# A DIY LED light for a 45 Gallon Tank



## [email protected] (Jul 17, 2008)

Hoppy, you document things between pretty well to excellently. 
If you'd post or PM your PayPal address, I believe some of us would help defray the cost of construction in exchange for every tiny detail of the project. Because we know you're going to make it work. 

I'll commit to $10.00. 
It will be worth that to avoid re-reading the LED thread again. ;-) 

I've read a lot of posts on LED builds but they always omit or seem to omit something. I've not been able to "get" the whole picture. For instance, some talk about drivers, but omit details on weather there is a need for a power supply or if it's a direct 120 V AC to the driver. I had to read a spec sheet to find out Brown on the driver connects to Black, and Blue on the driver connects to White. Sheesh!

One example of what I don't get:
On your post above you mention the MeanWell ELN 60-48 driver and 36 LEDs, but the spec sheet says it can power only 8 to 14 LEDs. ??

Thanks.


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## Hoppy (Dec 24, 2005)

[email protected] said:


> Hoppy, you document things between pretty well to excellently.
> If you'd post or PM your PayPal address, I believe some of us would help defray the cost of construction in exchange for every tiny detail of the project. Because we know you're going to make it work.
> 
> I'll commit to $10.00.
> ...


Who is this "Meanwell fellow" who is trying to tell me how to use his product?

That MeanWell driver provides up to 48 volts, at a constant current adjustable between zero and 1.3 amps. 48 volts means it will provide enough oomph for 48/voltage drop of one LED LED's, or for this particular LED, for 48/3.2 to 3.5, or 13 to 15 LEDs in series, providing 1.3 amps through all of them. But, I don't want to drive them at that current. Instead I will drive them at 1/3 of that current or 433 mAmps. To do that I will use three series strings of 12 LEDs in parallel. Wattage will be about 12 x 3.5 x .433 = 18 watts. The rated power for that driver is 62.5 watts. So, if this doesn't work, I'll sue them!

The hardest thing to explain is how I came up with an array of 36 LEDs in 4 rows of 9 LEDs, spaced 3.5 inches apart each way. When I get nice and calm and clear headed, I will try to do that.

P.S. You can't buy me for $10 :icon_cool Now, go read the sticky again.


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## Hoppy (Dec 24, 2005)

Here is how I decide how many LEDs at what spacing will give me the PAR I want:

About 6 months ago I bought a few cheap 1 watt LEDs on Ebay, with individual drivers for each one. I reported on that http://www.plantedtank.net/forums/lighting/108678-cheap-led-light.html

Using the PAR data I got I made some graphs:








This one showed how much PAR one LED would give on an off center spot below the LED, at various distances from the LED.

Plotting that data differently gave this:









Since this was for a cheap 1 watt LED, I extrapolated to what a Cree XR-E would give at 425 mAmp. This, from the Cree specifications:









This was the extrapolated plot for the Cree LEDs









I refined it a bit to get this: (As I recall, I calculated what my existing LED light should give, and adjusted the graph until it agreed.)









Continued:


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## Hoppy (Dec 24, 2005)

If you use an array of LEDs spaced a given distance apart, both ways, you get nearly uniform PAR over most of the substrate. Such an array would be:









You can see that at a spot under one LED, there are others offset a few inches that can also contribute some PAR. So, you need to determine the PAR contribution for each LED, close enough to contribute any, and add them up for that spot. For example if the LEDs are spaced 3.5 inches apart, 4 LEDs will be offset by 3.5 inches, 4 at 4.9 inches, 4 at 7 inches, 8 at 7.7 inches, etc. The PAR contributions from the ones farther away is small, but with 4 or 8 of them added up, they are significant.

When I did this for the 3.5 inches spacing I got a total of about 50 micromols of PAR. So, I tried it with the rows staggered, and that reduced the PAR down to about 40 micromols. That was about what I want, so I chose 3.5 inches for my spacing.

I have other graphs I use to make this is a little easier, but that's the process.

The array I selected is:


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## Hoppy (Dec 24, 2005)

This is the housing/heatsink, not assembled yet, without the holes and notches cut yet. Cutting 1/16" thick aluminum extrusions is extremely easy with a hacksaw. After cutting pieces that are to be the same length, just clamp them together with the ends on one end aligned, then file the other end to even them up.


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## [email protected] (Jul 17, 2008)

Hoppy said:


> Who is this "Meanwell fellow" who is trying to tell me how to use his product?
> 
> That MeanWell driver provides up to 48 volts, at a constant current adjustable between zero and 1.3 amps. 48 volts means it will provide enough oomph for 48/voltage drop of one LED LED's, or for this particular LED, for 48/3.2 to 3.5, or 13 to 15 LEDs in series, providing 1.3 amps through all of them. But, I don't want to drive them at that current. Instead I will drive them at 1/3 of that current or 433 mAmps. To do that I will use three series strings of 12 LEDs in parallel. Wattage will be about 12 x 3.5 x .433 = 18 watts. The rated power for that driver is 62.5 watts. So, if this doesn't work, I'll sue them!


