unfortunately I can't use the multimeter to measure the voltage drop across each string, with the lights on - it is too blindingly bright to even see the connections.


----------



## kev82

Yeah I think the remaining would stay lit - but they would probably be given the extra current/voltage.

This is pretty much the problem with parallel strings - if a LED dies in either string, the rest of them need to take on the extra electricity. Unless you're using a current mirror.

I'm not an electrician so I'm really bad at explaining this stuff, but basically you want to avoid parallel strings and aim for series if you can. Or go parallel and have a current mirror installed.


----------



## evilc66

Hoppy, repost your circuit and source voltages so we can check it out.


----------



## Hoppy

kev82 said:


> Yeah I think the remaining would stay lit - but they would probably be given the extra current/voltage.
> 
> This is pretty much the problem with parallel strings - if a LED dies in either string, the rest of them need to take on the extra electricity. Unless you're using a current mirror.
> 
> I'm not an electrician so I'm really bad at explaining this stuff, but basically you want to avoid parallel strings and aim for series if you can. Or go parallel and have a current mirror installed.


A crude schematic of how I have the LEDs hooked up is:









There are two strings of 12 LEDs in series, each with its own driver, with the two strings in parallel. This was necessary to fit the 48 volt power supply I have. A failure in one of the strings will not affect the other string. And, logic tells me if one of a group of things wired in series fails, the others lose their power too, since the same current flows through all of them. If one LED fails so that it has zero voltage drop, the only effect of that is to make the driver dissipate the extra voltage, as heat. But, I don't know if LEDs fail so that they have zero voltage drop. In any case the current flowing through that series string will remain the same, controlled by the driver.

I guess the question is: do LEDs fail so the voltage drop across them goes to zero or near zero, as the current continues through them, with zero or near zero electrical resistance? I will google and see if I can find the answer, but if anyone knows, please tell me.


----------



## malaybiswas

if a LED fails, both current and voltage drop across it is 0.

did you find out what the "pop" was? Are the solders intact for the 3 LEDs? Remember that the LEDs will heat up pretty fast, so if there is any weak solder, that can pop out.


----------



## Regloh

I think you may have created a short across those LED's. The fact that they are right in sequence may be just coincidence. This does mean that the remaining LEDs in that line are taking a higher voltage, so be careful.


----------



## Hoppy

Regloh said:


> I think you may have created a short across those LED's. The fact that they are right in sequence may be just coincidence. This does mean that the remaining LEDs in that line are taking a higher voltage, so be careful.


It doesn't change the voltage seen by the other LEDs, since they all run at the voltage they choose. All you can change is the current going through them. But, the driver does have to get rid of the excess voltage, so it can cause a failure of the driver.

I think it is a short too, but multimeter readings of resistance don't show any short. Unfortunately, when the light is on, the glare is so intense I can't see to use the multimeter to measure the voltage drop on the three that are not lit. I might be able to somehow attach the probes to the LED's then turn on the light, but my cheap little multimeter doesn't have alligator clips for that.

I read through the Wikipedia article about LEDs and there are a very few failure modes that short out the LED. But, it looks like they would then show a short when checked with an ohmmeter, with the power off, and they don't.


----------



## Hoppy

malaybiswas said:


> if a LED fails, both current and voltage drop across it is 0.
> 
> did you find out what the "pop" was? Are the solders intact for the 3 LEDs? Remember that the LEDs will heat up pretty fast, so if there is any weak solder, that can pop out.


I can't find any soldering problem with those 3 LEDs, and if I did, wouldn't that result in an open circuit, so none of the LEDs in that series would light up? And, so far I can't find anything that would have caused the "pop", which wasn't at all loud.

I'm still thinking about what the best way to trouble shoot this is - given that all I can get to is the LED side of the heat sink, without disconnecting the power leads to the LEDs.


----------



## Wasserpest

Is there a simple way to verify that they actually "popped"? Not sure what their normal voltage is, about 2 or 3V? Can you connect a power source (1.5v battery, or 2?) to them and see if they still light or are truly fubar? If they are dead, you'll probably have to redo things, right? Somehow reduce the current?


----------



## 691175002

LEDs can fail both open and closed, frankly failing closed is better since that way the entire string wont die.

Don't worry about the driver, assuming it is a switching type it should not be dissipating much heat to begin with. Most electronics are rated to 70C or more anyways. If you can touch it without getting burns its fine (I wouldn't touch 48V while its on though).

I'm thinking short as well, mainly because the chances of three sequential LEDs all dying at the same time but not taking out any other ones in the string is near zero.


----------



## Regloh

Actually, are the three dead ones at the end of a string? If that is the case you are looking for one little short circuit around the first one. I think you had mentioned that you grounded the negatives to the heat sink? That could explain it. That short would be cutting the 3 LED's out of the circuit. This may be really good news, as the LED's may still be viable... if I'm right.


----------



## Hoppy

Regloh said:


> Actually, are the three dead ones at the end of a string? If that is the case you are looking for one little short circuit around the first one. I think you had mentioned that you grounded the negatives to the heat sink? That could explain it. That short would be cutting the 3 LED's out of the circuit. This may be really good news, as the LED's may still be viable... if I'm right.


The three dead ones are the first 3 at the + end of the string, where the + lead connects. This means those have the highest voltage above ground on them, which argues for a short to ground, because the heat sink is grounded. The negative or, more accurately, the zero voltage end of the string isn't at ground potential, but is above ground, since the current then flows through the switching transistor in the driver, and through about a .75 or 1.5 ohm resistor. It would help a lot if I measured the voltage drop across the 3 dead ones, with the power on. If it is much less than 9 to 12 volts, the LEDs are shorted internally. (I think.) But, I need to solder leads to the multimeter probes and to the LED pads to do that.


----------



## Regloh

Eh... you just need to grow a third hand


----------



## Hoppy

Regloh said:


> Eh... you just need to grow a third hand


Will regular solder work for attaching my third hand:icon_eek:


----------



## airborne_r6

Hoppy said:


> Will regular solder work for attaching my third hand:icon_eek:


As long as it is lead free to avoid long term health problems it should be just fine.


----------



## Hoppy

I have a new clue! A few minutes ago I went out to see if I could get a quick PAR reading of the intensity, in the garage, in the air. I plugged it in, it flashed on, then off. Now, both series strings are totally off. It looks to me like they were running at too high a current, and, since my 48 volt supply is a 1.45 amp supply, I probably exceeded that and it shut down - or failed. This because both strings failed simultaneously, and there isn't any other spot I can think of where a single failure shuts the whole thing off.

This is beginning to annoy me. (But, just beginning.)


----------



## kev82

Don't lose faith just yet - Pioneers are bound to run into troubles


----------



## CardBoardBoxProcessor

so what exactly is needed? a DC converter.. then some resistor? and then just string them all together?


----------



## Hoppy

CardBoardBoxProcessor said:


> so what exactly is needed? a DC converter.. then some resistor? and then just string them all together?


What is needed is:
A DC supply with a voltage just a little above the voltage drop across each LED times the number you have in series.
A LED driver which is an electronic device that holds a constant electric current through it so it powers that group of series connected LEDs at a constant current even when the voltage drop across them changes, as it does. That current, for Cree LEDs has to be 350 mA for the longest life, but not the maximum light output, 700 mA for the best combination of life and light output, or 1000 mA to get the maximum light output, but with reduced LED life.
A heatsink, to dissipate the heat generated by the junction of the LED, which would otherwise cause a quick failure of the LED.
A fan or fans, to cool the heatsink, and, if needed, a 12 VDC supply for the fan or fans.
Finally, a fat bank account or the ingenuity to build your own driver circuits and make your own heatsink.

The primary skills needed are the ability to solder very small connections quickly so you don't overheat the LED while soldering the wires to it, and enough mechanical skill to mount all of those LEDs on the heatsink, and assemble all of the electric parts into a fixture.


----------



## Hoppy

I'm ready to get my Master Electrician badge now! After lots of careful study, calculations, research into the basic theory behind LEDs, I was able to solve my latest problem - the all-dead LED problem. Just to test all of you, when you turn on an electrical device and it don't work, what is the primary probable cause? Think carefully - this is a trick question.

Do you give up? Well, today needed to work on something else in the garage, so I had to move the LED fixture out of the way first. So I picked up the "power Bricks", the DC supplies, and started to look for a good place to keep them, when I saw a short electrical cord laying on the floor. My Master Electrician skills then came into play. I went over my mental check list of short electrical cords, and checked off all of the possibilities - of which there was one. That is the cord that connects the 48 volt DC supply to the extension cord. Yep, it fell out.

So, it was time to test my analytical skills. I plugged it back in, plugged it into the extension cord, said "let there be light" and was immediately blinded again!:redface::redface::redface:

To avoid another of these complex electrical problems that seem to dog me, I ran and got the PAR meter - ok, I don't do much running now, but I got it in any case - and took some measurements. Another triumph for the Master Electrician. At about 20 inches from the light I got 50-70 micromols, just as I was shooting for!:thumbsup:

The light is pretty uniform, hitting 70 only at what appears to be directly above a LED, but it could just be my unsteady hand trying to hold a constant distance as I moved the sensor around. In any case my design does give about what I wanted, at the height I wanted it, in air. With water in the picture I suspect the intensity will be a little more, due to the focusing effect of the air to water interface. I feel good again!roud::icon_bigg


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## CL

That's good to hear, Hoppy. lol, it was unplugged :hihi:


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## Hoppy

I started work on the linkage to support the fixture above the tank today. It should only take a couple of days to make that. Once that part is completed and installed on the fixture, I can replace my AHS light fixture and get some in-tank measurements of PAR. But, to do that I need to redo the aquascaping in the tank to get room to make the measurements. That isn't a problem, since I'm ready to do that anyway.


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## sunfire99

Any updates Hoppy?


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## Hoppy

Here is how it stands right this minute:










Tomorrow I plan to visit a local Grainger store for springs to assist it holding up the 8 pound weight of the fixture. Then, assuming that works out as my calculations say it will, I will clean up and heavily prune my tank, first because it badly needs it, and second, so I can get some PAR measurements that mean something. 

There is a light at the end of the tunnel!


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## CL

Hoppy said:


> Here is how it stands right this minute:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Tomorrow I plan to visit a local Grainger store for springs to assist it holding up the 8 pound weight of the fixture. Then, assuming that works out as my calculations say it will, I will clean up and heavily prune my tank, first because it badly needs it, and second, so I can get some PAR measurements that mean something.
> 
> There is a light at the end of the tunnel!


I'm glad to see the hinge system again! It's also good to see that oyu are using the spring idea 
Great DIY!


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## eyebeatbadgers

Very informative thread Hoppy, well done. How close (or not close) did you get to your budget?


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## Hoppy

eyebeatbadgers said:


> Very informative thread Hoppy, well done. How close (or not close) did you get to your budget?


Look!! Over there!! Isn't that Elvis Presley?

OK, no, it isn't Elvis.

Well, I was shooting for $150 budget, but I made enough mistakes and false starts, especially on the constant current device, that I ran over that. The last I figured it out, I was at around $170 for just the light fixture part, not the hood. With the hood it looks like it will be closer to $200-$225. Every time I did something it took a trip to HD to buy nickel and dime stuff, which today costs $5-$10. Yesterday I bought 3 little packages of screws, washers, and nuts, and it came to almost $5. I needed some adhesive to laminate two strips of 1/8" x 3/4" aluminum together, and that came to about $5. Do things like that enough times and you are spending real money. But a major addition was buying stuff for the printed circuit board. Because I used a local electronic hobby supply place, forgetting about Frys, those parts ended up costing about $20. Part of DIY is SIY (spend it yourself).

As I keep telling my wife, I have had about 2 months of solid, great entertainment from this project, and will enjoy it for many more months, all for around $200. If we decide to take in the Sacramento Jazz Festival this weekend it will cost us about $100 just for one day of enjoyment. So, it has to be viewed in perspective. (I have a degree in rationalizing, and that helps too!)


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## airborne_r6

Did you ever solve the problem of the 3 LEDs that were apparently burned out?


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## Hoppy

airborne_r6 said:


> Did you ever solve the problem of the 3 LEDs that were apparently burned out?


No, those three still don't light up. I have been thinking about it, and the only things I can think of are to buy 3 more, or to solder wire to my multimeter probes, and then to the solder pads on the LEDs to see what the voltage drop across them is. But, once I found that I have plenty of light without them, I have not had an incentive to do much about them.

One option I just thought of is to have my wife plug the light in as I hold the probes on the solder pads, and keep my eyes averted so I'm not blinded as I watch the multimeter reading. I may actually try that.


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## Minsc

Really dark sunglasses, perhaps?

I'm looking forward to the PAR comparisons!


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## Hoppy

I finally got the balancing springs attached. It works, but those springs really have a load on them. It took two bloody knuckles to get the aluminum end pieces on the springs, too. This might be too dangerous to have suspended at eye level over the tank - if a spring breaks, a piece could be ejected into someone's face. I need to think about this some more, but, in any case, the light fixture is ready to install now. (After I do some heavy pruning and cleaning of the tank.)


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## Regloh

Very nice work! I like it.
It looks like you have access to a machine shop or something similar 

I wouldn't be too concerned with the springs as those are extension springs. They should only collapse to one side if they break at one end. You could try "hiding" them inside a tube shaped housing of sorts, but that becomes impossible to assemble. 
I would leave it the way it is. I had a desk lamp once that looked very similar. 

I am looking forward to the light readings as well...


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## Hoppy

Regloh said:


> Very nice work! I like it.
> It looks like you have access to a machine shop or something similar
> 
> I wouldn't be too concerned with the springs as those are extension springs. They should only collapse to one side if they break at one end. You could try "hiding" them inside a tube shaped housing of sorts, but that becomes impossible to assemble.
> I would leave it the way it is. I had a desk lamp once that looked very similar.
> 
> I am looking forward to the light readings as well...


My "machine shop" is a hacksaw, two files, some silicon carbide paper, and a couple of hand drills. Aluminum isn't at all hard to work with, even when hardened to T6 as this stuff is. It seems "gummy" when you hacksaw it, and I found that my power "demolition" saw is much harder to use on it than a simple old hacksaw. It also polishes very nicely with silicon carbide papers.

I'm getting over my fear of those springs. The struggle to get the aluminum extensions on got to me for awhile. (Man should have evolved with three arms, not two.)


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## Hoppy

Today is the big day - triumph plus some problems!

First, I installed the light fixture, found the clamping knobs won't hold the weight of the fixture well enough, so I added some wood blocks to fix the position where I wanted it.










The tank is sparsely planted because I removed most of the plants to get room to make the measurements.

I spent another $12 on a 3 outlet, grounded extension cord so one timer will turn on both the 12 VDC and 48 VDC supplies. My cabinet is so crowded with stuff I had to put the power supplies outside the cabinet between it and the wall. But, then I plugged it in and it worked! The 48 VDC supply was getting pretty warm, so I quickly took PAR readings and plotted my data.










As you can see, my AH Supply light has weakened a bit since I last measured its PAR. It now gives me about 30 - 40 micromols at the substrate. But, the LED fixture gives about 65 micromols at the same location - about twice as much light with less wattage - about 32 watts vs about 55 watts. It also gives very uniform light throughout the tank, with the PAR rising to about 100 half way to the water surface vs. about 50 with the AHS light, and about 150 at the water surface vs about 95 for the AHS light. There is some light decrease as the sensor is moved front to back and left to right in the tank, about a 50% drop, maximum, at the glass-front, where it is not directly under any LEDs, due to the curvature of the front glass - and no drop at all at the back. Left to right the drop is only about 33% at one end, but considerably more at the other, probably because of my problem holding the sensor straight up and down at that location.

Now the problems: the switch I installed to cut the LED current in half isn't working at all, based on PAR readings. That is fixable. Then the light shut itself off after about 30 minutes, obviously when the 48 volt power supply got too warm. That suggest that the 1.45 amp limit for that supply was exceeded. That too is fixable, by reducing the current setting, which will also reduce the PAR to closer to what I want.


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## evilc66

So close. Glad to see you are making progress. How are you liking the color temp of the LEDs?


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## Hoppy

The color temperature is a very nice crisp white, which doesn't emphasize the reds like my GE9325K light does, but it is going to be easy for my eyes to adapt to. I didn't mention the "shimmer", but that is spectacular! Because I keep pretty heavy surface rippling on my tank, the whole substrate is literally alive with moving lights. Frankly it was distressing to see at first - almost mesmerizing - but I think I will quickly get used to it too. I had no idea that I would get that much of an effect. And, you can see the bright points on the substrate corresponding to the locations of the LEDs, but they are subtle, and largely obscured by the shimmer.

The one goal I did achieve is that now I think I will be able to predict what the intensity will be from an array of these LEDs spaced 3 inches apart, for almost any distance from the lights to the substrate.

But, the major problem remains: the unit is now dead, probably with the 48 volt power supply cooked. More $$$ will fix that, but now I'm not at all sure that DIYing the power/current limiters will be a good move. I still need to study this some more. Having to buy the drivers and good power supplies will push the cost for a light like this far above what I hoped to achieve.

For now, I will reinstall my old light fixture, probably using my newer version of the parallelogram linkage on it.


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## sunfire99

Hoppy, Did you consider using a premanufactured supply like this that uses switching supply technology and is current limiting, and fairly cheap? Lower voltage would require that you use more parallel strings of LED's but are generally cheaper even in the higher amperage models than units that use higher voltages. That's just one link, but I'm sure there are many places to choose from. Was the supply you were using a switching supply? If not look at switching power supplies, or even better a pulse width modulator specifically. Many supplies called "switching" use PWM technology but there are many ways to design a switching supply. They all use feedback oscillators to regulate their output and "switch" several times a second to maintain their output. PWM's are common in things like flat screen tv's, are very small, run cool and energy efficient.


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## Hoppy

Yes, I did look carefully at power supplies like you linked to. That one you linked to costs $50, is made by Mean Well, where I had found one that would do exactly what I need, but would have eaten up far too much of my $150 budget goal. So, that led me to look at making my own drivers, and using a cheap 48 volt DC supply.

Today, I replaced the old AHS light on the tank, and did some testing of the 48 volt supply I used. As I expected, it is dead, and it is a sealed unit that can't be repaired. So, it's back to the drawing board.

I also want to reduce the LED current to about 500 mA to get closer to the light intensity I want, which led me to look back at the other alternatives for DIY drivers. One, using an IC voltage regulator looks perfect. I read up on those devices, so I can see how the circuit works, read the manufacturers literature, including design hints, and came up with this:









It appears from all I can find, and my understanding of the circuit, that this will work very well. If one of the two parallel strings of LEDs fails shorted out, the maximum current will go only to 1000 mA to the other string, which is within the limit for those LEDs. This will use only 3 components (one consisting of some parallel resistors) and should be a lot easier to assemble than my 2 transistor circuit was. If anyone sees a flaw in this design, please speak up

Meanwhile, I plan to visit the surplus electronics store near me to see if I can find a better 48 volt supply. I know it will be dirt cheap if I can find one there.


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## Wasserpest

I have a beginners question, hopefully not too much OT...

Why are we so much after the current limiting packs and bucks and bricks?

If you apply the correct voltage to a LED, it should light up, right? Say you have LEDs that run at their best at 2.5V. Why can't we take something cheap, like a computer PSU, and use the 5V rail and run say 2 LEDs in series (to get the 2.5V) and then put 12 or however many of them in parallel?