I believe it might finally be coming together in my head now. 
Am I correct that you are going to use three parallel strings, with each string consisting of twelve LEDs in series?



> The hardest thing to explain is how I came up with an array of 36 LEDs in 4 rows of 9 LEDs, spaced 3.5 inches apart each way. When I get nice and calm and clear headed, I will try to do that.
> P.S. You can't buy me for $10 :icon_cool Now, go read the sticky again.


I was actually hoping fifteen of us could buy you a light. 
<sigh> I'll re-read the sticky this weekend. It's gotten to be too much for an evening. Maybe if I take notes this time. 
I did skip ahead on this thread. It's looking good. Thanks. 

A tip for the lazier ones among us. Wrap the aluminum in masking tape to hold your line all the way around the piece and use a jig or sabre saw with a metal cutting blade. Yeah, I'm one of those guys who manages to twist a hack saw blade on every cut. I'm looking at a cast iron one with Vise Grip blade supports for my next one. The UFO grade metal isn't heavy enough for me.


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## Hoppy (Dec 24, 2005)

[email protected] said:


> I believe it might finally be coming together in my head now.
> Am I correct that you are going to use three parallel strings, with each string consisting of twelve LEDs in series?


Yes, that's correct. Oddly enough the manufacturer recommends that the LEDs be interconnected across the strings, like a net with an LED at each crossing of wires. That guarantees that each one gets the same current, but I can't see wasting all of that extra wire.


> I was actually hoping fifteen of us could buy you a light.
> <sigh> I'll re-read the sticky this weekend. It's gotten to be too much for an evening. Maybe if I take notes this time.
> I did skip ahead on this thread. It's looking good. Thanks.


That would certainly be nice, but I doubt that there are 15 who would contribute. But, I have a pair of 2 foot lengths of Aluminum channel left, and enough aluminum angle to tie them together, so I could set that up for a light for a 10 gallon tank very easily, if anyone was interested.


> A tip for the lazier ones among us. Wrap the aluminum in masking tape to hold your line all the way around the piece and use a jig or sabre saw with a metal cutting blade. Yeah, I'm one of those guys who manages to twist a hack saw blade on every cut. I'm looking at a cast iron one with Vise Grip blade supports for my next one. The UFO grade metal isn't heavy enough for me.


I have a reciprocating "demolition saw" that I use when cutting thicker pieces or pieces of steel. But, it is too hard to control for thin aluminum.


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## Hoppy (Dec 24, 2005)

The wire passage holes are now drilled in the aluminum channels. The wires to the LEDs need to be hidden from view, so they will all run under the aluminum. It is necessary to drill them before assembling the housing/heatsink because you can't get to the sides of the channels to drill holes once it is assembled.


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## Hoppy (Dec 24, 2005)

I ordered 40 LEDs on Ebay, for about $75, and they were shipped a couple of hours after I ordered them! But, then I ordered the Meanwell LED driver, from the cheapest online store, then got a message that it would be shipped in April of this year! I am trying to cancel the order, but everyone at that site is on New Year's vacation, so that has to wait until Monday.

While waiting, I am going to modify this support bracket so it will work with the new light:









I need to change the method of attaching to the light. First step is to take two Tee fittings and stuff the through passage with plumbers epoxy.









I will cut off half of those ends, to leave me with something to convert to attachment fittings.


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## Cuchulainn (Nov 2, 2010)

Sweet we finally get to see your articulated support bracket in all its glory!
Have any examples of the "blind" rivets you used Hoppy?I can't see them 

I have a reciprocating "demolition saw" that I use when cutting thicker pieces or pieces of steel. But, it is too hard to control for thin aluminum. Quote~

Nevermind the toxic smoke cloud that arises from cutting aluminum with a rip saw, or zip cut ;(


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## Hoppy (Dec 24, 2005)

Cuchulainn said:


> Nevermind the toxic smoke cloud that arises from cutting aluminum with a rip saw, or zip cut ;(


What is toxic about aluminum and aluminum oxide? I haven't heard this before. It can be dangerous because aluminum in fine particle form can burn pretty easily, and very hot. But, I have used my miter saw, with carbide blade to cut aluminum channels and other thick aluminum extrusions before, with no problems.


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## Hoppy (Dec 24, 2005)

These will bolt on to the back of the light housing, and attach it to the support assembly. The electric power wire will thread out the hole in the center of one of them, through the hollow fittings the support is made of, down one of the pipes which will fasten to the wall and be hidden completely.

The reason for the epoxy in the middle is to prevent tightening the bolts from spreading the cut sides of the tee, which would creep under the load, causing the connection to the light to be loose fairly quickly. This way the crushing load is carried by the epoxy.


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## jeremyblevins (Aug 14, 2010)

very simple and creative i like it.


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## bnbfishin (Dec 23, 2010)

Just get a Milwaukee Band saw and you can cut about anything and it'll work wonders on that thin aluminum


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## Hoppy (Dec 24, 2005)

Progress! First, I struggled with the support bracket for a few days, but now have the electric power lead strung through the bracket, and the bracket drilled to install on the light housing, which isn't assembled yet.

I ordered the Meanwell LED driver from a different vendor last night. It is supposed to be delivered today! Apparently their warehouse is here in Sacramento - Jameco Electronics. Still no response from the other company, but with an April delivery date they certainly have time to cancel the order. I did have to pay about $10 more for the driver, $42, but it's worth it to actually get it.

And, I bought a Pop Riveter to use to assemble the housing/heatsink. Simple device, but I haven't used one for about 40 years.


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## Hoppy (Dec 24, 2005)

The mounting holes and holes for the wires to go below the top of the housing are now drilled and deburred. This is the Meanwell ELN 60-48 LED driver, 48 volts, 1.3 constant amps (adjustable) and 60 watts maximum.

Now, finally, it is time to assemble the housing/heatsink.


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## Hoppy (Dec 24, 2005)

The housing/heatsink is now assembled, with POP rivets (blind rivets). With rivets, the strength of the joint depends on the number of rivets per joint more than on the strength of one rivet, so you can use pretty small rivets, if you use several of them. I used 1/8 inch diameter rivets and 3 per joint. First I center punched the hole locations for one joint, using a small square to make sure the pieces are perfectly square.:









Next, three 1/8 inch diameter holes were drilled through both pieces to be sure they would line up perfectly.









Then 3 rivets were pushed through the holes, again to keep the pieces lined up and square:









Using the simple rivet setting tool all three rivets were set, snapping off the steel rod that pulls the blind end to set it:









This was repeated for every joint, 8 places in all, resulting in a sturdy aluminum open heatsink/housing:









Only one problem occurred: 4 of the rivets had the steel rod snap off leaving a half inch stub behind, instead of snapping off within the rivet body. I used a pair of wire cutters to cut off that stub and a file to file it down flush with the top of the rivet head. I'm sure this means I was not using the exact correct technique, but this works fine anyway.

I think the next step will be using fine emery paper on a wood block to flatten the surfaces the LEDs will mount on.

My total cost is about $140 plus maybe $5 for miscellaneous stuff, like screws and rivets.


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## VaultBoy (Nov 11, 2010)

looking good hoppy keep up the good work im following closely!

and patiently waiting for my ebay LED's to show up so i can join the LED Legion


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## Gibby (Sep 23, 2010)

Out of interest, could you provide the dimensions of the tank Hoppy?


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## Hoppy (Dec 24, 2005)

The tank is 35" X 14+" X 18", with a slightly bowed front, and one piece front and sides. Today I spray painted it glossy white:



















Now, the really exciting part - watching paint dry, at 55F temperature.


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## r3tic (Jan 4, 2011)

Are you mounting the leds to the paint, or is the other side bare? The paint will slightly reduce the ability of the aluminum to dissipate heat into the air. Love the mounting bracket.


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## tzen (Dec 31, 2008)

Very nice!
I, too, just ordered some LEDs and a driver. My wife says I cannot start building until the bathroom remodel is done, so it'll be a couple weeks before I start...


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## Hoppy (Dec 24, 2005)

tzen said:


> Very nice!
> I, too, just ordered some LEDs and a driver. My wife says I cannot start building until the bathroom remodel is done, so it'll be a couple weeks before I start...


I just started working on this on the sly, until, finally today my wife asked what I was doing. Of course it is too late to stop now!:wink:



r3tic said:


> Are you mounting the leds to the paint, or is the other side bare? The paint will slightly reduce the ability of the aluminum to dissipate heat into the air. Love the mounting bracket.


The LEDs go inside the channels, which are not painted, but polished little, so the painted, flat sides are up. From what I read, any paint will greatly improve the radiant heat transfer from an aluminum heatsink, with flat black being slightly better than glossy white. But, the paint layer is too thin to have much effect on convective heat transfer, although it will reduce it a little. And, most of the heat transfer will be convective if the heatsink runs as cool as it should. I'm hoping free convection will be enough since there is no place for a fan. This is intended to be a minimalist design.:biggrin:


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## scapegoat (Jun 3, 2010)

hey Hoppy, wondering if you saw this; http://led.linear1.org/led.wiz and how well it matches to your numbers.

being a tech guy myself, i'm toying with some leds for my tank, perhaps just for "moon light" at this time. but the cool factor of building my own set of LED lights might win me over.

also, the driver. are you merely connecting that to a plug that will go in an outlet? that certainly appears to be the case with this driver. it also appears you won't need any resistors, is that true? if so... this appears to be a very simple DIY project! buy the driver, buy the led's and get soldering!