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## 691175002

The LM317 is a linear regulator and has a dropout of 3V which is on the high side. Since it is a linear regulator instead of switching on and off like a transistor it dissipates any excess voltage as heat and therefore can get insanely hot.

I prefer the many clones of the LM317 with lower dropouts (1V). You can even pick them up as free samples. I already had a bunch of them so I went with the linear regulator design; however, if I were to buy the parts I would go with the transistor design since it is more efficient and runs cooler.


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## Hoppy

Wasserpest said:


> I have a beginners question, hopefully not too much OT...
> 
> Why are we so much after the current limiting packs and bucks and bricks?
> 
> If you apply the correct voltage to a LED, it should light up, right? Say you have LEDs that run at their best at 2.5V. Why can't we take something cheap, like a computer PSU, and use the 5V rail and run say 2 LEDs in series (to get the 2.5V) and then put 12 or however many of them in parallel?


The reason that doesn't work is because as the current increases the voltage drop across the LED goes down, which causes the current to go up some more, dropping the voltage more, etc. It is an unstable circuit, which will burn up the LED. If you use a cheap battery to power a LED, it works, because as the current goes up the battery internal resistance reduces the voltage available, thus countering the rising LED current. It is a stable circuit.

The constant current driver circuits, drop the applied voltage to keep the current steady through the LED at whatever the circuit design allows.



691175002 said:


> The LM317 is a linear regulator and has a dropout of 3V which is on the high side. Since it is a linear regulator instead of switching on and off like a transistor it dissipates any excess voltage as heat and therefore can get insanely hot.
> 
> I prefer the many clones of the LM317 with lower dropouts (1V). You can even pick them up as free samples. I already had a bunch of them so I went with the linear regulator design; however, if I were to buy the parts I would go with the transistor design since it is more efficient and runs cooler.


That is a good point, and I will do some more research based on that. The voltage limiter does allow attaching a small heat sink, which I was thinking of doing. I'm also wondering about a voltage dropping resistor in series with the Power In line, which could work given that I plan to only use one fixed current. It still wastes power, but doesn't overheat the voltage regulator.


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## 691175002

Hoppy said:


> That is a good point, and I will do some more research based on that. The voltage limiter does allow attaching a small heat sink, which I was thinking of doing. I'm also wondering about a voltage dropping resistor in series with the Power In line, which could work given that I plan to only use one fixed current. It still wastes power, but doesn't overheat the voltage regulator.


I love the regulator circuit since it is so simple but it can seriously put out an incredible amount of heat. This circuit is dropping 6V at 0.7A and it gets the entire bar of black anodized aluminum hot to the touch. 










I've used the little heatsinks that screw onto the TO-220 packages and honestly I doubt they are up for the job. I will be bolting the regulators onto an aluminum bar.

I'm not an electrical engineer, but the math I do know tells me that to keep it under 100C you will need (100-30)/4 or ~17W/C worth of heatsinking. 17W/C means that for every watt of power dissipated, the heatsink will be 17C above room temperature. The lower the W/C rating the better.

For comparison, this TO-220 heatsink is only 36W/C.
http://uk.farnell.com/fischer-elektronik/sk-95-25sa-220/heat-sink-to-220-36-c-w/dp/4621554
This guy would be running at nearly 180C (350f) after a few hours.

There are some which are significantly better though, just make sure you know what you are buying:
http://uk.farnell.com/aavid-thermalloy/6100bg/heat-sink-to-220-202-9-c-w/dp/1213466

On the plus side, regulator ICs have built in thermal protection so destroying one would take an incredible amount of effort.


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## sunfire99

It might take some messing with to find the right value, but you could also use a resistor shunt in parallel with the regulator. That would decrease the heat generated by the regulator. That's a fairly common practice with these linear regulators. Of course the resistor would generate heat as well, but use a nice oversized wattage resistor that's made to run that hot.


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## Hoppy

691175002 said:


> I love the regulator circuit since it is so simple but it can seriously put out an incredible amount of heat. This circuit is dropping 6V at 0.7A and it gets the entire bar of black anodized aluminum hot to the touch.
> 
> I've used the little heatsinks that screw onto the TO-220 packages and honestly I doubt they are up for the job. I will be bolting the regulators onto an aluminum bar.
> 
> I'm not an electrical engineer, but the math I do know tells me that to keep it under 100C you will need (100-30)/4 or ~17W/C worth of heatsinking. 17W/C means that for every watt of power dissipated, the heatsink will be 17C above room temperature. The lower the W/C rating the better.
> 
> For comparison, this TO-220 heatsink is only 36W/C.
> http://uk.farnell.com/fischer-elektronik/sk-95-25sa-220/heat-sink-to-220-36-c-w/dp/4621554
> This guy would be running at nearly 180C (350f) after a few hours.
> 
> There are some which are significantly better though, just make sure you know what you are buying:
> http://uk.farnell.com/aavid-thermalloy/6100bg/heat-sink-to-220-202-9-c-w/dp/1213466
> 
> On the plus side, regulator ICs have built in thermal protection so destroying one would take an incredible amount of effort.


Wow! That is a bit scary. I think I will put 2 ohms of resistors in series with the incoming 48 VDC, since the voltage across each LED will be about 3.5 volts at the 625 mA I expect to be running at. That means I need about 42 volts for the 12 LEDs in series, plus another 3 volts to make the regulator operate, or only 45 volts total. Putting 2 ohms in series will drop about 2.75 volts of that (2X current, with two strings in parallel.) This leaves the regulator dissipating only 3.25 volts, or about 4 watts of power. This is about the same as your illustrated test had. Then I can attach an aluminum bar to the regulator, with thermal grease between them, and hopefully keep the temperature below the 125C limit for the junctions. I hadn't planned on that, thinking that device could handle the heat with its built in heat sink. On the plus side, this will be mounted in the area where the LED cooling fans are creating a breeze.

Now, to find a good enough 48 volt DC supply.:confused1:


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## Hoppy

sunfire99 said:


> It might take some messing with to find the right value, but you could also use a resistor shunt in parallel with the regulator. That would decrease the heat generated by the regulator. That's a fairly common practice with these linear regulators. Of course the resistor would generate heat as well, but use a nice oversized wattage resistor that's made to run that hot.


Are you saying let the current regulator circuit control some fraction of the current I want, with the remaining fraction being controlled by a load resistor? Say, reduce the current through the regulator from 1.25 amps to say .85 amps, thus reducing the power dissipated by the regulator almost in half? Then add a bypass through a resistor sized to provide the remaining .40 amps? That looks tricky. I will have to play with that for awhile.

EDIT: Ok, how does this look? This should cut the power loss through the voltage regulator by more than half, which may allow using only the built in heat sink, or at least only a small aluminum bar heat sink.


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## sunfire99

Hoppy said:


> Are you saying let the current regulator circuit control some fraction of the current I want, with the remaining fraction being controlled by a load resistor? Say, reduce the current through the regulator from 1.25 amps to say .85 amps, thus reducing the power dissipated by the regulator almost in half? Then add a bypass through a resistor sized to provide the remaining .40 amps? That looks tricky. I will have to play with that for awhile.
> 
> EDIT: Ok, how does this look? This should cut the power loss through the voltage regulator by more than half, which may allow using only the built in heat sink, or at least only a small aluminum bar heat sink.


Yes, that looks like what I suggested. The resistor value should be high enough to not allow full LED function, but still low enough to shunt some of the current. The actual value of the resistor is hard to figure exactly with the regulator carrying "x" percentage of the load, but your schematic looks very close. You'll probably need a 2-3 watt resistor, but I'd put a 5 or even 10 watt sand resistor in there. They seem to tolerate long term heating better than traditional wirewounds. I would agree that you'd then get by with a small bar heatsink or one of these or similar.


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## Hoppy

I keep rethinking this circuit - it's enough to make ones head explode! Now, here is how I see this circuit working:
First, the 25 ohm resistor drops the 48 volt power down to the voltage the LEDs run at, times 12 LEDs, at the current the 25 ohm resistor allows to flow, which I solved graphically to get 200 mA. But, the voltage regulator, which gives a current equal to 1.25/R1 ohms, or, in this case, 1.25/2.5=500mA, which adds, 250 mA per string of LEDs, raising the voltage drop across the LEDs which reduces the current from the bypass circuit down to about 150 mA, leaving each LED with 400 mA of current, about where I want it to be. That makes the voltage regulator dissipate only .5 Amps x the 8 volt drop across it in power, or 4 watts. But, I don't need all of that extra 8 volts for the regulator to function - 3-3.5 volts is plenty. So, I can put a load resistor in the Vin line to the regulator to drop 4.5-5 volts, reducing the power dissipated to only 4 x .5 = 2watts, which the built in heat sink should handle easily. That load resistor would be about 10 ohms, with a rating of 10 watts (very conservative). And, that makes the circuit be:









And, of course, this will possibly still present a problem. If the resistors are all at the wrong end of their tolerance bands, I may not have enough voltage left to operate the voltage regulator. How, do I avoid that?

EDIT: I found that RadioShack has a heat sink for these, that is supposed to dissipate 5 watts, so I can omit the 10 ohm load resistor. I think this "stream of consciousness" design process may be completed!!


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## 691175002

Honestly I would avoid a shunt resistor and go with just an LM317 (or better, a 1V dropout version).

Grab a few 1A rated diodes to drop the current (each diode will drop .7V), use a 1V dropout regulator (http://www.national.com/mpf/LM/LM1084.html is one of many). This way you have 100% regulation and could be dissipating as little as .7W which might not even need a heatsink.

My concern with a resistor is that as the LEDs forward voltage changes with temperature the resistor will pass more or less current. The effect will be less than only using a resistor, but as long as you have the heatsinking most linear regulators can safely dissipate 30W+.

The LM1084 should be a drop in replacement for the LM317.


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## Hoppy

I can't find data on the effect of temperature on forward voltage. Do you have a link to that?


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## 691175002

I don't think it is normally included on datasheets, but it does happen:








If you get unlucky this can lead to thermal runaway since hotter means it will be getting more current.


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## Hoppy

Clearly it would be simpler to change to a different voltage regulator. So, I tried to figure out how to use the LM 1084 version:










This seems to work ok, with the 7 ohm voltage dropping resistor ahead of the voltage regulator. The effect of the LEDs getting up to 100C would be to reduce their voltage drop, thus increasing the power dissipated by the voltage regulator to about 8 watts, which would allow it to get very hot, shutting itself down. That isn't nearly as bad as the LEDs doing a thermal runaway. The voltage regulator would stop any thermal runaway, then shut off the lights. If the heat sink is effective enough the voltage regulator takes care of the whole problem.

I would love to bolt the voltage regulator to the LED heat sink, but that won't work because that heat sink has to be grounded, not held at about 40 volts - the heatsink lug on the voltage regulator is at the potential of the output voltage of the voltage regulator. I suppose I could look for a way to electrically insulate that lug, but still attach it to the LED heat sink - I feel a headache coming on!

Another headache: my trip to the electronics surplus store didn't result in finding a 48 volt adapter. That seems to be because no computer uses 48 volts, and most of the surplus stuff is salvaged from old computers and similar equipment. So, I may have to use ebay again. I did find a nice cheap one there, in a caseless, open package, which I would have to enclose someway for safety. http://cgi.ebay.com/55-watt-AC-to-D...5|66:2|65:12|39:1|240:1318|301:0|293:1|294:50


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## sunfire99

I have several TO 220 heatsink isolation hardware packages that will isolate the tab from it's heatsink. Be happy to drop it in an envelope to you. I also have tons of parts to build a simple transistor based regulator like the one attached. Just modify the base voltage which in that schematic is set at 7.4 volts. There will be ~.7volt drop to the output from where you set the base voltage with a zener. I don't have 45 volt zener diodes but have huge quantities of smaller ones that can be installed in series to make a 44 or 45 volt zener. I have several 7 to 15 watt resistors in various values as well and hundreds of 1/2watt in virtally every value. I've had this stuff in boxes for years. If you want to go this route, I can put it all in a padded mailer. You're probably tired of the new ideas, but as 691175002 already stated, these kind of regulator circuits are very simple and reliable. If you want to look at specs, I have some NTE152 transistors that would work for this application, rated at 4 amps and up to 90 volts. Let me know, at least it wouldn't cost you anything.


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## Hoppy

Steve, I PMed you. Your help and 691175002's help have been what has made it possible for me to keep going on this project. Thank both of you very much.


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## Hilde

What is the tolal cost of the project at present?


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## Hoppy

Hilde said:


> What is the tolal cost of the project at present?


I no longer know the actual cost, since I have wasted so much on blind alleys and outright mistakes. I have ordered my second 48 volt power supply, and have my 3rd current limiter half together. Then, there is the cost of the enclosure I built, which isn't specific to the LED light fixture. When I get through I may go back to try to find the cost for someone to reproduce just the fixture. I am pretty sure that will be between $150 and $200.

Last night I did a rough design and cost breakdown for a LED module, 9 inches square, with 9 LEDs like I'm using, mounted 3 inches apart, including a built in 12 VDC power supply, a driver circuit, heat sink, and cooling fan. That came to less than $100. Once I finally get this thing working, and know it will continue to work, I will probably start a thread offering my "design" for that module.


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## Hoppy

I disassembled my light fixture today, in readiness for the next attempt. I found that one of the FET's used in the constant current unit was badly overheated. The "heat sink" tab on it was permanently discolored blue. I suspect whatever caused the 3 LEDs in a row to stop working, caused the voltage drop across that string to decrease by 25%, which made the constant current device dissipate more power and overheat.

I had been planning to just ignore the fact that one string now has 9 working LEDs and the other has 12, but obviously that will be a problem with my new current limiter too. In fact, my calculations/ graphing shows that the 9 LED string will run at almost the entire 800 mA current, while the 12 LED string just barely glows at about 40 mA. I could balance that with a voltage dropping resistor in series with the 9 LED string, but that would only work at that one current, and I am setup to have my DPDT switch working to select either 800 mA or 400 mA total current to the two strings. So, I'm wondering if I'm going to have to buy 3 more LEDs and wait another 3 weeks to get them.


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## Hoppy

More progress: I "found" a 10 volt DC adapter (actually the adapter for a utterly useless electric gadget my wife got on sale), so I made a LED tester with it. I soldered a 15 ohm 3 watt resistor on the positive 10 VDC lead, and thickened the negative lead by tinning it. Then used red nail polish to mark the resistor lead as the positive lead. Using this I tested each of the 3 dead LED's which should have given me about 400 mA, but none of them lit up. So, I dug down deep for some nerve, and tested one LED that did work - it lit up very brightly. Just to be sure, I used my multimeter-ohmeter to test the resistance across the bad ones, and it was essential zero. Those three had failed shorted. I ordered 3 more LEDs from DealExtreme. I still don't know why the 3 failed in the first place, but I do now know they are completely dead, and in the worst way - shorted.


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## sunfire99

Well that sucks. I sure hope you get this all figred out so the rest of us can coast through a build.


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## Cactus Bastard

Hoppy said:


> I still don't know why the 3 failed in the first place, but I do now know they are completely dead, and in the worst way - shorted.


That's rather interesting. I recall hearing that it's more common for LEDs to fail open.


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## Hoppy

Cactus Bastard said:


> That's rather interesting. I recall hearing that it's more common for LEDs to fail open.


When I researched this I found that there are a few failure modes that result in a short through the LED. The real mystery is how 3 in a row at one end of a series string would have the same failure.

One thing I have learned is that it doesn't pay to build in the light fixture so you can't see or touch all of the electrical components for troubleshooting. I now plan to mount the driver circuit on the back of the heat sink, and mount the 48 volt DC adapter also on the back of the heat sink, so I will be able to remove the whole fixture, turn it over and run it while checking voltages at various spots. If I had a cheap little one amp ammeter I would mount that on the back too, to verify that the current I expect really exists. Since I have to wait over a week to get the replacement LEDs I may look into that part some more.


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## Wasserpest

What is your opinion about building a LED fixture using LED bulbs that are already in a housing? The bulbs itself would be more expensive, but you wouldn't need some of the materials (heatsink, power supplies etc) so in the end it would probably come out to be the same.

I am talking about bulbs like these (requiring a 12V power supply) or even these which can just be connected to line voltage. Just giving an example, not endorsing that specific source.

I know it would take a lot of fun out of the project, but for those that are not comfortable with transistors and capacitors as much, but still okay with electricity in general, it might be another option to a LED light fixture for smaller tanks.


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## 691175002

Wasserpest said:


> What is your opinion about building a LED fixture using LED bulbs that are already in a housing? The bulbs itself would be more expensive, but you wouldn't need some of the materials (heatsink, power supplies etc) so in the end it would probably come out to be the same.
> 
> I am talking about bulbs like these (requiring a 12V power supply) or even these which can just be connected to line voltage. Just giving an example, not endorsing that specific source.
> 
> I know it would take a lot of fun out of the project, but for those that are not comfortable with transistors and capacitors as much, but still okay with electricity in general, it might be another option to a LED light fixture for smaller tanks.


Both of your links only output 3W. Buying an equivalent (and likely brighter since you can overdrive them slightly) LED will run around 4$ even after shipping.

You will need 20+ of these bulbs and will end up paying along the lines of triple what the build would cost otherwise. You might not even be able to pack enough bulbs into the enclosure since they take up so much space.


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## Wasserpest

You are correct, however, two thoughts - 1) I mentioned small tank, perhaps smaller than Hoppy's project here, and 2) I thought Hoppy was actually going to underdrive them, since it would be too much PAR/wattage/intensity with the setup as described. 

I'd assume that say 8 of them could be enough to light a 10gal tank for example.


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## 691175002

It will absolutely work; but I think that the added cost is hard to justify. For example, loose LEDs can just be screwed into a piece of sheet aluminium. Mounting each bulb in a socket will be more work, money, and complicate the enclosure.

In all honesty, even the complexity of the electronics will be pretty similar. You are only omitting the driver which you can just buy premade. All you are getting is the exact same LED except with a reflector and driver tacked on.


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## Hoppy

One of the big advantages of LEDs is that they distribute the light source across the top of the tank. This gives uniform lighting on the substrate, but more important, it defeats the inverse square relationship between brightness and distance from the light. You just can't get close to a spread out light source like you can to a linear tube light source, so the intensity doesn't get so high near the water surface, and that will help a lot to eliminate algae problems. If you use "bulbs" which gather multiple LEDs into a small area, you lose that benefit. I think this is where a DIY light fixture will always be better.


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## Hoppy

Thanks to Sunfire99 I now have an electrical isolation kit for mounting my voltage regulator to the LED heat sink. That 5 pounds or so of aluminum should be able to keep the teeny little device cool enough.


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## Craigthor

Looking good Hoppy hope you get the kinks all worked out. Sure you mentioned earlier and I must have skimmed over it but any reason not to jsut buy the buck pucks (drivers) pre built?

Craig


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## Hoppy

Craigthor said:


> Looking good Hoppy hope you get the kinks all worked out. Sure you mentioned earlier and I must have skimmed over it but any reason not to jsut buy the buck pucks (drivers) pre built?
> 
> Craig


There are three compelling reasons not to buy the pre-built drivers. 
1. $$$$$
2. $$$$$$$
3. $$$$$$$$

Other than that, those are the best way to go.


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## Craigthor

Cool, I know the buck pucks are only around $15 Here is an 700Ma DC Buckpuck.

http://www.ledsupply.com/03021-d-e-700.php

I'm looking into using these for my project once I have a bit of positive cash flow. The 700Ma will run 18 1 watters or 6 3 watters.


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## Hoppy

Craigthor said:


> Cool, I know the buck pucks are only around $15 Here is an 700Ma DC Buckpuck.
> 
> http://www.ledsupply.com/03021-d-e-700.php
> 
> I'm looking into using these for my project once I have a bit of positive cash flow. The 700Ma will run 18 1 watters or 6 3 watters.


I am using 24 LEDs, so I would need 3 of those buck pucks, or $45 worth. That would be a significant increase in my costs. And, that is why I decided to try very hard to DIY the drivers.

Here is a progress report:










This shows where I am with it right now. The big electronic device is a new 48 volt power adapter, this time mounted on the heat sink where it will get some cooling air. The other two devices are the current setting resistors, which let me select either 425 mAmps or half of that per parallel string. If one string fails open circuit, the other gets 850 mAmp maximum, which is still acceptable. And the third, farthest from the camera is a tiny IC voltage regulator, using the fixture heat sink as its heat sink. This is the active device that provides the constant current.

Now, I need to get a surplus wire harness with a couple of Molex connectors on it, to mate with the power adapter, install the wiring out to the wall plug, and replace the 3 failed LEDs, which should arrive within 10 days or so.


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## sunfire99

Looking good!! I hope the slow boat from China with those LEDs gets here sooner than later. I'm anxious to see this work out so I can steal, I mean borrow, your plans.


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## Hoppy

Another progress report: I have all of the electric/electronic stuff hooked up now, and the power supply works. Since 3 of the LEDs are shorted I soldered a 15 ohm resistor in the circuit that is short 3 LEDs, and plugged it in. I got weak glow on the other string of 12 LEDs, and very bright on 3 LEDs in the 9 LED string. I unplugged that very fast! Then did an individual test of all of the 9 LEDs with my DIY tester, this time with 30 ohms in series with the 10 volts, and each LED works fine. So, now I just have to be patient and wait for the replacement 3 LEDs to arrive - they were shipped.

I'll admit this has become pretty frustrating.


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## evilc66

You are on the home stretch now though.


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## Hoppy

evilc66 said:


> You are on the home stretch now though.


I hope so:icon_cry: This is been a marathon!


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## Hilde

At the link for the light read that it is a soft white light that gives of 240 lumens at 350mA and 435 lumens at 700mA.

Can you grow red plants with this light? Is for low light plants?


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## malaybiswas

You can grow red plants with those. Good thing about diy led is that you can easily integrate a dimmer in the equation to control intensity with moving the fixture. That way you can adjust it and grow high or low light plants as and when you want.

Good going Hoppy. It has been lengthy no doubt but lot of valuable info as well. This one should be a sticky.

One learning from my fixture about uniform spread of light. Stem plants tend to grow on all directions instead of one. But then again if the fixture does not span the entire length & breadth, you can shift it horizontally to increase the intensity on one side forcing the plants to grow in that direction.


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## Hoppy

A subtle benefit is the lower intensity near the top of the water compared to tubular lights, which give very high intensity right under the tube, right at the top of the tank.

Hilde, there is no direct correlation between lumens and PAR. The 240 lumens can produce a very high PAR, if you use a lens to get all of that light into a small area, or very low PAR if you don't use a lens, and have the fixture mounted far from the substrate. And, that 240 lumens includes the light emitted at nearly a right angle to the direction the LED is "pointing", but most of that part of light never gets into the water. Also, the light intensity on the axis of the LED is quite a bit higher in PAR than that off the axis, which can cause a bad "spotlight" effect if the LEDs are spaced too far apart. It looks to me like my 3" spacing, with no lenses, and with the LEDs about 20 inches from the substrate, is close to the maximum spacing that can be used without objectionable spotlighting. But, with the LEDs I'm using, much closer spacing would give too high a PAR for most planted tanks at that 20 inch distance (by my standards). There is just an awful lot to be learned about LEDs in order to do a good DIY fixture.


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## evilc66

Hoppy said:


> There is just an awful lot to be learned about LEDs in order to do a good DIY fixture.


You're not kidding. It's taken me about a year and a half to get all the intricacies straight for reef lighting with the use of two colors of LEDs, and the different optics thrown into the mix. Throw that on top of the thermal and electrical requirements and you have the potential for quite a mess on your hands. It has been worth it though.


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## Hoppy

evilc66 said:


> You're not kidding. It's taken me about a year and a half to get all the intricacies straight for reef lighting with the use of two colors of LEDs, and the different optics thrown into the mix. Throw that on top of the thermal and electrical requirements and you have the potential for quite a mess on your hands. It has been worth it though.


Those of us who do this have unique ways to relax after a day in the garage working on LEDs.


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## evilc66

:hihi: Sometimes it feels that way. You have to admit, the results are worth it. I have to get started on my freshwater LED setup, but there is something very different appearance wise with LEDs over a reef. Some have described it as "high def", but either way it's difficult to describe. Was it the same for you when you fired it up over the tank?


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## Hoppy

evilc66 said:


> :hihi: Sometimes it feels that way. You have to admit, the results are worth it. I have to get started on my freshwater LED setup, but there is something very different appearance wise with LEDs over a reef. Some have described it as "high def", but either way it's difficult to describe. Was it the same for you when you fired it up over the tank?


The short time it ran before burning out the power supply, it fascinated me. The shimmering shadow look on the substrate was almost hypnotic, to the point that I couldn't decide if I liked it or not. Then, I ran to get my camera, and when I got back the lights were off. I'm looking forward to getting a longer time to enjoy and study it next time, hopefully before this week is over.

I have tested each LED with about 200 mA current, using a 10 volt DC adapter with 30 ohms in series, low current, in other words, and the brightness is still awesome. I just touch the solder pads and it flashes like a photoflash. It flashes because I wince at the brightness, losing contact with the pads. These things seem like witchcraft, they are so intense. All of that light from an almost invisible point!


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## evilc66

Looks like another project to add to the list. One of these days the list is going to get smaller instead of bigger :icon_roll


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## original kuhli

Hoppy, have been watching this thread for a long time...kudo's to you for helping the community learn to 'do it on the cheap'. Your frustrations will pay off!


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## Hoppy

original kuhli said:


> Hoppy, have been watching this thread for a long time...kudo's to you for helping the community learn to 'do it on the cheap'. Your frustrations will pay off!


Thank you, I'm glad it has been helpful. Now, if only we could help DealExtreme row that canoe across the Pacific:icon_evil


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## Cactus Bastard

Hoppy said:


> The short time it ran before burning out the power supply, it fascinated me. The shimmering shadow look on the substrate was almost hypnotic, to the point that I couldn't decide if I liked it or not.


I put a single P7 on top of a 10 gallon, and found the shimmering to be a little overbearing. I think on a larger tank, with multiple light sources it wouldn't be as intense. Also the ten gallon, it was really high frequency, since the ripples had so little surface area.


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## Hoppy

I keep my water surface well rippled by directing a Koralia powerhead slightly upward. I'm a little bit anxious about whether that will produce a dizzying shimmer on the substrate. If so, I suppose I can reduce the ripple a little bit.


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## Hoppy

The replacement LEDs arrived yesterday, but it was much too hot to work in the garage, so I installed them this morning. The photo is with the current at about 200 mAmps. So bright it still dazzles my eyes 30 minutes later. I hope to get this back over the tank this afternoon to take some PAR measurements, see how much shimmer I get, and most critical of all, see if it will run all day. Wish me luck!


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## CL

Nice thread hoppy!
If the lights last this time, you might get a whole led movement going on pt.


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## Regloh

clwatkins10 said:


> Nice thread hoppy!
> If the lights last this time, you might get a whole led movement going on pt.


I'm on board... I think I have an opening for a new project the middle of 2011. Right after the controller, a new canopy, a second fish tank (in the office), the list goes on. But that's why we call it a hobby, right?

Looks really nice and bright hoppy. I can't wait to see the picture with it installed above the tank.


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## Hoppy

Running at 200 mAmps










Running at 400 mAmps

At 200 mAmps I measured 30 micromols PAR at 3" above the substrate, and at 400 mAmps, 45 micromols at the same location. At 200 mA I got about 45 micromols just below the water line, and at 400 mA I got about 100 micromols at that location, and about 80 micromols at about 4" below the water line. All of those measurements were in the middle of the tank.

The PAR remained constant just below the water line at about +/- 8 inches from the center going from end to end, and dropped in half right near the end. From front to back the PAR remained constant at about +/- 2" and gradually dropped to half at near the front and back. The plants kept me from making that type measurement further down in the tank.

At 400 mA I have about the PAR I was hoping for, possibly a bit low, but not much, and I can always lower the fixture a little to increase it. Right now the LEDs are 7 inches above the tank rim.

The shimmer is fascinating. Every leaf, every ripple and every fish casts multiple shadows on the substrate and the lower leaves. It is disconcerting at first, but in 30 minutes it didn't bother me. And, the light has been on about 30 miinutes now, with the heat sink not even feeling warm.

EDIT: The actual calculated current these are running at is 425 mA for each parallel string, or 850 mA total, for a total power consumption of 40 watts. The light intensity I'm getting is almost exactly what I was getting with a 55 watt GE9325K bulb in an AHS bright kit, mounted at the same location. So, this is using 73% of the power for the same amount of PAR.

Because the light is distributed over most of the footprint of the tank, and not coming from just a small area, the rise in intensity as you go up in the tank is not nearly an inverse square relationship, but is much closer to being linear. So, the intensity near the waterline isn't as high as I would expect from a typical aquarium light giving the same PAR at the substrate. (This is a good feature.)

It has been about an hour now, and the heatsink is still not even warm, and, of course, the lights are still working - a miracle!


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## Minsc

:thumbsup: Good to see it working, it is an awesome light fixture!

What are your thoughts on the color of the lights?
Also, in case I missed it, how old was the PC bulb you tested?


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## Hoppy

These are cool white LEDs, giving a crisp white, which looks to me like a 10,000K bulb or something like that. I like it, but I also like the GE9325K light, for different reasons. The LEDs bring out the "neon" like spots on my new black phantom tetras, but don't emphasize the reds in the white cloud mountain minnows. I have found before that my eyes quickly see almost all lighting about the same, even though they have different spectra. The GE bulb is about 18 months or so old, so it is not as efficient as it was originally. I can't guess its actual age, since I have two of them and run only one at a time. The actual age may be closer to a year.

Two hours, and they are still working, and the heatsink still isn't even warm.


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## Hoppy

I can't see any "spot lighting" effect from the individual LEDs, so I decided to look for it photographically. Here is a normal photo looking down at the substrate:









I can't see any spotlighting on that, so I tried cutting down the exposure, jacking up the constrast, and cutting down the brightness, to see if that will reveal any spotlight effect:









Even with that, I can't see any spotlighting. From that I think it is safe to say that a 3 inch on centers spacing of the LEDs works very well, at a distance of 20 inches or so. Perhaps at half that distance it might show spotlighting, but I can't tell about that without making the water cloudy so it shows the cones of light from the LEDs.


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## sunfire99

Congrats Hoppy.:icon_cool I bet it's a relief to have it working, and the fact that it does what you hoped has got to be rewarding for you.


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## Hoppy

sunfire99 said:


> Congrats Hoppy.:icon_cool I bet it's a relief to have it working, and the fact that it does what you hoped has got to be rewarding for you.


Yes, it is a relief, especially since it has been on for 6 hours now and is still working:bounce:

I now think I can predict what light will result from using these LEDs, for a range of conditions. Of course, using a different LED would make predicting just as hard as it was this time. I'm trying to work out an "instruction sheet" for designing a fixture for almost any tank using this LED. That should take only a couple or three days.


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## 691175002

Nice work, its good that it finally looks like its working. Even better, with that much heatsinking and only 400mA those LEDs should last nearly forever without degradation.

I've got my LED light finally running. 10 3W leds at 750mA and about 6W of assorted other LEDs. The entire fixture gets pretty hot without a fan since I thermal epoxied all of the linear regulators and some transistors to the case as well but I'm seeing pearling on the plants and its only a few hours in. 

My LEDs are probably going to go downhill in a year or so but the microcontroller gives some nice sunrise/sunset effects.


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## Hoppy

The light fixture is still working fine, going on when the timer tells it to, and off when it tells it to do that. No burned out LEDs either. The shimmering shadows don't bother me at all. But, fish with reds don't show up as brilliantly as with the GE9325K bulb, leading me to wonder if a few weak red LEDs would be a good addition. (I wont try it due to the excessive complexity that would be needed.)


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## 691175002

Hoppy said:


> The light fixture is still working fine, going on when the timer tells it to, and off when it tells it to do that. No burned out LEDs either. The shimmering shadows don't bother me at all. But, fish with reds don't show up as brilliantly as with the GE9325K bulb, leading me to wonder if a few weak red LEDs would be a good addition. (I wont try it due to the excessive complexity that would be needed.)


I know what you mean, I actually disliked the spectrum of the cool white LEDs so much that I have about a hundred 5mm leds in yellow, red and green to even out the colors.

You can see the reflection of the light in the water:









If I were to do this again I would buy a random selection of cool, neutral and warm LEDs to have as varied a spectrum as possible.


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## evilc66

Glad things are doing well Hoppy. I think I will try my setup with neutral whites seeing as you are not getting reds to pop as much. They have pretty much the same blue output with a bit more red than the cool whites, but less than the warm whites. I have a bunch of both laying around, so I could mix and match if the neutrals don't work out.


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## redman88

hows that instruction sheet coming along


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## Hoppy

redman88 said:


> hows that instruction sheet coming along


Here is a start:
Designing a LED light fixture 
to produce 100 micromols per square meter per second PAR.

Using my data plus the data given by Cree for their LEDs, I made these charts:










Notice that as you get closer than about 20 inches from the LEDs, the inverse square relationship between intensity and distance switches to much closer to a linear relationship (intensity = 1/ distance instead of intensity = 1/ distance squared). The pink line is for the first setup of the LEDs when they were running at some much higher current than 400 mA, and quickly burned out the power supply. The black line is for the current 400 mA LED setup, plus some data from my AHSupply fixture.



















To use this for designing a fixture to give 100 micromols PAR, first, decide how far from the substrate you want the LEDs to be? Let’s assume you want that to be 22 inches.

How much LED current do you want to use? At 700 mA or less, the LEDs should last for at least a few years. Higher current will reduce the life of the LEDs. Let’s assume you want to use 700 mA current.

My LED array gives about 55 micromols of PAR at about 22 inches, with 700 mA current. (Determined by studying those charts) You will need 100/55 or 1.8 times more light. To get that you need to space the LEDs closer together to get more of them illuminating each square inch of the substrate.

My LEDs are spaced at 3 inches on centers, or .11 LEDs per square inch of the fixture. Increasing that to 1.8 x .11 or .20 LEDs per square inch, will give the needed PAR. With my tank, that would require 4 rows of 11 LEDs instead of 3 rows of 8 LEDs. And the spacing would be 2.25 inches. 










A good heat sink, fully capable of handling this array of LEDs can be made from 2 inch width aluminum channel, http://tinyurl.com/nuf5op, or equivalent purchased locally. Four 24 inch lengths would be needed, which from the ebay source, would cost about $50. These could be bolted together, side by side, separated with 1/8” thick spacers, to make about a 8 3/4 inch wide heat sink.

For different foot print tanks you can adjust the number of LEDs to cover the foot print. For a 55 gallon tank, for example, 48” x 12.5”, the heat sink could be the same 8 3/4 inches wide, but 42 inches long, requiring 4 rows of 18 LEDs, 72 total.

You can also use brighter LEDs. For example you could use the Q5 version of that Cree LED and get 22% more light per LED, or use the best Luxeon Star and get about double the light per LED. Using these brighter LEDs lets you use fewer of them, but I suggest not getting them farther apart than 3 inches, to avoid any spotlighting effects.

Still to come: mounting the LEDs and determining how to power them.


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## JDowns

I would think that if you used the Q5's at the same configuration or more per square inch with a dimmer to bring down the mA value to achieve the same par should extend the life of the lamps and reduce heat (heat shouldn't be a concern though).

Great thread Hoppy. Really makes me want to do a LED build, looks like fun.


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## Hoppy

JDowns said:


> I would think that if you used the Q5's at the same configuration or more per square inch with a dimmer to bring down the mA value to achieve the same par should extend the life of the lamps and reduce heat (heat shouldn't be a concern though).
> 
> Great thread Hoppy. Really makes me want to do a LED build, looks like fun.


Thank you, it is a lot of fun. I had about 4 months of enjoyment from spending around $250 on this, and I spent several hours almost every day of that time on it. If I were to have used that money to eat out with the wife, all I would have to show for it would be a bigger belly! (Save this argument, it might win you one some day:biggrin: )

Using Q5 LEDs at a lower current would give the same result, but I think once you get below 700 mA or so you don't gain much more in life. My current of about 400 mA is already way below that. I don't think we need the higher power, higher efficiency LEDs for planted tanks, unless they are very high ones, perhaps 30+ inches. Otherwise we just have too much light, or we get spotlight effects. Reef tanks are another subject, and I'm sure the higher output LEDs are very useful for that.


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## Minsc

Hoppy said:


> If I were to have used that money to eat out with the wife, all I would have to show for it would be a bigger belly! (Save this argument, it might win you one some day:biggrin: )


I'm not sure about this argument Hoppy. It sounds like, "I could have taken you on 5 nice dates, but instead I have some glowing doodads above my fishtank!"
Might not be the best go to justification:icon_wink

Thanks for the charts, this thread is getting bookmarked for sure!


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## Hoppy

Minsc said:


> I'm not sure about this argument Hoppy. It sounds like, "I could have taken you on 5 nice dates, but instead I have some glowing doodads above my fishtank!"
> Might not be the best go to justification:icon_wink
> 
> Thanks for the charts, this thread is getting bookmarked for sure!


Good point! I think I will rewrite my script before trying this again.


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## 691175002

A breif scan of the cree reliability document says that if you keep the LED cooler than 80C it will last 50,000 hours before dropping to 70% its original output. That comes to around 14 years of 10 hours a day light.

From what I remember, the thermal resistance of the LEDs are around 8C/W which means that if you run it at a full 2.4W (3.4V*0.7A) it will be at around 20C hotter than its heatsink. In extreme conditions, you can have your heatsink at nearly 60C and have the LEDs last virtually indefinitely even at higher current levels.

LEDs running at 400mA with an ambient temperature of 30C probably have 20 years or more in them of 80%+ output.

When it comes to powering LEDs I have just discovered the many driver ICs manufacturers have available. I used a generic LM317 circuit but if I were to do it again I would use some of the LED specific components.

Most of them boast 90%+ efficiency, a whole slew of protective features for short/open circuits and overheating, built in dimming and more.


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## Hoppy

Powering LED Light Fixtures

LEDs require a DC power supply, and an electronic device to provide a constant current to the LEDs from that power supply. Automobiles use 12 volt DC power for everything, with a socket or sockets available for plugging in 12 VDC appliances, from radios and cell phones to camping equipment like mini-refrigerators. To make those appliances usable on standard 110 VAC circuits there are many AC to DC adapters available, including this one, http://tinyurl.com/mfn7vo , which costs only about $25, and which will provide 5 amps (5000mA) of 12DC current. This is a good source of power for multi LED lights.