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## Hoppy (Dec 24, 2005)

scapegoatw said:


> hey Hoppy, wondering if you saw this; http://led.linear1.org/led.wiz and how well it matches to your numbers.
> 
> being a tech guy myself, i'm toying with some leds for my tank, perhaps just for "moon light" at this time. but the cool factor of building my own set of LED lights might win me over.
> 
> also, the driver. are you merely connecting that to a plug that will go in an outlet? that certainly appears to be the case with this driver. it also appears you won't need any resistors, is that true? if so... this appears to be a very simple DIY project! buy the driver, buy the led's and get soldering!


That calculator just tells you what series/parallel circuit you can use, but that's easy to figure out anyway.

It is as easy as you said - Meanwell drivers provide constant current at a fixed voltage, which is all you need for LEDs. They plug into a 120 volt AC circuit (actually a range of voltages) and the output is connected to the LEDs. They don't tell you to do so, but it is a good idea to ground the negative DC lead and the heatsink. This keeps the maximum voltage on the positive side to the number of LEDs in series times the voltage drop per LED, and it keeps the aluminum heatsink at zero voltage above ground for safety purposes.

I just received my package of LEDs, 10 minutes ago, about 2 weeks after I ordered them. You can't beat that for a shipment from China.

I'm not rushed for time, so my next step will be to do some PAR testing of one of each color LED, to verify that my array of LEDs will give the PAR that I want. It's a lot easier to reposition them before I start than after I get them attached to the heatsink and all soldered up.

I will attach one LED to a 2 foot piece of the same aluminum 2 inch channel I'm using for my heatsink, prop it up at varying distances from the desk, use a "target" with circles marked off every inch, and measure the PAR at each radius for several LED to PAR sensor distances. That tells me how big the spot of light will be at various distances, and what the PAR will be at various distances from the center. To power the one LED I have a 5.1 volt DC supply from some computer apparatus I have long since discarded. With 4 15 watt resistors in parallel, to get 3.75 ohms, in series with the LED I should be driving it at about the 430 mA I want.

The next stage of fun begins!


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## Hoppy (Dec 24, 2005)

Nothing seems to ever be simple! In order to test individual LEDs I'm using some 15 ohm resistors to set the current. I will use 2 in parallel to get 7.5 ohms, 3 in parallel to get 5 ohms, 4 in parallel to get 3.75 ohms, and 5 in parallel to get 3 ohms. These paralleled resistors will be in series with the LED, powered at 5.1 volts. But, in order to figure how much current I will be testing them at, and I have to do that, not having a mAmmeter of sufficient range to use, I need to know the forward voltage drop across the LED at various currents. The vendor says that is 3.2 to 3.6 volts. That isn't good enough.

I have a graph of the forward voltage drop on Cree 3 watt LEDs, and the technology is comparable, I assume, so I'm going to use that. Cree's have about 3.2 to 3.6 volts drop in the range of current of interest. So, based on that, and some iteration, I expect to test them at 250 mA, 360 mA, 470 mA and 570 mA. This should let me interpolate my results to the 430 mA I expect to run the light at. Ultimately, I plan to adjust the current to get the PAR I want, but first I have to get more than I want at the 430 mA. I have my test set up pretty well together now, so in the next couple of days I should have some data.


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## Hoppy (Dec 24, 2005)

It's together and ready to start attaching LEDs. And, a grounded power cord still has to be spliced to the power cable coming out of the support bracket. Plus, of course soldering all of the leads to the LEDs. Another week or two of work?


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## MosMike (Dec 4, 2010)

Better hide the licence plate 
Also, black heatsinks dissipate heat better


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## Wasserpest (Jun 12, 2003)

MosMike said:


> Better hide the licence plate


Why? Anyone can drive by Hoppy's house and get it?

That looks great Hoppy. Just make the driver invisible somehow. I like the adjustment mechanism. I might do something like this with a bunch of 5050 LEDs.


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## Hoppy (Dec 24, 2005)

Garages sometimes reveal license plates:icon_lol:

Black heatsinks radiate heat better, but for convection, which will be the primary heat transfer mechanism, a thin layer of paint has little effect, no matter what color it is.

Here is the raw data from testing a "White" LED, one out of the 20 I have.