Each Cree LED drops 3.5 volts across it when operating at 700 mA current. A 12 volt source will, therefore, power only 3 of those LEDs in series, but strings of 3 LEDs in series can be wired in parallel up to a total of 5000 mA/700 mA = 7 strings in parallel. That means one of those 12 VDC power supplies can power 3 x 7 = 21 LEDs.

The 100 micromol PAR fixture we are designing requires 44 LEDs, but reducing that to 42 will have negligible effect, so we can use two circuits, each with 21 LEDs running at 700 mA for the fixture.

LED drivers are the electronic devices that connect the DC power to the LEDs to run them at a chosen constant current. There are many commercial LED drivers available, but, for 700 mA current, at a cost of roughly $5 per LED, more than doubling the cost of the LEDs for a light fixture. This suggests that a DIY driver is a better option.

A simple, inexpensive and effective LED driver can be made from an IC adjustable voltage regulator, and the most widely available cheap voltage regulator is the LM1084IS-ADJ, sold by Newark Electronics, http://tinyurl.com/lba8b9

This tiny integrated circuit device can be mounted on the heat sink, using an electric isolator package, http://tinyurl.com/lna4zq to allow heat to be conducted to the heat sink, but not electric current. Adding one resistor, and possibly a couple of capacitors will enable this tiny device to act as a constant current controller for about 6 of the LEDs, so 7 of them will be required, but each costs about $3.00, or about $0.50 per LED, one tenth of the cost of a commercial driver. The voltage limiter is connected as shown:









The R1 resistor sets the constant current provided by the voltage regulator, and that current is equal to 1.25 divided by the value of the resistor in ohms. To get 700 mA for each of the two parallel strings, or 1.4 Amps total current would require .89 ohms, which is not a resistor value that is available, but 2-1.8 ohm resistors, http://tinyurl.com/kqe4fn in parallel give .9 ohm, which results in 1.42 Amps or 710 mA current per LED. This simple circuit will work adequately as long as the DC power supply is kept within about 6 inches from the voltage regulator. If the DC power supply is located farther away, a couple of little capacitors are needed to avoid excessive fluctuations in the LED current.


----------



## Hoppy

Mounting and cooling LEDs

LEDs require a heat sink to keep them from overheating and destroying themselves. For a big light fixture, a heat sink made from aluminum channel extrusions, bolted side by side to give the width needed, works very well, and is much less expensive than finned heat sinks made for that purpose. It is helpful to use about 1/8 inch thick aluminum spacers between the channels to provide space for cooling air to flow around each channel. 

After bolting the channels together, use silicon carbide sandpaper wrapped around a wood block to sand the faces flat, and polish them with finer grades of silicon carbide paper. The objective is to get as perfect a contact between the LED “star” mountings and the heat sink as is possible.

The “star” mountings have notches around them to allow holding them in place with #4 size screws, and flat head screws, normally countersunk, are the best type of screw for this purpose, because they cannot accidentally contact the very close by solder pads on the “star” mounts. Drilling and tapping the holes to fit #4 screws is very easy, using a cordless screw driver or drill. 

First mark lines along the heat sink where the LEDs will be located. Then mark a spot 3/8” (9.5 mm) on each side of that line on the centerline for each LED. Use a center punch to make a small indentation on each mark. Drill a 3/32 inch diameter hole through the heat sink at each location. (Extreme accuracy is not needed.) Use the cordless screw driver, or cordless drill with speed control, to slowly tap the hole with a #4-40 tap. It works best to turn the tap a few times, back it off to remove the aluminum particles from the tap, then finish tapping the hole. Working with aluminum is much easier than working with steel, so it is very unlikely that you will break the tap.

Use silicon carbide paper, a fine grade, to flatten the areas where the drilling and tapping raised the metal, and polish again with finer grade paper. Clean the heat sink surface with alcohol until no more powdered aluminum rubs off.

To get better heat transfer between the LED “star” mounts and the heat sink, use a thermal compound on both the heat sink surface and the back surface of the LED. There are now many such compounds available, but one of the best for the money is Antec Formula 5, which comes in a big enough tube to mount about 50 or so LEDs. Fry’s Electronics stocks it. Use only a tiny amount on each surface, a dot of the compound, spread a little with the nozzle of the tube. Rotate the LED slightly as you lay it in place to further spread the compound, and attach the LED with 1/2” long #4-40 flat head screws. (The length of the screws isn’t important, but needs to be long enough to handle easily.)

EDIT: It appears that Cree star mounts do not well insulate the conductive core of the circuit board from the mounting notches. This can be a problem, because the flathead screws put a pretty strong force on the corner of the notches, and that may result in electrical contact between the screw, and therefore the heatsink ground, and the LED electric contacts. I recommend not using screws at all, but using an adhesive thermal paste to mount the stars, such as http://www.arcticsilver.com/arctic_alumina_thermal_adhesive.htm

The heat sink will slowly get hotter and hotter, with the light fixture on, unless a cooling fan or fans are used to help transfer the heat to the air. Mounting the fans above the heat sink, blowing down on the back of it, works fine. This gentle cooling breeze will also help keep the AC-DC converters and voltage regulators cool, if they are mounted on or above heat sink.

Use short lengths of 22 gage insulated wire to connect the LEDs in series, in groups of 3, for this particular design, and longer lengths to make the parallel connections behind the heat sink. Soldering is easiest using a solder with a small amount of silver in it, and resin core, http://tinyurl.com/nhgvxf plus a small soldering iron, http://tinyurl.com/6dxbsh

You now know just about all that I know about making a relatively cheap LED light fixture. Try it. It's fun!


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## Wasserpest

Allow me to sticky this for now... excellent write-up Hoppy. roud:


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## CL

Congratulations on the sticky 
There's a lot of excellent info in this thread


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## Hoppy

Wow! Thank you. I just hope somebody will use this to make their own light.


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## redman88

already started to order the parts. spent 65ish dollars so far thats including shiping though i don't have to shipping on a few of the items yet. just need to order the LED's
(bump)

i am going to attempt to do this with just 21 LED's over a 29 gallon see how that works for me if needed i should be able to upgrade with another 21 at a later date


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## Hoppy

Well, the "adventure" isn't over:icon_sad:

Yesterday morning the lights came on as the timer told them to. A few minutes later as I was starting to add the day's ferts, the lights suddenly dimmed. Only 6 LEDs, in one of the 12 LED series groups, remained on, with all 6 being together, the 1st thru 6th from the + lead. The other series group were all off. I disconnected it after checking that the cooling fans were on, and stewed about this the rest of the day.

This morning I tested the LEDs individually, and they all work, so it isn't a failure of LEDs.

I'm stumped, but I do have some ideas about the problem. Here is a question for the electronics skilled members here: If I run 3 LEDs in series, use a constant current device to provide them with 400 mA current, all 3 LEDs will light up as 400 mA current goes through them. Now, suppose my power supply voltage drops below 3X the forward voltage of each LED - for example, if they each run at 3.5 volts at 400 mA (10.5 volts total in series), and my power supply output drops to 10 volts, what happens and why?

I always think in terms of resistors in series or parallel, just from intuition. That thinking says the currrent drops until the voltage available equals the total voltage drop across the LEDs. But, the constant current device won't allow that to happen, so the current goes to zero. (?) With LEDs, each LED will drop the voltage available to the next one in series by 3.5 volts, so the first two will be ok, but the third one only gets 3 volts, which is too little. What does it do, and why? Will a LED supplied with current, but inadequate voltage pass the current along, but not light up?

In my actual circuit, I have about 45 volts available for total forward voltages of the LEDs in series, and 12 in series, each needing 3.5 volts, or 42 volts total. But, suppose a questionable solder joint adds a resistance in the circuit, dropping 20 volts at 400 mA? Would that allow 6 LEDs to light up, but leave the last 6 in the series just passing current without lighting up?

Any other ideas?

EDIT: I just found 3 solder joints at LEDs that were questionable, one of which I could break loose by hand. I resoldered the 3 connections, but that didn't help. Also, I realized that the "-" connection to the two series strings of LEDs is ground, and the heat sink is grounded. So, any current leakage to ground, perhaps at the 6th LED that is lit up, would shut down the last 6 of that string, and that string would then hog the current, leaving the other string underpowered, so it would be off. It may be that my soldering is the total cause of this problem, with the resistance at one or more joints increasing, or bits of solder making a connection to the heat sink, etc. causing the "failure". It is becoming obvious that a 15 watt soldering iron isn't up to doing a good job on mounted LEDs, so I may end up buying a 25 watt one.


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## Hoppy

Progress: The only type of failure I have been able to think of is a grounded LED in the string that has 6 lit up LEDs, so those "downstream" from that grounded one get no current through them, and the other string gets too little current to light up, since most of the current goes to the lower total voltage drop string with the ground.

Hip, hip, hurrah! Thanks to the troubleshooting tips from an experienced LED hobbyist on the Barr Report, I found the problem! First, I disconnected the ground connection to the string that didn't light up at all. Plugged it in, and nothing changed. So, I reconnected that ground, and disconnected the ground to the string that had the 6 still operating LEDs. Plugged it in, and the same 6 continued to be the only ones lit up. This had to mean there was a grounded LED in that string. So, I removed the mounting screws for the last lit up LED and placed a piece of paper behind it to keep if off the heatsink. Plugged it in, and the previously unlit string came on fully, and the string that had the 6 still lit ones was dark. Absolute proof that that LED was shorted to ground at the "-" end of it. I still can't see anything wrong on it, nothing to show that it is grounded, but there is no question that it was grounded. To double check this, I then reconnected both grounds, so both strings had the "-" end grounded, but left the faulty LED separated from the heat sink. Plugged it in, and both strings light up fully.

My tentative guess is that moisture between the star mount and the heatsink may have been involved, or the star mounting is not well done by the assembler. Tomorrow I will figure out what next. Any suggestions? Is there a relatively easy way to electrically isolate that one - with a mica shim, for example? Or would it then overheat?


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## JDowns

Mica would work, or Ferrite.

Here is just one link of grease epoxies that would probably work in your operating temperature ranges, giving you good heat transfer and electrical isolation.

http://www.epoxies.com/therm.htm


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## JDowns

I would call them for a recommendation given your application and then order a sample for evaluation.


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## Hoppy

So, the epoxy thermal compounds are good electrical insulators but also good thermal conductors. Frys has several types of thermal compounds in stock, so I may visit there and pick up the best one. I sure don't want to wait for some one to ship it. That is a good idea though. Sometimes you get so close to a project you can't see the things right in front of your face!


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## JDowns

There are quite a few epoxies that are very good at thermal conductivity while also being electrically isolated. Just not sure what your operating temperatures are at.

I would think you could apply the epoxy to your heatsink, let dry, then mount the star.

Frys more than likely carries such a compound or grease. I haven't personally looked in my hours of wandering the store looking for ways to waste money, but its probably worth a look 


Another type product

http://www.omega.com/pptst/OB-100_OB-200_OT-200.html

A thin film of the OB-200-2 and that 2oz should go a long way.


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## Hoppy

Problem solved - for now anyway. The "failure" was current leakage to ground through the "line" contact where the screws held the one LED to the heat sink. Looking very carefully I can see slight discoloration around the screw notch in the star mount, where it contacted the conical back face of the screw head.

Today I found some Arctic Silver brand alumina filled epoxy heat conductive cement at Frys. I thoroughly cleaned the heat sink in the contact area, cleaned the back of the LED (using alcohol), and reinstalled the LED using the alumna filled epoxy. After a half hour (it sets up in 5 minutes) I plugged it back in, and only the 6 LEDs ahead of the failed one lit up. So, I removed the attaching screws entirely. Plugged it in again, and it worked fine. That is when I looked for and found the discoloration.

Now I suspect that I will get this failure again, as another LED leaks current at that spot. If so, I will then mount all of the LEDs with the ceramic epoxy and not use screws at all. In the future I won't try to use the screws if I make another one of these.


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## JDowns

Hoppy said:


> Problem solved - for now anyway. The "failure" was current leakage to ground through the "line" contact where the screws held the one LED to the heat sink. Looking very carefully I can see slight discoloration around the screw notch in the star mount, where it contacted the conical back face of the screw head.
> 
> Today I found some Arctic Silver brand alumina filled epoxy heat conductive cement at Frys. I thoroughly cleaned the heat sink in the contact area, cleaned the back of the LED (using alcohol), and reinstalled the LED using the alumna filled epoxy. After a half hour (it sets up in 5 minutes) I plugged it back in, and only the 6 LEDs ahead of the failed one lit up. So, I removed the attaching screws entirely. Plugged it in again, and it worked fine. That is when I looked for and found the discoloration.
> 
> Now I suspect that I will get this failure again, as another LED leaks current at that spot. If so, I will then mount all of the LEDs with the ceramic epoxy and not use screws at all. In the future I won't try to use the screws if I make another one of these.


 
You can still use the screws. Just use ceramic washers as a barrier. 

Glad to see you got it fixed.


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## Hoppy

JDowns said:


> You can still use the screws. Just use ceramic washers as a barrier.
> 
> Glad to see you got it fixed.


Back during another "debate" over how to mount the LEDs, by another DIYer, he chose to use a silicone material to mount the stars. In retrospect I think that was a better idea than screws. It is true that you can use insulating washers, and bushings, to separate the screw from the star, but that is very much harder to do. For one thing, the notches are designed to fit #4 diameter screws, but with an insulating bushing, you would need smaller diameter screws, hard to find and much harder to drill and tap for. I would rather just use adhesive, easy and simple. Here is the one I used: http://www.arcticsilver.com/arctic_alumina_thermal_adhesive.htm Time will tell whether this was a good choice.

For a reef light, needing the LEDs to be driven at near maximum current, I think it would be worth the added effort to use insulated screws, but for our use, the heat that has to pass from the LED to the heat sink is much less and a lesser thermal compound should work fine.


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## evilc66

You can always use nylon screws.


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## Regloh

Nylon can only take 180-230F long term. If your fixture stays below that you are in the clear... 
I have used ceramic screws before, but those are not really affordable on a DIY project


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## xpistalpetex

hey hoppy if possible can you do a step by step wiring?


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## Hoppy

xpistalpetex said:


> hey hoppy if possible can you do a step by step wiring?


Yes, I probably can, but I don't have a photo that shows the wiring well. Let me see if I can work up a drawing that will be clear.


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## xpistalpetex

ooo thank you sir


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## Hoppy

Step by step wiring:
1. Having attached all of the LEDs to the heatsink, making sure they are lined up with the positive ends facing the right direction - towards where the positive lead from the power will come, solder the LEDs into two series chains of 12 each, using short pieces of insulated wire. Connect negative end to next positive end, etc.

2. Attach IC Voltage Regulator, a tiny little thing, to the heatsink with a electrical isolation pad between it and the heatsink, and an electrical isolation bushing in the Voltage Regulator mounting hole.

3. Solder a 47 or 100 microfarad capacitor, preferably one that doesn't have a positive and negative lead, across the "Vout" and "Adj" terminals of the Voltage Regulator.

4. Select the current setting resistor, by dividing 1.25 by the desired current (twice the current per LED, since this will be for two parallel circuits.) Pick the closest standard resistor to the value you determined. Solder one lead from each resistor together, to put them in a series string.

5. Solder the connected ends to one end terminal of the DPDT switch (SPDT works fine).

6. Solder one of the remaining resistor leads to the other end terminal of the DPDT switch.

7. Solder the other remaining resistor lead to the "Adj" terminal of the voltage regulator.

8. Solder a wire connecting the center terminal of the DPDT switch to the "Vout" terminal of the voltage regulator.

9. The 48 volt DC power adapter has a row of pins at one end - 6 as I recall. Solder a wire from the second or third of those pins to the "Vin" terminal of the voltage regulator.

10. Solder two long lengths of wire together at one end, and solder that connected pair to the "Adj" terminal of the Voltage Regulator.

11. Solder the other end of one of those long wires to the first positive solder pad on the first in the string of LEDs. Solder the other end of the other long wire to the other first positive solder pad on the other string of LEDs.

12. Solder short wires to the negative solder pads of the two end LEDs in the two strings, and connect them to a grounding screw in the heat sink.

13. Solder a ground wire to the ground terminal of the 48 VDC power adapter, and attach the other end to a grounding screw on the heat sink.

14. Solder the green ground wire of the 120 VAC power cable to the ground terminal on the 48 VDC power adapter, or attach it to the grounding screw on the heat sink.

15. Connect the black and white wires of the 120 VAC power cable to the power in terminals on the 48 VDC power adapter.

16. Wiring is complete. Double check your fire insurance before plugging this in the first time:hihi:


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## VisionQuest28

Man, im so intrigued by this idea and LED lighting in general. I would love to put one of these together, but i think, scratch that... i know, i would be in WAAAAAAY over my head. I just dont think i could afford to learn as i go and pay to replace the things i messed up! I am searching out and buying the LED light strips made by current called PowerBrite's for a 10 gallon im setting up. Just got one on ebay for about $30, would like one more main unit and then i need to find the linking modules. Think im gonna end up with an intensely lit tank in the 16w range...im excited!

But what i would really like to do is set up LED's on the 36 gallon corner bowfront i have. Was planning on doing MH lighting, mainly because its such an odd shaped tank its hard to get an even spread of light. As soon as i saw this thread i started thinking about using LEDs on that tank. If i had the know how i would put one of these together in the shape i needed. But since i dont ive been looking at some of the already made LED panels on ebay mostly. The price is about equivalent to buying MH, maybe even a little less, especially when you consider electric costs and heat issues. Im just hesitant because i dont know if the panels would provide the right color temp/spread/and intensity im looking for.

I guess my point to all of this is.... you the man Hoppy! Such a cool DIY! I agree that LEDs are the future of lighting, and you got in there on the ground floor. Way to go!


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## Hoppy

VisionQuest28 said:


> Man, im so intrigued by this idea and LED lighting in general. I would love to put one of these together, but i think, scratch that... i know, i would be in WAAAAAAY over my head. I just dont think i could afford to learn as i go and pay to replace the things i messed up! I am searching out and buying the LED light strips made by current called PowerBrite's for a 10 gallon im setting up. Just got one on ebay for about $30, would like one more main unit and then i need to find the linking modules. Think im gonna end up with an intensely lit tank in the 16w range...im excited!
> 
> But what i would really like to do is set up LED's on the 36 gallon corner bowfront i have. Was planning on doing MH lighting, mainly because its such an odd shaped tank its hard to get an even spread of light. As soon as i saw this thread i started thinking about using LEDs on that tank. If i had the know how i would put one of these together in the shape i needed. But since i dont ive been looking at some of the already made LED panels on ebay mostly. The price is about equivalent to buying MH, maybe even a little less, especially when you consider electric costs and heat issues. Im just hesitant because i dont know if the panels would provide the right color temp/spread/and intensity im looking for.
> 
> I guess my point to all of this is.... you the man Hoppy! Such a cool DIY! I agree that LEDs are the future of lighting, and you got in there on the ground floor. Way to go!


When the question about lighting a bowfront, 24" on a side, came up I started to see if it could be done reasonably. Here is the layout that I figured would give enough light for most plants, but I didn't go ahead with figuring out a circuit for this.









This would use the same 3" x 1" aluminum channel I used for mine, for a heat sink. If you want to look into it some more I could go ahead and figure out a good circuit.


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## 4f1hmi

Thank you Hoppy for your very informative thread.


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## VisionQuest28

Hoppy said:


> When the question about lighting a bowfront, 24" on a side, came up I started to see if it could be done reasonably. Here is the layout that I figured would give enough light for most plants, but I didn't go ahead with figuring out a circuit for this.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> This would use the same 3" x 1" aluminum channel I used for mine, for a heat sink. If you want to look into it some more I could go ahead and figure out a good circuit.


Im certainly interested, and thanks for showing that lay out for a bowfront. If it was a really involved thing, i would say hold off on any figuring for a circuit. Im a ways out from doing anything with this tank, as im still gathering other equipment. You made your own power supply for yours right? I think i would be willing to pay a little extra for an already available power supply, mainly because that would save me a lot of headache. I think i could work the rest out (assuming you'd be willing to hold my hand the whole way! lol) by myself or atleast know a person or two that might be able to help. 

Did you do any playing around with different colored LEDs? I think if i remember right you went with all 10,000k right? And i rememeber you saying that you had thought about adding in red, but that it has unpredictable results sometimes. Could you explain that any more? 

Id so love to be able to build this myself. I know th elevel of satisfaction you must feel is huge!


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## Hoppy

With 45 LEDs the "drivers" for the LEDs could cost quite a lot if you buy them, and you would still need a source of DC power. Given how simple it is to make your own "driver" circuit, and how cheap it is, it is well worth the struggle to do so.

I will work out some kind of circuit or circuits that will work with this, and you can decide for yourself if you want to tackle it.

I use all "cool white" Cree LEDs, which don't have a lot of red in their spectra. Theoretically you could mix cool white with warm white and get better color rendition, but I haven't tried it so I'm not sure how well the light from the LEDs would mix. Adding red LEDs is another possibility, but I already know from the experience of others that it is very hard to avoid seeing the red beams of light when you do that.


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## VisionQuest28

Ok, thats awesome, thanks. I can get my potential helper(s) to look it over and see what they think. Whats your opinion on the different optics that can be mounted over the LEDs? Would that be a way to get the different colors to mix better? Ive looked at some, when i was looking into adding a little bit of red to the 10g with powerbrites, and the prices didnt seem bad, but i wasnt thinking about 45 of them either.


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## Hoppy

VisionQuest28 said:


> Ok, thats awesome, thanks. I can get my potential helper(s) to look it over and see what they think. Whats your opinion on the different optics that can be mounted over the LEDs? Would that be a way to get the different colors to mix better? Ive looked at some, when i was looking into adding a little bit of red to the 10g with powerbrites, and the prices didnt seem bad, but i wasnt thinking about 45 of them either.


As best I can tell, all of the lenses made for LEDs are to get less spread of the light, so you can get more intensity at greater distances. But, our objective is to get wide spread of the light from each LED so they blend in and add to the total intensity at every spot in the tank. So, I wouldn't consider any optics at all.

Here is a diagram of one way to connect all of the 45 LEDs. 









Finding the parts can be a challenge. The little IC Voltage Regulators are not widely available now, being considered obsolete, but also being perfect for this application. Many are still available, but it appears that you need to get a quote on the specific number you want from the seller. I googled to find out about this. Newark Electronics doesn't seem to carry them anymore.

The AC to 12 Volt DC adapters are sold for people to use to power their 12 volt accessories normally powered by their car power socket. So, they are pretty widely available, and ebay has several. They need to have about 5 amp capacity to avoid overheating with the continuous 3.5 amp current each will be supplying.

The 47 microfarad capacitors are standard parts that RadioShack and other stores carry. But, make sure they are not polarized - no + and - leads.

The single hardest part of this is mounting the voltage regulators, which are only 0.4 inch by 0.5 inch by 0.2 inch in size, onto the heat sink, and keeping the big mounting lug electrically isolated from the heat sink, but thermally connected to it. This means using a mica sheet between the lug and the heat sink, and a plastic bushing in the mounting hole. There are kits available with these parts: TO-220 mounting kits. Then soldering wires to the voltage regulator leads, which are close together, isn't easy either. But, all of the rest is fairly easy.

This circuit is designed to get 750 mAmps current for each LED. If one LED fails, the current to the remaining 12 LEDs in that group will increase to 940 mAmps, which is still within the limit for these LEDs.

And the LEDs are these: http://www.dealextreme.com/details.dx/sku.2395 or others in that series.


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## VisionQuest28

Hoppy...my head is spinning! And you make it all sound so easy. haha Ive spent the last several hours looking over stuff online, and i GUESS i have a little better understanding now.

That circuit diagram doesnt show the power supply, right, or does it? And the voltage regulators, capacitors, and resistors are what would make up a driver? The equivalent would be something like a BuckPuck?

And the way you're showing the LEDs obviously isnt the same as i would have them mounted. But as long as they are in 3 groups of 15, with 5 parallel strings of 3 LEDs in each group, i could follow that diagram, yes?

I said i was in over my head, and i think thats even more true than ever. But i would really like to figure this out. I remember you saying what an obsession this turned into for you, and i can certainly see how this would be true. Luckily for me (and anyone else who is thinking about doing this) you have laid the ground work to make this remotely possible for me to even consider doing. Thanks for that! And thanks for taking the time to help with what you have already!


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## VisionQuest28

never mind about the power source, thats what the 12 VDC adapter is, i got it. Given a little more time ill probably get my answer to the buckpuck too. But if you get here first.... haha


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## Hoppy

As best I can tell a buck puck is similar to the Voltage Regulator/Resistor/capacitor circuit. I suspect it is different, probably using transistors instead of the Voltage Regulator. In any case, yes the VR + Resistor + Capacitor serves the function of the buck puck, but a lot cheaper. And, if you haven't figured it out yet, that sketch isn't to scale. The 12 VDC adapters (power supplies) are about 1" x 2" x 4", while the Voltage regulator is closer to .5" x .4" x .15". They are much smaller than you will ever expect!

And, yes, I showed the LEDs in that configuration just to make the wiring look easier. In your case it will look different. The principles involved are not all that difficult to grasp, but I found it all to be non-intuitive, so I felt like a very slow learner trying to understand it.


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## VisionQuest28

From the time i last posted i just sat down and re-read this whole thread, and if i do this im definitely gonna spend the money on buck puck's or something similar. After seeing all the problems you had, the extra $40 or so to just buy it and be done with it seems SOOOO worth it me. I just dont think i have the knowledge or skill to do it the same way you did. But im still very interested in trying this. Even with buying parts instead of making them, the cost to benefit ratio still seems good to me.


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## VisionQuest28

691175002 said:


> I know what you mean, I actually disliked the spectrum of the cool white LEDs so much that I have about a hundred 5mm leds in yellow, red and green to even out the colors.
> 
> You can see the reflection of the light in the water:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> If I were to do this again I would buy a random selection of cool, neutral and warm LEDs to have as varied a spectrum as possible.


This is an idea ive been considering. How do you feel adding in all those 5mm LED's worked out? Are you happy with the appearance? Do you have a FTS with them? Even better...a FTS with just the white LED's and another with the multiple 5mm adding in for comparison???


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## kev82

buckpucks are not similar to this, they are buck regulators. They get the same (similar) end result, but with significantly different means.
http://www.controleng.com/blog/Ask_Control_Engineering/14267-How_does_a_buck_regulator_work_.php


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## VisionQuest28

kev82 said:


> buckpucks are not similar to this, they are buck regulators. They get the same (similar) end result, but with significantly different means.
> http://www.controleng.com/blog/Ask_Control_Engineering/14267-How_does_a_buck_regulator_work_.php


I must admit, reading through that...its almost like a foreign language, but i guess i understand what they are saying, just not why. haha But knowing these will work and will eliminate a lot pieces/connections/solder points...thats what i really want to know. And im willing to pay for it. Im confused though....are buckpucks drivers AND power supplies? Ive seen tech data referring to these as power supplies and ive seen others in this thread say you would still need a power supply if you used these. Do they mean the AC/DC adapter?


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## Hoppy

VisionQuest28 said:


> I must admit, reading through that...its almost like a foreign language, but i guess i understand what they are saying, just not why. haha But knowing these will work and will eliminate a lot pieces/connections/solder points...thats what i really want to know. And im willing to pay for it. Im confused though....are buckpucks drivers AND power supplies? Ive seen tech data referring to these as power supplies and ive seen others in this thread say you would still need a power supply if you used these. Do they mean the AC/DC adapter?


You have to provide a DC voltage to the buck puck. It maintains a constant current, which you select, through the LEDs that are connected to it. The "weakness" of using buck pucks is that each one will only control a fairly small number of LEDs, so you need several buck pucks, and they aren't very cheap yet. They most definitely do make hooking up LEDs easier and more likely to work as you expect them to.

EDIT: http://shop.ebay.com/items/?_nkw=LED+driver&_armrs=1&_from=
If I had found this before I made my light, and wanted to spend the time figuring out how each one would work, this is how I would have obtained drivers for the LEDs. Some pretty good prices here.


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## VisionQuest28

Hoppy said:


> EDIT: http://shop.ebay.com/items/?_nkw=LED+driver&_armrs=1&_from=
> If I had found this before I made my light, and wanted to spend the time figuring out how each one would work, this is how I would have obtained drivers for the LEDs. Some pretty good prices here.


Care to point out one or two that you think are a good buy? Would some of the higher wattage drivers be able run all of the LED's, instead of having to use several buck pucks? I think 3 buck pucks can be had for about $50, and from what i saw the higher wattage drivers looked to be around the same price. Any other benefit to using one driver instead of 3?


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## Hoppy

VisionQuest28 said:


> Care to point out one or two that you think are a good buy? Would some of the higher wattage drivers be able run all of the LED's, instead of having to use several buck pucks? I think 3 buck pucks can be had for about $50, and from what i saw the higher wattage drivers looked to be around the same price. Any other benefit to using one driver instead of 3?


I didn't study the listings well enough to decide which I thought were the best buys. And, I have some more learning to do before I would attempt to recommend one anyway. The pictorial circuit diagram is just one way to connect 45 of those LEDs and power them. There must be another 10 ways, some of which would be better, and some not so good. And, a lot would depend on how important low cost is to you, and how willing you are to take some risks as you learn.

Until this lighting method gets a lot more standardized, I think any of us who try it will need to do a lot of studying to be sure we understand how any circuit we use works, so we can recognize most of the dumb mistakes we would otherwise make. I was willing to make mistakes, and did make many, and I wanted to learn as much as I could, so that didn't bother me either. But, I also wanted to go about as cheaply as I could, which isn't everyone's desire. And, that last was the reason for most of my mistakes.


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## VisionQuest28

Hoppy...i hear what you're saying. Not exactly that im going to just have to figure it out for myself, but kind of. lol And thats cool. Im somewhere in between wanting to learn what i can from this AND being willing to spend some extra cash to avoid all the potential mistakes that i KNOW i would make.

This corner bowfront is such a weird shape, and its pretty tough to get an even spread of light over it. Thats one of the main reasons im considering the LED route. But im also very intrigued by it, and think thats the way everything will be heading in the years to come. As far as costs go i was looking at MH lighting, possibly supplemented by either florescents or T5's...so i was prepared to drop some $$$ on my lighting. Ive yet to sit down and figure the rough costs of attempting the DIY LED's using as many premade parts as possible, but as long as its in the same ball park as going the alternative route i had planned, im happy with that.

Im actually in the process of getting myself enrolled in some new career training for becoming an electrical maintenance technician. Classes start the end of August, so this hopefully wont all be so foreign to me soon. I might just get a good head start on a lot of what im going to learn from researching this. Thanks for evereything...


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## Hoppy

VisionQuest28 said:


> Im actually in the process of getting myself enrolled in some new career training for becoming an electrical maintenance technician. Classes start the end of August, so this hopefully wont all be so foreign to me soon. I might just get a good head start on a lot of what im going to learn from researching this. Thanks for everything...


When you start building your own LED fixture, please post a DIY article as you go along, so we can all learn from your experience. Reading about other's projects was what helped me the most in my adventure. Notice, I didn't say "if" you build your own - I sense another fellow LED addict in the making:redface:


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## VisionQuest28

Hoppy said:


> When you start building your own LED fixture, please post a DIY article as you go along, so we can all learn from your experience. Reading about other's projects was what helped me the most in my adventure. Notice, I didn't say "if" you build your own - I sense another fellow LED addict in the making:redface:


I think you're definitely right Hoppy, i have been bit by the bug for sure! I will definitely start a thread,i agree with you. I think everyone who does this should make it available to all of us...the more people who see it and want to do it, the more ideas and brains we have to make it better. Once i finish putting my co2 system together i think im going to but the LED's..then there will be no turning back i will HAVE to do something with them. lol


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## VisionQuest28

Just cuz this has been quiet for awhile now...i start my electrical maintenance classes in 2 weeks, and once i get a decent background going i will definitely be starting to work on some LED project!

I have been using a PowerBrite LED strip over my 37g non planted (technically doesnt fit this category any more) to light an area where i am attempting to keep java moss and fern. I would really like to pick up a couple more of these, i REALLY love them. Im torn between buying them now while they are still on sale or waiting until i can build my own. I might just end up doing both! lol


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## Hoppy

There was a news article today, on Yahoo, about some group learning to make LEDs as a very thin sheet, so they could be used as a contoured tail light for a car, or an advertising sign on a bus, right over the windows, since they are so thin you can see through them. Of course, my mind wandered off to thinking about covering the sides of an aquarium with such a LED film, so you look through the lights to see the tank.

But, back to the real world, my LED fixture just keeps on working. I'm now running it only at the low light setting on the switch, since I'm trying to convert the plants to growing in a low tech, low light environment. No CO2 now either. I plan to use the fixture on a 65 gallon tank to be set up as a riparium in a few weeks.


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## CL

Sweet sauce! And you can run them at full blaze for the plants to soak up the lights, and you won't have to worry about the heat wilting the plants! :thumbsup:


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## jestep

Hate to jump into a post so late like this. 

But, what was the reasoning you chose series wiring vs. parallel wiring?

Both have their advantages and disadvantages. I'm just curious as to why you chose series vs parallel for this project. Assuming that it was a conscious decision, and not just what seemed easiest. Anyway, great chronology of what you've done so far.

_Obviously this is a parallel circuit. I've seen many LED wiring diagrams using much more of a parallel layout, like one or two LED's per series._


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## Hoppy

Choosing the right circuit to use is a matter of matching the power supply voltage to the LED voltage needs. If you use 5 volt power supplies, obviously you need a separate supply for each LED - not good. But, if you go with a high voltage supply, you generate more problems with isolating the voltage, with finding other components to match, etc. So, I compromised on the 48 volt supply, and was able to find a couple of places to buy one at a good price. In retrospect I would probably use multiple 12 volt supplies. 

Once you have the voltage selected, it works best to put enough LEDs in series to use as much of that voltage as you can, unless you spend more on "buck puck" type drivers, where the excess voltage is not dissipated as heat. That is what led me to the series circuit. And, the total number of LEDs divided by the number I could run in series, led to using the three parallel circuits.

When you really DIY a Led light you have so many decisions you can make that it is dizzying to figure it all out.


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## plantbrain

Hoppy, I think I can do this and make it look good for about 110$ for my 60 Cube and very little time.

This will = 28 Watts for a 60 Gal tank, or about 0.45w/gal.

I'll let you know and takes some pics, Get some PAR data with the meter.

Give me a week or so.

Regards,

Tom Barr


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## jarthel

Hi Hoppy. Do you think 24 LEDs is enough? I believe you have a 2ft setup so that's 12 LEDs per foot? thank you


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## Hoppy

jarthel said:


> Hi Hoppy. Do you think 24 LEDs is enough? I believe you have a 2ft setup so that's 12 LEDs per foot? thank you


Mine was made for a 30 inch long tank, about 20 inches high, as I recall. I no longer have that tank. I was aiming for low light intensity at the substrate, with the light about 6 inches above the top of the tank. And, I came pretty close to what I expected. It is the spacing of the LEDs that counts, not the number per foot. That is spacing in both directions. The spacing controls how many individual LEDs contribute light to any square inch of the substrate. I think I used 3 inch spacing for mine. Closer would give more light, and farther apart would give less light. And, of course closer means more LEDs to cover the area. I intentionally didn't try to cover the entire tank footprint, leaving a few inches all around with no LED directly above. That was because I had, by then, decided I wanted my future aquascapes to feature an "island" of plants in the middle with the outside edges free of any high plants, for better water circulation.


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## Hoppy

plantbrain said:


> Hoppy, I think I can do this and make it look good for about 110$ for my 60 Cube and very little time.
> 
> This will = 28 Watts for a 60 Gal tank, or about 0.45w/gal.
> 
> I'll let you know and takes some pics, Get some PAR data with the meter.
> 
> Give me a week or so.
> 
> Regards,
> 
> Tom Barr


Tom, I'm looking forward to that! $110 would be a miracle, well worth a thread here describing how you did it.


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## original kuhli

I'm intereseted in hearing how Tom made out with his LED fixture...any progress?


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## ryanlogic

*maybe this will help*

this guy makes some awesome LED stuff. and there is a plethora of information surrounding his threads. i promise this stuff will be useful to anyone thinking about building a DIY led fixture.

http://www.nano-reef.com/forums/index.php?showtopic=186982

http://www.nano-reef.com/forums/index.php?showtopic=200335


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## trag

ryanlogic said:


> this guy makes some awesome LED stuff. and there is a plethora of information surrounding his threads. i promise this stuff will be useful to anyone thinking about building a DIY led fixture.


Ryan, you evil, evil person. Following those links I spent weeks reading the lengthy threads, and the related threads and even more linked-to LED threads over on reef central forums. And now I feel compelled to design and build my own LED drivers (neither Meanwells, nor BuckPucks are quite satisfactory). Arrrggggghhhhhh. 

I have enough projects...


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## Hoppy

I just finished getting a lot of PAR data with some cheap 1 watt LEDs from Ebay. As a result I think I can do a much better job of predicting the light output we can get from either the Cree or the Ebay LEDs. See http://www.plantedtank.net/forums/lighting/108678-cheap-led-light.html for details.


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## Hoppy

After weeks of thinking about this, and searching for ways to predict how multiple LEDs spread out over a tank produce a given amount of PAR, I finally found a good way to do it. This involves some data I collected with the PAR meter, using just one LED, but measuring the PAR vs the offset from under the LED, at several distances from the LED, plus some measurements of PAR with my Cree LED fixture, and some measurements from small grids of 1 watt LEDs at various distances. For Cree XR-E LEDs I ended up with this chart, which I verified against the output I get with my fixture.









This is based on using a grid of LEDs at the top of the tank, at either 10 inches or 20 inches from the substrate. You can interpolate for other distances. And I only considered grids with a spacing from 2 to 4 inches - smaller is impractical and larger doesn't give uniform light, nor enough of it. The grid should extend to within about one half of the spacing from each glass side/end. For example, for a 10 gallon tank, with a 10 x 20 inch top, if you wanted 80 micromols of PAR at the substrate, 10 inches below the light, you could use 4 inch spacing between LEDs, or a 2 x 6 LED grid, expecting to use about 600 mAmp LED current. With any LED fixture you really need to measure the PAR you get, then adjust the current or the height of the fixture to get the PAR you want.