The most striking thing I see is that this one has a very large area of nearly uniform PAR, much more than the 1 watt one I tested before. The PAR meter doesn't indicate in decimals, so a 2 mms PAR reading really means it is from about 1.5 to 2.5 mms.


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## Hoppy (Dec 24, 2005)

Some more graphs of the data, with another data point added:
First, the PAR at various distances from the LED vs radius out from the point under the LED:









The PAR at various distances from the LED, directly under it, for different LED currents.









Then, interpolating the data above to get the PAR of a single LED directly under the LED, at various LED Currents, at a distance of 18 inches, where I want to use my light.









Finally, "normalizing" the data for PAR off center, by dividing each data point by the PAR at the center, and interpolating for values at 18 inches from the LED.









With the last two charts you can calculate the PAR at any point under an array of these LEDs for any LED current. My array of 36 LEDs spaced 3.5 inches apart both ways, 4 rows of 9 LEDs, should give me about 38 mms of PAR at 18 inches. (However, this is assuming the warm white ones produce the same PAR as these white ones.)

All of this is for the white LED. Tomorrow I will get some data on the warm white one.


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## rhinotam0405 (Mar 15, 2010)

So put me on the list when you start manufacturing them  i need one for a 150 - 
Looks awesome!


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## Hoppy (Dec 24, 2005)

The warm white LEDs are a bit disappointing. They produce less PAR than the white ones. The PAR meter reading at 20 inch distance, 570 mAmps of current, is 2 mms ve 3 with the white ones. This is misleading because the meter isn't that accurate at such a low reading. Both actual PAR amounts could be 2.5, or there could be as much as a 2 mms difference. Using the numbers I recorded with the PAR meter, and a lot of interpolating, etc. I come up with about 30 mms for the light fixture, low compared to the 40 that I want. So, I've increased the number of LEDs from 36 to 39, and reduced the spacing from 3.5 to 3.25 inches. This could increase the PAR by about 10%. The proof will be in actually measuring the PAR from the fixture when it is done.

One bit of very good news: even at 570 mAmps, the piece of aluminum channel, 2" x 1" x 1/16" doesn't get warm enough to even feel. So, the heatsink will be more than adequate.

The warm white LEDs produce a much more yellow light than the white ones. The mix of 20 white and 19 warm white should look pretty good, I think, and the light will be well mixed so no actual different colors of light will be visible.



rhinotam0405 said:


> So put me on the list when you start manufacturing them  i need one for a 150 -
> Looks awesome!


The total parts cost, with the wiring and adhesive for the LEDs will be closer to $160 than $150, and I won't be making these for sale - too much work! I might consider putting a kit together, but I haven't decided for sure.


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## E.Eliveld (Jun 19, 2010)

Hello Sir,

Do you consider RGB leds? And if so why you'r not experimenting with those?

Greetings

Erwin


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## Hoppy (Dec 24, 2005)

E.Eliveld said:


> Hello Sir,
> 
> Do you consider RGB leds? And if so why you'r not experimenting with those?
> 
> ...


I'm trying to do this at a minimum cost, with maximum chance for success. RGB LEDs would cost much more, and my chances for success would be much lower. Also, I don't see any advantage to them over regular white, perhaps with warm white mixed in. I'm doing this mix mostly because I know it will work, but I want to see how much better or worse it looks than just white.


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## Hoppy (Dec 24, 2005)

The heatsink/housing marked to start attaching LEDs using a silicone based thermal adhesive from Radio Shack, which should be plenty good enough considering the low currents I will be running, and only $2 per tube.










About half of the LEDs attached.


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## Hoppy (Dec 24, 2005)

The good news is that aquarium sealant does a good job as a wiring "clamp". The bad news is that Radio Shack's silicone based thermal adhesive isn't an adhesive, just a very viscous grease. I have all of the LEDs attached with that stuff, so I can't remove it and use something else, and the stuff isn't going to hold the LEDs in place forever. Combining the good and the bad news, I am going to use a couple of spots of aquarium sealant to hold each LED, leaving the Radio Shack stuff to act as a thermal paste. I haven't tried it yet, but I'm sure it will work.

I've started soldering the wiring on, but only have 5 of the 39 wired so far. That, at least, is working well.


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## tzen (Dec 31, 2008)

It sounds like the critical aspect is to try to fill the small air gap between the stars and aluminum with anything that has higher thermal conductivitiy than air, and use as little as possible, so that the aluminum parts can be as close together as possible.
I have seen citations that said Desitin, a zinc-oxide in petrolatum ointment that is used for diaper rash, performed as well as anything that could be purchased.

Nonetheless, I bought some "thermal plaster" from DealExtreme. It was cheap enough, and works as an adhesive that can be pryed appart if need be. I'll let you know how well it works. But I suspect just using a tiny dab of silicone and pushing the pieces together hard would suffice.