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## Fish'InMN

Is there any way for you to repeat this measurement process with optics?


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## Hoppy

Optics don't change anything, except for making the intensity less uniform. At worst optics would give you a spot of light under each LED and almost no light between the spots. Without the optics, every spot on the substrate gets light from at least 9 LEDs, up to about 25 with the LEDs spaced 2 inches apart. But, with the optics each spot on the substrate gets light almost entirely from one LED. If the tank is very high, more than 30 inches, for example, not having optics might cause a loss of too much light through the glass sides, but not for 20 inch or lower tanks, at least as far as I can tell.


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## Fish'InMN

... Which could be proven with data collected in the same manner, but without is only anecdotal.


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## S&KGray

Thanks again Hoppy for the wealth of information.

I have a question about a 2 x 6 LED grid working for a 16g bowfront. Its footprint is similar to a 10g, about a 9.75" x 20" not including the bow. At the middle of the tank, front to back is about 12.25". The height of the tank is about 18 inches.

The reason I am asking is the housing I have to work with only has about a 4.5" x 13" footprint for the grid. So 6 LEDs in a row could be spaced 2.25" apart from each other at most, and the 2 rows could be spaced 2.8" apart at most. Any thoughts?


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## Hoppy

S&KGray said:


> Thanks again Hoppy for the wealth of information.
> 
> I have a question about a 2 x 6 LED grid working for a 16g bowfront. Its footprint is similar to a 10g, about a 9.75" x 20" not including the bow. At the middle of the tank, front to back is about 12.25". The height of the tank is about 18 inches.
> 
> The reason I am asking is the housing I have to work with only has about a 4.5" x 13" footprint for the grid. So 6 LEDs in a row could be spaced 2.25" apart from each other at most, and the 2 rows could be spaced 2.8" apart at most. Any thoughts?


I was just thinking about this today while I was supposed to be doing something else. My data for grids of 1 watt LEDs showed that the intensity is a maximum right under the middle of the grid, dropping off about 20% as you get near the edge of the grid. Obviously as you get beyond the edge of the grid the drop off is much greater. A 2 x 6 grid on a 12" depth tank would likely have very low light near the front and back glasses. This is because the cone of light from an LED is pretty small compared to a T5HO light, for example, so you don't get much light once you are outside that cone. At about 4 inches from the centerline of a 1 watt LED, 6 inches from the LED, the intensity is only about 25% of what it is at the centerline, and it drops rapidly beyond 4 inches. 

Maybe if that 2 x 6 grid had the LED's spaced at about 3 inches along the length of the tank, but about 5-6 inches along the depth of the tank, it might work. It would probably be low light though. Calculating how much light you would get is pretty laborious and easy to get lost in, so I haven't tried calculating what this grid would do.


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## S&KGray

I will have to design a new housing and grid to space the LEDs better and maybe use more LEDs. The current parts I am using to build the housing limits me to a 4.5" x 13" area for placing the LEDs. I may still build this and try it out, and if it doesn't work well I can use it on a smaller tank.

I am thinking about using Cree XP-Gs running at 1A so I can raise the fixture several inches above the tank to get more even spread of light. Also the XP-Gs have a 125 degree viewing angle vs the XR-Es 90 degree, but I don't think that will make much of a difference...


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## Hoppy

S&KGray said:


> I will have to design a new housing and grid to space the LEDs better and maybe use more LEDs. The current parts I am using to build the housing limits me to a 4.5" x 13" area for placing the LEDs. I may still build this and try it out, and if it doesn't work well I can use it on a smaller tank.
> 
> I am thinking about using Cree XP-Gs running at 1A so I can raise the fixture several inches above the tank to get more even spread of light. Also the XP-Gs have a 125 degree viewing angle vs the XR-Es 90 degree, but I don't think that will make much of a difference...


Be sure to start a thread on building that light. There is so little data available on LED lights for planted tanks that any additional data is very valuable. If at all possible, use a PAR meter to measure how much light you get.


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## Hilde

So how much has it cost you so far? Where are you on the project?


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## Hoppy

Hilde said:


> So how much has it cost you so far? Where are you on the project?


Is that directed at SK Gray?


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## S&KGray

I just ordered my LED's and driver PCB's this past weekend. I am still deciding whether to dish out the money for a large 1-piece aluminum heatsink, try to find aluminum u-channel for cheap, or use small individual heatsinks.


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## Hilde

Hoppy said:


> Is that directed at SK Gray?


 No! You Hoppy. This is your thread and you are making a LED fixture?

Just came across this thread about someone building a LED fixture by Supercoley1


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## Hoppy

My LED fixture was done long ago, and has been in use since then. I don't recall the total cost, but it was in the neighborhood of $200.


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## Hilde

Hoppy said:


> My LED fixture was done long ago, and has been in use since then. I don't recall the total cost, but it was in the neighborhood of $200.


How long do you estimate that the bulbs will last? Are you going to be injecting Co2?


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## Hoppy

LEDs are not "bulbs". They are tiny little semiconductor devices, encased in clear plastic for protection and to act as a lens. I have no way to even guess how long they will last - it should be for several years.

I made my fixture to get low light, where CO2 would be optional. For about 6 months I used it with CO2, but now it is lighting a riparium, in a bigger tank, with no CO2.


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## Gibby

Hi everyone.

Hoppy this is a very informative thread and I have just lost half a day of my life reading it!

I wondered if, instead of fans, anyone had thought of using a small diameter line with a pump for water cooling instead of the fans? If the water is returned to the tank then you would be getting some heating for the cost of the pump.

Also, does anyone know of someone doing a large version of this? I'm looking to do a 64" x 30" x 28" ex-reef with sump so any advice would be extremely helpful. Looking at store bought units I reckon I could spend over £1500 easily and still not have enough light! Ideally I would like to keep the number of plug sockets used to a minimum.

I was hoping to have a clear perspex sheet above the water, the LED's mounted on aluminium as per Hoppy's design, possibly with the water cooling, then some form of lid to top it off. The unit will sit on top of the tank rim which is 2.5" from the water surface so the LED's are probably going to be around 3"-4" from the water surface.

If nobody has gone this big before then I will definitely start a new thread for those who would like to do a larger build.


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## Hoppy

Gibby said:


> Hi everyone.
> 
> Hoppy this is a very informative thread and I have just lost half a day of my life reading it!
> 
> I wondered if, instead of fans, anyone had thought of using a small diameter line with a pump for water cooling instead of the fans? If the water is returned to the tank then you would be getting some heating for the cost of the pump.
> 
> Also, does anyone know of someone doing a large version of this? I'm looking to do a 64" x 30" x 28" ex-reef with sump so any advice would be extremely helpful. Looking at store bought units I reckon I could spend over £1500 easily and still not have enough light! Ideally I would like to keep the number of plug sockets used to a minimum.
> 
> I was hoping to have a clear perspex sheet above the water, the LED's mounted on aluminium as per Hoppy's design, possibly with the water cooling, then some form of lid to top it off. The unit will sit on top of the tank rim which is 2.5" from the water surface so the LED's are probably going to be around 3"-4" from the water surface.
> 
> If nobody has gone this big before then I will definitely start a new thread for those who would like to do a larger build.


There is no way to make an economical LED fixture for a tank that big, with the LEDs being about 28 inches from the substrate. You can certainly fit enough of those Cree 3 watt LEDs into such a fixture, but it is going to be very expensive just for the LEDs, and even more so when you add in the cost of the driver circuits and power supplies. If good 3 watt LEDs were available for $1 apiece it might be economical, but they are more like $5 each.

If you don't mind spending money fast, there is enough information in this http://www.plantedtank.net/forums/diy/84212-designing-building-led-fixture-22.html#post1102937 to be able to design something that would be pretty close to what you need, just considering the LEDs. The driver circuit(s) are another matter needing a lot of design time. Just don't be fooled into believing that adding lenses to the LEDs will make it easier.


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## DMtankd

Hi Hoppy,

Thank you again for posting so much useful information.

Looking at your lighting chart - it looks like the inverse square rule doesn't apply.

For instance, if I compare the expected PAR at 10 and 20 inches for, say, the 4 inch grid interval running at 800 mA - I read an approximate PAR value of 100 at 10 inches and about 60 at 20 inches.

I would expect that, if the light is producing a PAR value of 100 at 10 inches, it should be producing somewhere around 25 at 20 inches. Am I missing something?


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## Hoppy

The inverse square relationship breaks down with a highly distributed light source like a grid of LEDs. One reason is the relatively narrow beam of light you get from each LED, which lets only some of the LEDs light any specific spot on the substrate, until you move quite a long distance from the grid of LEDs. Look at a 55 gallon tank, for example, There is no way for any of the light from the left side LEDs to shine on any of the right side substrate. At 10 inches from the LEDs, only about 25 LEDs on a 3 inch spaced grid can contribute to the light on any one spot, but at 20 inches, 4 times as many can contribute light.


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## CptanPanic

I have a few questions: How does the PAR of the LED's (Cree XR-E Q2) compare to similarly wattage T5's? In a PM, Hoppy mentioned he would recommend an array of 36 for a 55gallon, with 400mA for Low Light, and 800mA for High Light, this seems a bit low since at 400mA comes out to 50W, I would have expected LED's to much more efficient that florescent's, what is the difference?


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## Hilde

CptanPanic said:


> How does the PAR of the LED's compare to similarly wattage T5's?


I have a feeling it is like comparing oranges to tangerine. For the light from LED's is different from the T5's, for read they cause a simmering affect. The spectrums are closer to sunlight than T5s.


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## Hoppy

Hilde said:


> I have a feeling it is like comparing oranges to tangerine. For the light from LED's is different from the T5's, for read they cause a simmering affect. The spectrums are closer to sunlight than T5s.


Actually LED light can look exactly like T5 light, depending on the phosphors used in the LED and the T5 light. LEDs give a small beam of light, with almost all of the emitted light inside of that beam. T5's, like any fluorescent bulb produce light in all directions, and rely on a good reflector to capture much of the light and direct it to the aquarium. T5HO lights, with the typical one bulb reflectors made of highly polished aluminum, are very efficient light sources. I don't really know how their efficiency, as far as PAR in the aquarium goes, compares with LEDs.

One LED doesn't give enough light for even a small tank, and what it gives is in a small beam that doesn't cover much of the substrate. They work for an aquarium because you can use lots of them, each contributing at least a little light to every part of the substrate. (For LEDs that are some distance to the side of a particular spot, their contribution is trivial.) Getting enough light for a given tank is just a matter of how closely you space the LEDs, when using the Cree 3 watt LEDs.


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## redfishsc

Hoppy, just found this thread (again), loved it. 

I'm much more of a "just buy the Meanwell driver" kind of guy-- I do not know the technical know-how or time to build the DIY driver like you did (esp since a Meanwell 60-48 is now about $32). 


Right now I'm planning the lighting for that 70g tank (23X23X31). 

I have 26 LEDs (royal blue XREs and cool white XPG) all with 60 degree lenses. 

By my calculations I should be able to put these on a 12X12 heatsink, with multiple fans, with them about 5" above the water line--- and still get good spread on the middle/bottom. 

I'm not so worried about spotlighting up top--- the only thing that would be making it that high would be some val or maybe a lotus leaf.

You mentioned that I'd be getting around 20-40ppfd, where did you come up with that calculation (not that I doubt it--- I've never tested a tank this deep).

Right now with the light about 22" from the substrate (and only 12 LEDs at that) I'm getting around 90-100ppfd with 12" water depth.


I may pick up locally a few more drivers and LEDs to bump the LED count up to 39.


BTW I highly recommend people try to mix colors up a tad (no more than 3 colors unless you want ugly spotlighting). 


I'm going to try to mix cool white, royal blue, and possibly cyan. Maybe 3-4 reds (without optics for wide spread) just for looks.


Maybe 13 cool white XPG
and 13 royal blue XRE (already have these)
then add 6 neutral/warm whites and 7 cyans.


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## Hoppy

redfishsc said:


> Hoppy, just found this thread (again), loved it.
> 
> I'm much more of a "just buy the Meanwell driver" kind of guy-- I do not know the technical know-how or time to build the DIY driver like you did (esp since a Meanwell 60-48 is now about $32).
> 
> 
> Right now I'm planning the lighting for that 70g tank (23X23X31).
> 
> I have 26 LEDs (royal blue XREs and cool white XPG) all with 60 degree lenses.
> 
> By my calculations I should be able to put these on a 12X12 heatsink, with multiple fans, with them about 5" above the water line--- and still get good spread on the middle/bottom.
> 
> I'm not so worried about spotlighting up top--- the only thing that would be making it that high would be some val or maybe a lotus leaf.
> 
> *You mentioned that I'd be getting around 20-40ppfd, where did you come up with that calculation (not that I doubt it--- I've never tested a tank this deep).*
> 
> Right now with the light about 22" from the substrate (and only 12 LEDs at that) I'm getting around 90-100ppfd with 12" water depth.
> 
> 
> I may pick up locally a few more drivers and LEDs to bump the LED count up to 39.
> 
> 
> BTW I highly recommend people try to mix colors up a tad (no more than 3 colors unless you want ugly spotlighting).
> 
> 
> I'm going to try to mix cool white, royal blue, and possibly cyan. Maybe 3-4 reds (without optics for wide spread) just for looks.
> 
> 
> Maybe 13 cool white XPG
> and 13 royal blue XRE (already have these)
> then add 6 neutral/warm whites and 7 cyans.


I'm not real sure I can work backwards from my last chart to exactly how I made the chart.








Then, I had to extrapolate both in distance and in LED current to get your configuration. I will be happy if my answer is accurate within +/-50% But.for now, that's the best I can do.


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## redfishsc

Thanks! Does this data include the use of optics (60-degree in my case)?

In your graph, it says 10" or 20" from substrate. Is that supposed to say "surface" instead?


I'm getting data similar to what you're showing in the plot (under 10-12 LEDs, my 10g only sits under half of the array right now, houseplants get the other).



I plan on spacing them more centered than spread out since I'll have 30+ inches for them to spread out (willing to deal with some shading or color spotlighting near the surface of the tank--- the top 3" will be hidden by my canopy to make it appear to be a 23" cube).



We will see what I get when it's done. I have access to a PAR meter but it's hit or miss. 


Hopefully I'll be picking up some more LEDs and drivers soon, locally there is a person that wants to sell me their array and I'll just add it to what I have. 


My next big problem is figuring out how to do 50% water changes on a tank holding around 50g of water.... when I live in a tiny apartment.... at least it's 1st floor and I have a cement patio. But that's another thread altogether.


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## Hoppy

redfishsc said:


> Thanks! Does this data include the use of optics (60-degree in my case)?
> 
> In your graph, it says 10" or 20" from substrate. Is that supposed to say "surface" instead?


No optics, other than the lens that protects the LED junction, are involved. I found that a more narrow beam was a detriment, not a benefit. And, I couldn't find any "wide angle" type add-on lens that produced more spread without distorting it too much.

PAR varies with distance from the source of light, so no one PAR number means anything, except when you include the distance from the light. I felt that the best place to measure it and specify it would be the substrate level in the tank. Also, it makes little difference whether there is air or water between the light and the PAR sensor, at least directly under the light. Water does tend to focus the light a bit, so the light at the substrate is more uniform than I would otherwise expect, and slightly higher in intensity.


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## redfishsc

Hoppy said:


> No optics, other than the lens that protects the LED junction, are involved. I found that a more narrow beam was a detriment, not a benefit. And, I couldn't find any "wide angle" type add-on lens that produced more spread without distorting it too much.


I've found that 60 degree optics dramatically increase the PAR levels but obviously decreases the coverage area... .which can be used to an advantage with the height of the array and/or dimming. 

It's the 60-degree optics that allow me to hit the same PAR numbers (and basically same coverage area) of a 250w DE halide (Phoenix bulb)-- using 26 LEDs and a rough estimate of 96-110 watts of usage (on a 24" long array). I have not found color spotlighting to be an issue but we'll see on the new build how it goes .



> PAR varies with distance from the source of light, so no one PAR number means anything, except when you include the distance from the light. I felt that the best place to measure it and specify it would be the substrate level in the tank. Also, it makes little difference whether there is air or water between the light and the PAR sensor, at least directly under the light. Water does tend to focus the light a bit, so the light at the substrate is more uniform than I would otherwise expect, and slightly higher in intensity.



Sorry, I did misunderstand you. You were talking about how far the LEDs were from the substrate. I was thinking (for whatever reason) that you were meaning to say how far the meter probe was from the surface.


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## JDowns

I just finished another LED build for an aquarium and ended up using 60° optics this time instead of 40° optics. For this build I opted for 1.5" x .75" x .125" aluminum "C" channel instead of 2" as I've used before. The 1.5" performs well with a minimal airflow and the array driven at 650ma. The total array was for essentially a 48" x 12" fixture with 3.5" spacing between each LED with 4 rows of 12. I used 2 Meanwell ELN 60-48D run in parallel series. Each Meanwell was preset to 44v @ 1.3a to run (2) ea strings of 12 splitting the amps to 650ma with a 1a fuse before each run. Running the array at 9.4v at the dimming control, with 60° optics, and the fixture 20" above the water surface. Average par measured at 40" was 180umols and at 30" was 340umols. What surprised me was the visual interpretation. First look made me feel as though the tank would have measured less par in comparision to the T5 fixture it replaced (3 x 80w), not triple the par output. 

I used a 50% mix of CW and NW Cree XR-E's. Still don't completely like the color output. It leans to much on the 10,000k side. Still playing with color balance at this point. Not much time for experimenting lately. Once my camera makes it back I'll get some photo's. But will definatly have to dial back considerably on the dimming input.


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## Hoppy

180 micromols at 40 inches from the LEDs? That is an amazingly high output for Cree XR-Es spaced at 3.5 inches. I'm confused now, for sure!

Yesterday I found this: a really cheap fixed current driver, http://www.dealextreme.com/details.dx/sku.42906 giving 650 mA at 28 to 45 volts DC. This will easily drive 12 of the Cree LEDs at 650 mA or 24 at 325 mA. Used with http://www.dealextreme.com/details.dx/sku.2395 LEDs it makes possible a good economical light for 55 gallon and smaller tanks. If I had enough room in my budget I would make one just to verify my belief that a 55 gallon tank light for $125 is now possible.


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## CptanPanic

JDowns said:


> First look made me feel as though the tank would have measured less par in comparision to the T5 fixture it replaced (3 x 80w), not triple the par output.


Do you have any pictures of this fixture? Any ideas why your PAR readings are so different than Hoppy's?


----------



## intermediate_noob

Digikey has some good information in their latest online magazine about LEDs that I thought would go good with this post. http://reference.digikey.com/TZ/lighting/2010/WebProject.asp?BookCode=dtz10flx&from=2#


----------



## Hoppy

I am thinking of converting my 65 gallon tank from a riparium to a low light, non-CO2 tank, which started me to thinking about my light for that tank again. While playing around with how much it would cost to make another fixture, it occurred to me that there might be other advantages to LED light fixtures besides what I was aware of. For example, LEDs send a pretty narrow beam of light down into the tank, so LEDs more than 4 to 6 inches away from directly over a spot in the aquarium don't contribute any light to that spot. This should mean that the light intensity near the top of the tank isn't nearly as high as it would be for a T5HO light producing the same PAR at the substrate. After a few hours of calculations, searching my data, etc. then graphing the data a little differently I found that it is true that the distributed lighting from an array of LEDs does not follow the inverse square rule for how the intensity changes, the way a T5 light does. And, if the LEDs stop a couple or three inches from the glass, the amount of light on the glass, which can lead to algae there, is also reduced considerably. Here is a graph summarizing what I came up with - for a 36L x 18W x 24H tank, with LEDs spaced 4 inches apart, in staggered rows:









Notice that if you design for a given PAR at the substrate level, the PAR near the top of the tank is greatly reduced from what a T5 light gives you, and the PAR at the glass is lower than with the T5 light.

I'm not sure if I will go ahead with my plan for that tank, since it would cost me about $160 to make the fixture, but I'm still thinking about it.


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## artemm

Hello Everybody!

Just joined the forum. Before that I annoyed with my question people from reefcentral.com  They were very ammused by question about freshwater plants lighting on a reef forum 

So, I am plannig to migrate to led lights too.
I have pretty much chosen the driver, so this is not a problem.
The problems is with the leds selection.

I think on using Cree XP-G leds and most likely will mix cool and warm to get a better visuals. Probably 60% cools and 40% warms.

I also want to add some deep red 660nm leds from OSRAM to help plant in that spectrum region, becausae crees are not very good at that area.

I went to 
http://ru.mouser.com/ProductDetail/O...7H45NWtQ%3d%3d
and wanted to see the prices and conditions for it. Alas, i could not, because it said that this product is not allowed to be sold in my location by the manufacturer.
So, please, someone, take a look at the link and tell me the price.

I am planning to turn them on for several hours a day.

*Hoppy:*
I have read the whole thready and am glad that you managed to go though all these electrical issues and made it work! Awsome!

Since i was hanging around marine forums and have found tons of DIY LED projects there and some with par data. Look at this one
http://reefcentral.com/forums/showthread.php?t=1587273
The depth is 24", length is 48", the width is unknown, he uses 24 leds (presumable Cree ) XR-E at 700mA w/o any optics and gets PAR around 100 at the bottom. Yours is 20" deep, 30" long and 15" wide and you drive them at 400mA and get PAR 45.
And, lets's what the datasheet says. 
http://www.cree.com/products/pdf/XLampXP-E.pdf
At 350mA it has 100% flux
at 400mA - around 117%
at 700mA - around 180%
So, PAR 45 at 400mA should result in around 70 for 700mA. This is
for 20", for 24" deep it should be even less than 70.

or vice-vsers par 100 at 700mf shoudl result in around PAR 65 for 400mA
And this is for 24", for 20" it should be even more.

What i am saying, that i was expecting par higher that 45 at the bottom of your tank at 400mA. It should've been around 70.

The BIN quality is not problem here, since the curve is true for all bins. I don't get it where you lost the light.


*BTW: *A liitle note on* Apogee quantum meter*. Have you seen the datasheet for it? It is pertty sensitive in yellow area, that's bad. It's sensitivity curve
is pretty far from real plant's PAR curve. But it is okay as long as we compare apples to apples, that is leds to leds, because leds to not change the spectrym much with currenct changes. But comparing T5 and other stuff with LEDS with this meter is..ummm... not very reliable.


Question to *redfishsc*:

What the point of using royal blues in freshwater aquarium? There is plenty of blue in cool white already. Red - that's what is missing.

The unresolved questions are:
1) How many leds i need and at what configuration

I have a pretty much the same tank size (just shorter by a few inches) so i could, of course, use the same config as you do, but i want to hang the lighting at about 30 cm (1 foot) above the tank. So, i will need to use optics at lest for leds near the edges. I am think about 60 degree optics + 40 degree so some places (maybe above light loving plants). BTW: this way you can combine plants with different light requiremnts and play with visual presentation. Anyway, i need to recals everything. What i really need i a par reading from one single LED at several distances in air.
For example: 1 inch away, 1 foot away, 1 meter or 3 feet) away, right at the center of the light stop at some set current.
Starting from there i can do some calculations and see what it will result.
Can anyone give it to me for Cree XP-E or XP-G?
Maybe somone also has optics and can give me an extra set of the same data for led with optics on?

2) Cooling

I really dislikes fans. They make noise and they faul over time and thay can happen anytime, for example, when i am on vacation and light work on auto. So, i'd rather calculate thermals w/o any fans in mind. And after that add a couple low rpm 12-18" fans which will turn on only when temperature is over something. This will be needed for hot summers, though i am not sure about it. If the thermals would be find for the ambient T up to 40C then not fans are needed. 
Anyone known a good tutorial on heatsink calculation?


----------



## chase127

1) LED's - What exactly is your tank size?

2) Fans are pretty much the only way to cool LED's unless you can do some awesome piping job with watercooling like the techy's do on those custom gaming computers 8)


----------



## artemm

chase127 said:


> 1) LED's - What exactly is your tank size?


60cm long x 30 cm wide x 45 cm deep
that's
23" long x 12" wide x 18" deep




chase127 said:


> 2) Fans are pretty much the only way to cool LED's unless you can do some awesome piping job with watercooling like the techy's do on those custom gaming computers 8)


Oh not so true. Depend on the area of the heatsink, thermal resistance, ambient temperature. This all needs to be calculated. 
Let's see, just for laughs, 24 leds at 0.4A with Vf of about 3. That's
0.4x3=1.2W per led, 29W per system. A big heatsink with a lot of fins can easily dissipate that much heat. I had NVIDIA 7700GTS passive cooled
video card wich dissipated around 120W of heat in closed space. Of course, there was air flow in the case and there were 2 heat pipes, the the space was tight and air flow is was not free. So, just a heat sink with nothingh above can feed the ambient air 30W for sure. Have you notice fans in your LED display? 


However, you gave me an idea which i would not do  Pass water to an external filter through the heatsunk to collect the heat. Then it will cool while in the filter and on it's way back and will rise the water temperature a bit, so one can save on the aquarium heater power. Neat, huh?


----------



## Hoppy

Those LED prices are $6.73 for one or $5.61 each for 10, or $5.07 each for 50.

The PAR you get with a LED fixture depends on LED, the current, the distance from the LED, and very important, the distribution of LEDs over the tank. A grid of LEDs spaced 2 inches apart gives a lot more PAR than does a grid of LEDs spaced 4 inches apart. I think that is the reason for the discrepancy you noticed.

Tom Barr compared PAR readings from the Quantum meter to those from a much more expensive meter, the brand of which I forget, and they agreed very well - not perfectly, but very well. So, we consider the Quantum meter to be very adequate for our aquarium lighting needs.

On heat sinks: You can pay your money for an expensive finned aluminum heat sink, and use 800 mA current for the LEDs, or spend the money for more LEDs running at 400 mA, and use cheap aluminum channels for a heat sink. I found that I wanted the larger number of LEDs to avoid the spotlight effect anyway, so I much prefer to use lower current and more LEDs. I just refuse to put a heavy slug of finned aluminum over my tank!


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## artemm

Hoppy said:


> Those LED prices are $6.73 for one or $5.61 each for 10, or $5.07 each for 50.


Thanks!



Hoppy said:


> The PAR you get with a LED fixture depends on LED, the current, the distance from the LED, and very important, the distribution of LEDs over the tank. A grid of LEDs spaced 2 inches apart gives a lot more PAR than does a grid of LEDs spaced 4 inches apart. I think that is the reason for the discrepancy you noticed.


I understand par well. It is a flux density basically  As i understood
you space the leds about 2 inches apart and the other guy does pretty much the same.




Hoppy said:


> Tom Barr compared PAR readings from the Quantum meter to those from a much more expensive meter, the brand of which I forget, and they agreed very well - not perfectly, but very well. So, we consider the Quantum meter to be very adequate for our aquarium lighting needs.


Do you actually mean this article by Dana ?
http://www.advancedaquarist.com/2005/7/review#h11 

Yes, they seem very cloose, the problem with wrong response curve is not Apogee's quantum meter problem only. With their respone you might have a lot of green and yelllow, a bit of red and blue in the spectrum and still get high par reading. For LED with their spectral selectivity it is not a problem but when you start comparing par of leds to par of T5/T8/T12, etc you have a problem. PAR actually is just a very generic term for what plants need. One must look at the spectrum and understand what's their.



Hoppy said:


> On heat sinks: You can pay your money for an expensive finned aluminum heat sink, and use 800 mA current for the LEDs, or spend the money for more LEDs running at 400 mA, and use cheap aluminum channels for a heat sink. I found that I wanted the larger number of LEDs to avoid the spotlight effect anyway, so I much prefer to use lower current and more LEDs. I just refuse to put a heavy slug of finned aluminum over my tank!


Here is the efficiency of XP-G at different currents:
http://www.cree.com/products/pdf/XLampXP-G.pdf
Let's take XPGWHT-L1-0000-00FE4 (neutral white)

at 350mA - 100% of flux, 122lm, Vf=3V, P=1.05W, 116 lm/W, let's count it as 100% eff

at 700mA - around 190% ,232lm, Vf=3.2V, P=2.24W, 104 lm/W , eff 89%

at 1000mA - 250% flux, 305lm, Vf=3.3V, P=3.3W, 92 lm/W, eff 79%

So, at 700mA you get almost 2x lm with a bit more than 2x heat. The difference is not much. The heatsink needed will be pretty much the same for the same amount of lumens.
I am not saying about 1000mA - this becomes clearly inefficient.

But i totally agree with you - more leds and less current is the way to go, if you have the money for more leds 


*Any change on par data from a single led, anyone?
*


----------



## Matt

Thought I'd add my build to this. It wasn't built for growing plants, but more for the looks so take it with a grain of salt (wasn't going for any certain PAR ratings or anything). Just thought it might give someone ideas or inspiration to tweak their own setup. As you can see my heat sink has plenty of room to place more LEDs.

Consists of 2 Cree XRE Cool Whites, and 9 Cree XRE Warm Whites. Cool whites are my moonlights. The splash shield is plexiglass and the heat sink is a 24" x ~8" block of aluminum. Everything is run by hand, no automation here...nice and simple. Rocker switches and dimmers for each bank of lights. All with DC quick disconnects. Works like a charm and runs pretty dang cool. No need for active cooling with a fan, though I did fit some to the heat sink just in case I ever need them. 

I believe the Cool Whites have 80 degree optics on them and the Warm Whites have 60s on them, if I can remember correctly. If you know the basics of + and - and can follow some simple diagrams online/forums its very simple to wire up. I was leaning towards the meanwells but ended up with the buck pucks for their size and I wanted a control box like I have.

















Control box

















Finished product

























Like I said, nothing fancy or anything to grow plants with but its the perfect look I wanted and hopefully can inspire someone else.


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## Hoppy

artemm said:


> I understand par well. It is a flux density basically  As i understood
> you space the leds about 2 inches apart and the other guy does pretty much the same.


Mine are spaced 3 inches apart, which makes a big difference.



> Do you actually mean this article by Dana ?
> http://www.advancedaquarist.com/2005/7/review#h11
> 
> Yes, they seem very close, the problem with wrong response curve is not Apogee's quantum meter problem only. With their respone you might have a lot of green and yellow, a bit of red and blue in the spectrum and still get high par reading. For LED with their spectral selectivity it is not a problem but when you start comparing par of leds to par of T5/T8/T12, etc you have a problem. PAR actually is just a very generic term for what plants need. One must look at the spectrum and understand what's their.


No, Tom posted his comparison on his blog, http://www.barrreport.com/forumdisplay.php/1-Barr-Report as I recall. And, as I understand it, plants use all of the light within the range of the photosynthetic active spectra, so a high PAR is a high PAR, what ever the spectral distribution of the light. Obviously no PAR meter has a flat response curve for the whole range of light it measures, but it is close enough. 


> *Any change on par data from a single led, anyone?
> *


I'm not sure what you are asking here. I do have data on a single one watt LED, but not on a Cree 3 watt one. I am pretty certain the data will be about the same for the higher wattage LED. I use that data to figure out what PAR I can get with various spacings of LEDs.


----------



## Hoppy

Matt said:


> Thought I'd add my build to this. It wasn't built for growing plants, but more for the looks so take it with a grain of salt (wasn't going for any certain PAR ratings or anything). Just thought it might give someone ideas or inspiration to tweak their own setup. As you can see my heat sink has plenty of room to place more LEDs.
> 
> Consists of 2 Cree XRE Cool Whites, and 9 Cree XRE Warm Whites. Cool whites are my moonlights. The splash shield is plexiglass and the heat sink is a 24" x ~8" block of aluminum. Everything is run by hand, no automation here...nice and simple. Rocker switches and dimmers for each bank of lights. All with DC quick disconnects. Works like a charm and runs pretty dang cool. No need for active cooling with a fan, though I did fit some to the heat sink just in case I ever need them.
> 
> I believe the Cool Whites have 80 degree optics on them and the Warm Whites have 60s on them, if I can remember correctly. If you know the basics of + and - and can follow some simple diagrams online/forums its very simple to wire up. I was leaning towards the meanwells but ended up with the buck pucks for their size and I wanted a control box like I have.
> 
> Finished product
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Like I said, nothing fancy or anything to grow plants with but its the perfect look I wanted and hopefully can inspire someone else.


I think those photos demonstrate some stuff about LED lights. First, notice that a lot of the light is wasted on lighting the wall, and too little light is reaching the ends of the tank. This is partly because the light hangs above the tank. With LEDs we can limit the wasted light if we keep the light fixture near the top of the tank, and we can distribute the light uniformly over the tank if we use lots of lower wattage LEDs. This has the added advantage of reducing the difference between the light intensity near the top and near the bottom of the tank, and it reduces the light striking the glass, which should reduce green dust and green spot algae problems. This is why I prefer using only 300-400 mA current with Cree LEDs, instead of 700-800 mA, and why I prefer to get the cheapest bin versions, and use more of them spaced more closely together, better matching the footprint of the tank.

I really like the appearance of your design though. LEDs are so tiny we can make almost any shape fixture, even one that is less than an inch high, using them. I'm not much of an artist, so I have trouble making things that are visually appealing, but you did that very well with this.


----------



## artemm

Hoppy, do you think that narrowing angle at the edge rows of leds will help with algae on the glass even futher?

One more question, i don't fully understand from the pics, how many leds do you have in series on one driver now?


----------



## artemm

Hoppy said:


> Mine are spaced 3 inches apart, which makes a big difference.


I used Cindirella software to build a geometry of the light with 2 and 3 inches apart. Used a depth of 22 inches.
With 3 inches apart the overall intersection on more than 50% light output area is about 73 inches. The hot spots overlap at 7.8 degrees.
With 2 inches the total intersection is 74.2 inches and host spots overal
at 5.2 degees. 
In the first case the second led add to the first one around 95-96% of its insensiti.
In the second case the second led add to the first one around 98-98% of its insensitity.
The third led difference between 2 and 3 inches apart also is around 4-5%. So, overall light intensity with 2 inches apart is not 50% more than with 3 inches. Still, something else is here. That why i need the measurement from one led. 




Hoppy said:


> No, Tom posted his comparison on his blog, http://www.barrreport.com/forumdisplay.php/1-Barr-Report as I recall. And, as I understand it, plants use all of the light within the range of the photosynthetic active spectra, so a high PAR is a high PAR, what ever the spectral distribution of the light. Obviously no PAR meter has a flat response curve for the whole range of light it measures, but it is close enough.


The only post from him about the issure i found on that forum was the link to the Dana's comparison, not his personal.

Here it is:
http://www.barrreport.com/showthrea...iCOR-vs-Apogee?highlight=apogee+quantum+meter

I am afraid you mistunderstood the PAR. Plants (all plants in general) use all PAR range of spectrum, however, the sensitivity and usable range is specific for each plant. There is so called PUR which is actually unmeasurable without multimillion lab equipment and months (if not years) of research for species. But it is already known, that plants can do very well pretty much without any GREEN and YELLOW spectrum. Green is for sure not used because you see the green leaves, so, all the green is reflected back is not used. Yellow is there too, if you split the spectrum you'll see a lot of it. All this is already experimentally confirmed. Guys at ISS grow salad with only blues and red leds and the salad is yami  
So, as you see the sensitivity of plant to PAR spectrum is absolutelly not flat. Blues and reds have a lot more priority than everything else. However, if you look at the apogee quantum meter response curve (can't say anything about LiCor because i did not find their datasheet for the sensor) here http://www.apogee-inst.com/manuals/MQ-100_200_300manual.pdf (page 2).
you will see that sensor has pretty much the same respone in 470-600 nm range (green yellow) comparing to more important blues and reds while the real plant are considerably less sensitive in the range of 470-600. So, as i said, point your par meter at a bright green light and you will get high PAR reading which mean nothing to a real plant. Plant eventually will die under that light. It is also have been shown in experiments.
And just for some extra info (the first thing i found):
http://www.biology-online.org/biology-forum/about16409.html




Hoppy said:


> I'm not sure what you are asking here. I do have data on a single one watt LED, but not on a Cree 3 watt one. I am pretty certain the data will be about the same for the higher wattage LED. I use that data to figure out what PAR I can get with various spacings of LEDs.


Okay. i would appriciate it if you gave me the data. Maybe it will help.

I am basically asking to point a 3W cree led directly to a par meter at any distance and any current and tell me the readings and do the same at some different distance.


----------



## Hoppy

Here are a couple of plots of the data I got from a one watt LED. I have other plots, but most of them I haven't converted to jpg format, and they just rearrange and smooth the data here.


















It isn't true that all of the green spectrum is reflected by plants. It is true that more green is reflected than other colors, so plants use less of the green light available, but they still do use a lot of it. I would have to refer you to Tom Barr for citations on that, because I don't keep that kind of stuff readily available. It is cited in at least one post here on one of these forums. Much of the reason plants look so green to us is that our eyes are very sensitive to green and yellow. To hummingbirds, for example, the leaves don't look green.


----------



## artemm

Hoppy said:


> It isn't true that all of the green spectrum is reflected by plants. It is true that more green is reflected than other colors, so plants use less of the green light available, but they still do use a lot of it. I would have to refer you to Tom Barr for citations on that, because I don't keep that kind of stuff readily available. It is cited in at least one post here on one of these forums. Much of the reason plants look so green to us is that our eyes are very sensitive to green and yellow. To hummingbirds, for example, the leaves don't look green.


Well, yes, Plants use green and yellow too. Simple because making a very selective sensor for a nature has no evolutionary advantage and according to quatum laws there is always some spread. So, yes, they do use the question does they really need it and the answer is: hardly. Try to grow plants under green light only in a dark room. If they don't die small they will a look weak anyway. This all depends on species. Some are very sun loving and die under green and some can use some of it and live unhealthy life. Anyhow, the point was that quantum meters are really not that perfect to reliably compare different sources of lighting and it there sensitivity curve is actually gives more for non-led lighting. So, when measuring halids and FCLs the actual PAR output is worse than it reds. For leds with their spectral selectivity the problem is a lot less.

Interesting reading:
http://www.e-prolab.com/en/conf/papers_pdf/krist.pdf


Thank you very much for the data! Now i have numbers to play with


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## MosMike

artemm said:


> Interesting reading:
> http://www.e-prolab.com/en/conf/papers_pdf/krist.pdf


Good find!