Get an IR thermometer and test it, Hoppy!:smile:


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## Hoppy (Dec 24, 2005)

The last LED light I made I used an adhesive epoxy with lots of ceramic in it, Arctic Alumina, a two part adhesive. It works extremely well, but costs a lot, is a nuisance to mix before using, and Fry's was out of stock on it. I still have some, but it is getting too old to push out of the little syringe type containers. Now I wish I had just used it anyway. However, the stuff I have seems to work ok, and using aquarium cement to glue the lead wires to the heat sink should be adequate to hold the LEDs in place. Once I have it on for awhile I will find out if it works well enough.

I can't afford the IR thermometer!


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## Wasserpest (Jun 12, 2003)

Congrats on 10000 awesome posts. :wink:

If you are looking for cheap IR thermometers, check this. Matter of fact I have a spare, if you want it $12 shipped will work. Doesn't have a laser pointer though, that's why it's fairly cheap.

What I would like to see is a photo of a single T5HO bulb alongside one of the LED channels. Both lit of course, perhaps covered with sheets of paper to diffuse the light. Just to get an overall intensity comparison.


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## IWANNAGOFAST (Jan 14, 2008)

This was a great read Hoppy, I'm thinking of setting this up and for the price you paid, it looks like it'll make more sense to do this rather than replace 3 t5ho bulbs.

Quick question, I'm not so sure on how to read the par readings, but how many of those 3 watt white LEDs would match a 3x39watt t5ho light?


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## Hoppy (Dec 24, 2005)

This shows how I'm using aquarium sealant to attach the lead wires to the heatsink, and those are stiff enough to hold the LEDs in place - the Radio Shack gloop also holds them somewhat, so I think this should work well.


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## Hoppy (Dec 24, 2005)

IWANNAGOFAST said:


> This was a great read Hoppy, I'm thinking of setting this up and for the price you paid, it looks like it'll make more sense to do this rather than replace 3 t5ho bulbs.
> 
> Quick question, I'm not so sure on how to read the par readings, but how many of those 3 watt white LEDs would match a 3x39watt t5ho light?


Two approaches to using LEDs are:
Use enough to simulate a T5HO bulb, putting them close together in rows, like T5HO bulbs.
Or, spread them uniformly over the top of the tank to get very uniform lighting, with no discrete source of the light. This is how I'm doing it, and the way I think will work the best. But, it prevents any side by side comparison to a T5HO bulb.

LEDs vary in how focused the beam of light is. The Cree ones I used before had a narrower beam than these EBay ones have. That means each individual LED provides a dimmer light by itself, but more LEDs contribute to the light at one spot, since their beams are spread out a lot. As a result, for this design, I get significant light from about 28 LEDs at every spot, where with the Cree's I only got that from about 9 LEDs.

These EBay LEDs won't compete with T5HO bulbs. They are very suitable for low light tanks up to about 20 inches max tank height. They would need lenses (optics) attached to each LED in order to narrow the beams a lot, before they could compare to T5HO bulbs. That drives up the cost a lot.


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## Hoppy (Dec 24, 2005)

Wasserpest said:


> Congrats on 10000 awesome posts. :wink:
> 
> If you are looking for cheap IR thermometers, check this. Matter of fact I have a spare, if you want it $12 shipped will work. Doesn't have a laser pointer though, that's why it's fairly cheap.
> 
> What I would like to see is a photo of a single T5HO bulb alongside one of the LED channels. Both lit of course, perhaps covered with sheets of paper to diffuse the light. Just to get an overall intensity comparison.


I don't have a T5 light, so I can't do that, and the comparison wouldn't be fair to the LEDs since they produce a much more diffuse light, the way I'm using them. Perhaps I need to wait and see just how well the completed light does before I brag too much :icon_lol:

I can't see how I would use one of those thermometers, cheap as they are, except for this one project, so I will just continue to use my calibrated finger as a thermometer. Thank you for the offer though.


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## Hoppy (Dec 24, 2005)

*Let there be Light!*










It works! Now, I need to let the aquarium sealant I'm using for wire clamps all dry, and tomorrow I will turn it over, prop it up and measure the PAR it produces. It looks like one of the warm white LEDs is a bit dimmer than the others, but that could be just a quirk of the camera.


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## Jaggedfury (Sep 11, 2010)

That is one bad ass lighting fixture! I've been following this thread and it looks awesome. What's the chance of me seeing this in person.. say the next meeting? I would love a chance to see it in person!