> Students can see what colour of light is the best for
> plants growth and in what conditions the chlorophyll
> content is maximal. Such data are presented in Table 1.
> The experiment shows that the chlorophyll content was
> maximal in plants grown in red and white color lighting,
> and the chlorophyll content was minimal in plants grown
> without light and in IR light. It shows also that IR light
> stops chlorophyll production in plants.


But if we increase the red content we will obtain a warm white light. Not very pleasant for the majority of us.




I have tried using warm white LEDs - they are too yellow. But currently I have good results with Neutral White - nice white color and a higher share of red vs. cool whites.


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## artemm

Yeah, i was thinking about neutrals too. I cannot decide yet what to do. 
With a mix of cool/warm i can do neat tricks like MC controlled mornings and evenings with warm white and then full blown cool white day. Heck know why i would want to do that 
But cool along looks too cool. For looks either cool/warm mix or neutrals.
Don't know about cool/neutrals mix though. Might help, might not.
Other considiration is the amount of blue output. With neutral the total light is the same, but as i see from the graph the power output for blue is reduced by considerably (maybe by 20-30%, look at the area between green and blue lines). I while i want to add separare 660nm reds i don't want to add blues too.


----------



## Wicket_lfe

Based on this chart, is it pretty much useless past 20 inches or so?

sorry for the noobish question.




Hoppy said:


> Here are a couple of plots of the data I got from a one watt LED. I have other plots, but most of them I haven't converted to jpg format, and they just rearrange and smooth the data here.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> It isn't true that all of the green spectrum is reflected by plants. It is true that more green is reflected than other colors, so plants use less of the green light available, but they still do use a lot of it. I would have to refer you to Tom Barr for citations on that, because I don't keep that kind of stuff readily available. It is cited in at least one post here on one of these forums. Much of the reason plants look so green to us is that our eyes are very sensitive to green and yellow. To hummingbirds, for example, the leaves don't look green.


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## artemm

Wicket_lfe said:


> Based on this chart, is it pretty much useless past 20 inches or so?
> 
> sorry for the noobish question.


This is for a lousy 1W led when gives par 80 at 2inch distance. For XP-G 3W this is more like 200-400, maybe. I did not calculate anything yet.


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## Hoppy

One watt LEDs are pretty useful for low tanks, but not tall ones. However, one LED will not give enough light even with 3 watt LEDs. It is by spacing them correctly that you get light from multiple LEDs adding together to get enough light. You could use the 1 watt ones on a 20 inch high tank, if you were to space them about an inch apart. But, that would be very uneconomical.


----------



## paronaram

Hey Hoppy,

Do you knew where on internet I can get U shape aluminum rails? (I am looking for a good price )
I was thinking to make a grid from this rails and mount LED on it.
So this will be big heat sink and mounting chassi 
Most of the LEDs base is 2cm, so if I get something around 1" on the bottom of the U, that will be just perfect.

Have you experiment with this type of LED mounting technique?

Thanks.


----------



## Hoppy

paronaram said:


> Hey Hoppy,
> 
> Do you knew where on internet I can get U shape aluminum rails? (I am looking for a good price )
> I was thinking to make a grid from this rails and mount LED on it.
> So this will be big heat sink and mounting chassi
> Most of the LEDs base is 2cm, so if I get something around 1" on the bottom of the U, that will be just perfect.
> 
> Have you experiment with this type of LED mounting technique?
> 
> Thanks.


Those are aluminum "channels", and yes, I used them for my LED fixture, but probably not the way you intend. For the fixture I am now planning to make I will use 1 7/8 inch wide channels, spaced about 3 1/2 inches apart. And, I will have the open side of the channel facing the water, with the LEDs attached on the inside flat surface.

There is a surplus metals store near me, where I can get aluminum extrusions pretty cheaply - the 1 7/8 inch channels cost $18 for a 13 foot length, on sale now.

There was a post here someplace where someone else used this technique, so I'm copying the idea from him.

Here is a place you can buy aluminum extrusions on the internet http://www.speedymetals.com/pc-2534-8348-12-x-2-x-18-channel-6063-t52-aluminum-extruded.aspx


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## Min

wow guys that is too much calculations involved here. i spend less than this in college. 
if i can help i just did a 8 cree led xp-g light for my 55g. cost me under $90 including soldering tools. some pics here. 
let me know if i ca help. 
http://picasaweb.google.com/mindei/Akvariumas#5553861332553047682


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## paronaram

Min, Looks Good! Nice setup!

Looks brand new setup, it always looks nice and "shiny" :icon_wink

Do you have any pics from 4 month later? With very bright light you may grow a major algae! Make sure you can dim that brightness a little


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## Min

Thanks! the tanks is probably about 3 months old or so, just now got the lights done, since they almost took 1 months to ship from china. 
my plants were struggling much, but seems they like new lights much better. 
i will have to set some hours for the lights, as those are not dimmable. 
IMO i would rather have fewer lights and run them full power then have x2 more lights and run them %50.


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## Hoppy

I built another LED light, described here, http://www.plantedtank.net/forums/diy/123797-diy-led-light-45-gallon-tank.html This uses cheap EBay LEDs.


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## Arctangent

artemm said:


> 60cm long x 30 cm wide x 45 cm deep
> that's
> 23" long x 12" wide x 18" deep
> 
> 
> 
> 
> Oh not so true. Depend on the area of the heatsink, thermal resistance, ambient temperature. This all needs to be calculated.
> Let's see, just for laughs, 24 leds at 0.4A with Vf of about 3. That's
> 0.4x3=1.2W per led, 29W per system. A big heatsink with a lot of fins can easily dissipate that much heat. I had NVIDIA 7700GTS passive cooled
> video card wich dissipated around 120W of heat in closed space. Of course, there was air flow in the case and there were 2 heat pipes, the the space was tight and air flow is was not free. So, just a heat sink with nothingh above can feed the ambient air 30W for sure. Have you notice fans in your LED display?
> 
> 
> However, you gave me an idea which i would not do  Pass water to an external filter through the heatsunk to collect the heat. Then it will cool while in the filter and on it's way back and will rise the water temperature a bit, so one can save on the aquarium heater power. Neat, huh?


Last semester I took my first stab at a formal research paper as a part of my measurements and instrumentation class for mechanical engineering. I ran a thermal torcher test on a cree xp-g (IIRC). Recorded temp from the back of a 20mm star MCPCB (note: No extraneous heat sink) using a DS18B20 sensor and an Arduino. Used some math (from themal resistance, power dissapated, and ambient temps) to convert the MCPCB temp to junction temp. The power dissapated in the LED was controlled and varied with the Arduino via PWM.

At room temp and no airflow I was supprised to find that the junction temp just barely eclipsed the critical maximum recommened value of 150 Celsius at the maximum current of 1A. Meaning that, for all powers tested less than full power, the LED would not overheat. Yes it would get very hot which presents its own issues, but not to the point of damaging the junction. I did record junction temperatures greater than the maximum allowable duing the full 1 Amp test, but just barely, possibely within the resolution of my equipment at that temp. I bought 4 LEDs thinking I would need to burn at least one out to find the failure power (with no heatsink), but I was infact unable to destroy even one LED.

Comments: 
A heat sink should be thought of as a way to keep the _casing_ temperature down (so you won't burn yourself or your house).

In the discussion above the LED had acess to a constant temperature thermal reservoir (air in the room). However if it were enclosed, the ambient temperature may increase by 20 degrees causing a corrosponding increase in the junction temperature of 20 degrees.

Just thought I would share.


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## [email protected]

I love it when a skilled researcher posts useful information. Thank You!

I use the wayback machine to pull old threads from the days when grad students were the only ones who had access to UseNet areas. There is a lot of solid research behind many of today's "taken for granted" small miracles.


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## Delgriffth

im all for diy and im not trying to burst anyones bubble but a light fixture is something probably not worth the risk IMHO. if something did go wrong and there were damages to your home etc good luck trying to collect from your home owners insurance without a ul listing on your fixture. im a master electrician and could build any diy light from parts around the shop but the savings from a diy isnt worth the risk you take again. you can do everything right, perfect craftmanship etc but say the driver is faulty from the manufacture through no fault of your own and causes damages. ive seen t5 ballasts literally explode and blow themselves apart. again, im not lecturing anyone and most of the diy lights ive seen are well built. but there is a risk.


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## Hoppy

Delgriffth said:


> im all for diy and im not trying to burst anyones bubble but a light fixture is something probably not worth the risk IMHO. if something did go wrong and there were damages to your home etc good luck trying to collect from your home owners insurance without a ul listing on your fixture. im a master electrician and could build any diy light from parts around the shop but the savings from a diy isnt worth the risk you take again. you can do everything right, perfect craftmanship etc but say the driver is faulty from the manufacture through no fault of your own and causes damages. ive seen t5 ballasts literally explode and blow themselves apart. again, im not lecturing anyone and most of the diy lights ive seen are well built. but there is a risk.


I crawled out of bed this morning - almost stubbed a toe, could have fallen and hit my head. :tongue:


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## original kuhli

I think you're in the wrong forum.



Delgriffth said:


> im all for diy and im not trying to burst anyones bubble but a light fixture is something probably not worth the risk IMHO. if something did go wrong and there were damages to your home etc good luck trying to collect from your home owners insurance without a ul listing on your fixture. im a master electrician and could build any diy light from parts around the shop but the savings from a diy isnt worth the risk you take again. you can do everything right, perfect craftmanship etc but say the driver is faulty from the manufacture through no fault of your own and causes damages. ive seen t5 ballasts literally explode and blow themselves apart. again, im not lecturing anyone and most of the diy lights ive seen are well built. but there is a risk.


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## Delgriffth

haha..nah im in the right forum and my opinion is just as welcome as yours. ive read how hoppy built his light and it looks fine to me. probably built better then anything you could buy off the shelf. but as someone who repairs lights daily ive seen what happens when they fail. now anything can fail at anytime as hoppy implied in his post and i know that. if your diy stand collapses youll have a big mess. if your diy co2 fails youll have dead fish or an algae bloom. but if your diy light fails your f'ed. good luck.


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## Min

Arctangent said:


> Last semester I took my first stab at a formal research paper as a part of my measurements and instrumentation class for mechanical engineering. I ran a thermal torcher test on a cree xp-g (IIRC). Recorded temp from the back of a 20mm star MCPCB (note: No extraneous heat sink) using a DS18B20 sensor and an Arduino. Used some math (from themal resistance, power dissapated, and ambient temps) to convert the MCPCB temp to junction temp. The power dissapated in the LED was controlled and varied with the Arduino via PWM.
> 
> At room temp and no airflow I was supprised to find that the junction temp just barely eclipsed the critical maximum recommened value of 150 Celsius at the maximum current of 1A. Meaning that, for all powers tested less than full power, the LED would not overheat. Yes it would get very hot which presents its own issues, but not to the point of damaging the junction. I did record junction temperatures greater than the maximum allowable duing the full 1 Amp test, but just barely, possibely within the resolution of my equipment at that temp. I bought 4 LEDs thinking I would need to burn at least one out to find the failure power (with no heatsink), but I was infact unable to destroy even one LED.
> 
> Comments:
> A heat sink should be thought of as a way to keep the _casing_ temperature down (so you won't burn yourself or your house).
> 
> In the discussion above the LED had acess to a constant temperature thermal reservoir (air in the room). However if it were enclosed, the ambient temperature may increase by 20 degrees causing a corrosponding increase in the junction temperature of 20 degrees.
> 
> Just thought I would share.


i love this! all this time i was truly thinking this way, but could not find any proof. the heatsinks are over rated just for company profits. i never heard of LED burn out due to overheating. 

as a renegade example my DYI led lights running full power at 1050ma for about 3 months now on 36" by 1 1/2" aluminum strip and its ok.


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## Min

Delgriffth said:


> haha..nah im in the right forum and my opinion is just as welcome as yours. ive read how hoppy built his light and it looks fine to me. probably built better then anything you could buy off the shelf. but as someone who repairs lights daily ive seen what happens when they fail. now anything can fail at anytime as hoppy implied in his post and i know that. if your diy stand collapses youll have a big mess. if your diy co2 fails youll have dead fish or an algae bloom. but if your diy light fails your f'ed. good luck.


your co2 tank can fall on your toe and brake it or your valve can brake off and it will rocket out the window. 

if you know enough about electrics, the power conversion to LED current would be the effect of throwing batteries in your tank. even the fish would survive.


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## cggorman

I know that Cree XR and XP series diodes are far and away the most popular emitters in the hobby, but I feel they have less than ideal spectral distribution. For my project, I decided to use LedEngin LZ1 neutral white for my main source. Unfortunately, even those have a big shortfall in CRI compared to the flourescent sources I am replacing. To supplement the white LEDs and hopefully correct the CRI up to something more acceptable, I added Lexeon Rebel 505nm (cyan). A careful comparison to natural daylight also shows a slight defficiency in the far red end of the spectrum so I also added LedEngin reds in both 660nm and 735nm. The 735 is sketchy, but I wanted to try it. The 660s are at a photosynthetic response spike and also help show off the red in my fish. 

You may wonder about the ultraviolet end of the spectrum...After testing with three or four different colors from 400nm down to about 320nm, I found the fish turned black (no flourescence), floating particulates in the water flouresced unaesthetically (turning the water milky in appearance), and read several articles indicating that UV was at best marginally beneficial (if not detrimental) to the health of both the fish and the plants...so I elected to leave that piece of the spectrum out. (not to mention the emitters are expensive)


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## Naekuh

can someone tell me about how 660nm led's work in fresh water fish tanks? 

Are they good but make things look funny? or they asking for an algae bloom on biblical levels? 

Wondering if 660nm LED's should be considered as cree makes them in 3W sizes too.


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## silvawispa

I have no direct experience with the 660nm lights, but maybe I can point you at some info.

I've been reading some studies on the effects of light frequencies on aquatic plant growth and come across some interesting results.
Sadly I haven't saved my sources, but google is your friend too!

All studies I looked at were done with freshwater aquatic plants typically found in an aquarium. I think that is quite important!

One study I looked at concluded that red light was implicated in creating compact branched growth, green light(as might be found in a deeper lake) gave leggy growth(long internodes, lower chlorophyll) with white light and blue light giving a more 'normal' growth. 

The upshot for me, is that my next LED purchase will be a combination of warm white, that has a good dollop of the 600-700nm wavelengths, whilst not being exactly short of blue light either, and the midrange white LEDs so I don't end up with a 'yellow' tank. These should compliment my cold 'daylight' whites and provide well for the plants.
Time will tell.

If I had gone the 'many small sources' route, I would consider mixing in some reds to encourage the compact growth, but I've seen some messy shadows from that sort of set-up so I'd be thinking hard about the design. I didn't, I've gone for few lights, but powerful.
My feeling is that the white LEDs now available have a suitable enough spectrum coverage for a good looking, strongly lit, healthily growing planted aquarium.

The main focus of my reading was how plants adapt to different wavelengths as they become available, for example as water depth changes or the plant grows.
It seems that some plants do adapt to different light frequencies and some don't...


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## prototyp3

Quick question for you folks running LEDs.. How much far do LEDs with optics stick out from the surface they're mounted to? I'm trying to figure out how much clearance I need for the enclosure.


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## silvawispa

I just can't resist, no offence meant!

http://lmgtfy.com/?q=led+60º+optics+data+sheet

The answer is there.


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## prototyp3

silvawispa said:


> I just can't resist, no offence meant!
> 
> http://lmgtfy.com/?q=led+60º+optics+data+sheet
> 
> The answer is there.


Yeah, because we all know there is only one LED type and optics used in the hobby..


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## Dragonfish

Typically about 5/8".


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## prototyp3

Thanks for that. 

Anyone have any experience or thoughts on this LDD-H series driver from Mean Well?
http://www.meanwell.com/search/ldd-h/LDD-H-spec.pdf

I'm looking at building a couple lights that will have 4 different channels of LEDs independently controlled. Each channel would have 4-12 LEDs. I would be using an Arduino board to control these channels via PWM. Any red flags in this spec sheet that I'm overlooking?


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## tentacles

Not related to the previous post, but I just had a look at the Cree XPG lifespan documents (they have so far actually completed over 10000 hours of actual testing), and the XPG series holds up quite a lot better than previous ones.. At 55C case and 55C ambient (ambient is actually very important to lifespan), at 1A current at 6000h the LED still produced 100% of output. The L70 life (down to 70% brightness) at 85C/85C/1A is estimated at over 60000 hours. 

I don't know about you guys, but I expect that I'll replace my emitters in under 5 years - think about it, in 5 years there will be some REALLY amazing stuff on the market, probably with spectra specifically designed to make plants grow like algae and the colors of our fish melt our eyes. 

See http://www.cree.com/products/pdf/LM-80_Results.pdf page 14


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## Chlorophile

How many / what kind of LED's would be good for a low light 20G High.

I like the idea of having some of that nice ripple effect, but at the same time I don't want stems all growing towards the middle or something. 

Would 6 XM-L's on a 10"x10" heatsink work? I'd probably under drive them around 400mA. 
Seems like it might be too bright.
It'd have to be passively cooled too I can't stomach the idea of a fan.


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## Hoppy

A 20 gallon high tank is roughly 24L x 12D x 16H. I don't think a 10" x 10" heatsink would be good for that. Much better would be a 18-20" long heatsink which could be as narrow as 2-3 inches. A piece of extruded aluminum channel would work fine, since you intend to use it at low current.

Using 6 Cree XM-L evenly spaced along that heatsink, say 3 inches apart, running at 400 mAmps should give you about 40 micromols of PAR at the substrate, with the light sitting on top of the tank, with no optics. Raise it about 6 inches and you should get about 30 micromols of PAR, good low light. If you zig-zag the LEDs across the top of the tank so you effectively have two rows, with them spaced about 3.5 inches apart on diagonals - two rows 1.5 inches apart - you should get about 3/4 of that PAR, so you could sit the light right on top of the tank for low light. Then the plants wouldn't grow to the middle quite as much, and the PAR from front to back of the substrate would be more uniform.


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## justdaman

hey guys! just want to know if this kind of led fixture can properly light up a 2ft tall tank. i was thinking of putting 8 of these along a 6x2x2ft tank

its a 10 watt led flood light fixture









specs are here
http://www.newsunshine.net/10W-flood-light-LED-Underwater-Lamp-82.html

they also have higher wattage bulbs 20watt up.

thanks in advance!


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## Kanne26

Wow this whole thread is intense and way over my head (I started on the PAR vs Distance thread to attempt to learn how much PAR my LED strip is giving out).... I still have no idea. Can someone help me? I currently have a 20gal high with one of these sitting on top of it: http://www.aquariumplants.com/Lumen..._accurate_LED_for_fre_p/lb02.htm?1=1&CartID=0. I keep hearing that LEDs aren't strong enough to grow plants, but others have told me this is super high lighting... so I'm gettin' a bit confused! I don't wanna over or undercook my plants. I'd like my PAR to be around 30-40.....


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## Hoppy

You really have to use a PAR meter to find out how much light you get for that fixture. I notice it can be dimmed, and I suspect you will have to dim it to avoid having too much light for a planted tank. 

I'm getting very close to a good design for a conversion of a cheap lux meter to a waterproof PAR meter, so if you want to be on the list for possibly buying one, PM me and I will add your name to my list. It would be way cheaper than buying a commercial PAR meter.


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## AquaDwell

EDIT: After reading the LED FAQ, my questions have been answered.


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