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## VaultBoy (Nov 11, 2010)

Good work Hoppy ive been following youre work with LEDs and I have just recieved most of my parts in the mail and will begin construction soon.

i cant wait to see how this goes on top of a tank


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## Hoppy (Dec 24, 2005)

As usual with my projects, I ran into another snag. Last night I tried to demonstrate this to my wife, plugged it in, and only 4 LED lit up. I unplugged real quickly to avoid burning up those 4. I still had uncured aquarium sealant in numerous spots on the wiring, so I'm hoping the 48 volts I have in the wiring was leaking through conductive sealant to ground. Once I get more awake I will try it again this morning. I did spend some time with an ohmmeter last night, and everything still seems to be right. Oh well, I did get a big thrill when it did work.


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## Hoppy (Dec 24, 2005)

Jaggedfury said:


> That is one bad ass lighting fixture! I've been following this thread and it looks awesome. What's the chance of me seeing this in person.. say the next meeting? I would love a chance to see it in person!


It's 12 days until our next meeting, so I may still not have this installed by then. If so, I will bring it to the meeting and blind all of the pizza customers!


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## Hoppy (Dec 24, 2005)

GOOD NEWS!!

I found one failed LED, and a couple of questionable solder jobs at another LED. I used an ohmmeter to check continuity from the bare wire attached to the LED to the other positive or negative terminal on the LED. That picked up the bad solder jobs. Then, I used a LED tester I made to verify that each LED would light independently, and one wouldn't. Fixing those problems was easy since I have one extra LED. Now it works! I used a few boxes to elevate the fixture off the floor, and some blocks of wood plus another box to get varying distances from the LEDs to the PAR meter sensor, resulting in:










At 18 inches I will have about 45 micromols of PAR, very close to what I designed for. And, the PAR at closer distances (higher up in the tank) is less than it would be with a fluorescent tube light, another design objective. I moved the sensor around to see how uniform the lighting will be, and found that at about 16 inches, the PAR stays +/- 5 over all but the 3 inches or so at front and back of the tank, and out to about 4-5 inches from the ends of the tank. Once I put this over a water filled tank, those drop offs should virtually vanish, due to reflection off the glass and the focusing effect of the water - thus meeting the last objective.

Until I see this on a water filled tank I can't judge the color of the light, but it doesn't seem to be bad.

My wife took a pic of the big test:










Quote: "Why does it have to be so bright?"


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## Hoppy (Dec 24, 2005)

With these LEDs, half pure white and half warm white, spaced 3.25 inches by 3.25 inches this is what you can expect for various LED currents and height above the substrate. I may work up something similar for what happens if you use a different spacing of the LEDs.

You can see that these cheap LEDs can be used very effectively for almost any low light tank. And, don't forget, Tom Barr uses low light exclusively now, and can grow whatever plants he wants, with few if any exceptions.


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## tzen (Dec 31, 2008)

Very nice! Did you wire the entire string in series this time?

I see your beard isn't quite as long as in your avatar image, although you have the same hunched position!


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## Hoppy (Dec 24, 2005)

tzen said:


> Very nice! Did you wire the entire string in series this time?
> 
> I see your beard isn't quite as long as in your avatar image, although you have the same hunched position!


I was older when that avatar image was made :biggrin:

The LEDs are in three series strings of 13 LEDs each, to match the 48 volts put out by the Meanwell driver. The strings are then in parallel, to give each string one third of the 1.3 amps the Meanwell driver puts out.


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## Hoppy (Dec 24, 2005)

Now that I have lots of data with those Ebay 3 watt LEDs I can have fun making graphs to show how they can be used:




















These show what PAR you can get with various LED currents and various LED spacing, at an 18 inch distance from the LEDs to the substrate.


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## BobH (Jan 25, 2009)

Hoppy, thank you for the time you put in bringing your research to light for all of us. I'm going to be building a LED set up in a hood for a 72 bow front in the near future and your work will allow me to do a better job on mine. The LEDs should wind up about 23" above the substrate and it looks like 3" apart at about 350ma should get me around 45 PAR. Did you hold yours back from the edges by the amount of the spacing, 3.25", or something else? Are you happy with the color mix? Bob


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## Hoppy (Dec 24, 2005)

BobH said:


> Hoppy, thank you for the time you put in bringing your research to light for all of us. I'm going to be building a LED set up in a hood for a 72 bow front in the near future and your work will allow me to do a better job on mine. The LEDs should wind up about 23" above the substrate and it looks like 3" apart at about 350ma should get me around 45 PAR. Did you hold yours back from the edges by the amount of the spacing, 3.25", or something else? Are you happy with the color mix? Bob


My LEDs stop about 2 inches from the front and back, and about 3 inches from the ends. Until I can get this on the tank, with water in the tank, I can't tell if the color is what I want or not. It certainly isn't extremely yellow or extremely stark white either, so I suspect it will be somewhat similar to 6700K bulbs. If anything I would use fewer warm white LEDs if I were to do it over. That's largely because I get less PAR from them than from the pure white ones.


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## non_compliance (Dec 1, 2009)

Wow... this thread made my head spin a bit... but very interesting none-the-less. Super cool fixture. THat thing would slap right on my 36" long x 12" wide rimless tank.


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## redfishsc (Aug 29, 2010)

Wonderful thread, Hoppy, I'm disappointed I missed it thus far lol. 

How deep is your 46g?


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## Hoppy (Dec 24, 2005)

redfishsc said:


> Wonderful thread, Hoppy, I'm disappointed I missed it thus far lol.
> 
> How deep is your 46g?


It's about 18 inches high by about 14 inches depth by about 35 inches long. It is a one piece glass front and sides, slightly bowed front rimless tank. It will still be awhile before I have the light on the tank. First I need to re-do the riparium I will keep, putting the best plants I now have in both plus those in my nursery tank all into the remaining riparium. Then I will empty the 45 gallon tank, clean it up, replace the substrate, replumb it a bit, install the light, and finally put water and plants in it. Probably at least 2 more weeks.

Today I discovered that my 39 LEDs are just barely within the voltage the Meanwell driver is now set for. I need to increase the voltage a little so it starts more reliably. When it is cold it doesn't always start now.


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## Cactus Bastard (Jun 5, 2007)

Hoppy said:


> Now I can have fun making graphs


Hoppy, you're awesome :thumbsup:


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## redfishsc (Aug 29, 2010)

Hoppy said:


> It's about 18 inches high by about 14 inches depth by about 35 inches long. It is a one piece glass front and sides, slightly bowed front rimless tank. It will still be awhile before I have the light on the tank. First I need to re-do the riparium I will keep, putting the best plants I now have in both plus those in my nursery tank all into the remaining riparium. Then I will empty the 45 gallon tank, clean it up, replace the substrate, replumb it a bit, install the light, and finally put water and plants in it. Probably at least 2 more weeks.
> 
> Today I discovered that my 39 LEDs are just barely within the voltage the Meanwell driver is now set for. I need to increase the voltage a little so it starts more reliably. When it is cold it doesn't always start now.



You might be able to disconnect all the LEDs and check the voltage under no-load-- should spool up to 48.0 pretty quickly (lol just don't check the current this way under no load lol). I assume you'll turn up the voltage using the SRV1 screw, right? 

Also, you probably already knew this, but you can get considerable current change by fiddling with the SRV2 screw. The two I have here at the house can be dialed down to 400mA and up to more than 1500ma. 


I also found out the other day, helping a friend, that the dimmable versions will work just fine if you only have a 6v reference voltage to give it (ie, nearly any common cell phone charger). We were able to dial the current as high as 1200mA with a 6v dimmer voltage reference by turning up the SRV2 screw. The 10K pot gave us a near 0mA low end and 1200mA top end (Cree XPG). 

I was pleasantly surprised. Everyone has been scrambling to find 9v or 10v regulated adapters, when a normal, common 6v cell phone charger can give you full range.


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## Hoppy (Dec 24, 2005)

redfishsc said:


> You might be able to disconnect all the LEDs and check the voltage under no-load-- should spool up to 48.0 pretty quickly (lol just don't check the current this way under no load lol). I assume you'll turn up the voltage using the SRV1 screw, right?
> 
> Also, you probably already knew this, but you can get considerable current change by fiddling with the SRV2 screw. The two I have here at the house can be dialed down to 400mA and up to more than 1500ma.
> 
> ...


I knew I could increase the voltage quite a bit, but wasn't aware that the current could be adjusted higher instead of just lower. It makes sense that as long as the wattage is less than 48 watts it should be ok to increase either or both. I like the current now, but I will need to up the voltage, probably in a day or so, when I feel like trying it. I'm still quite a few days from having it on the tank. I'm not the type to ever adjust either one once it is set up and adjusted to the PAR I want. I suppose a year or more from now I might want to get back into the CO2 game and want higher light.


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## Hoppy (Dec 24, 2005)

I changed the support for the light to one based on a drawer slide. The other one was annoyingly hard to adjust properly.


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## Hoppy (Dec 24, 2005)

I'm thinking about replacing 3 of the warm white LEDs with red ones, from the same company I got these from, bestshop2008hk. Since these LEDs have such broad beams, the red light would be washed out by all of the surrounding white ones, but it should add more red light available to reflect off red fish and plants. I know one problem with mixing in colors is the colored shadows, but I don't think there will be any shadows anywhere with this configuration. Any opinions, please?


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## IWANNAGOFAST (Jan 14, 2008)

Have you heard of stevesleds.com? The LEDs seem a lot cheaper than else where. 

I'm planning on going down this route, but still unsure of how many LEDs to buy. You're using 40 3 watt LEDs right? And this is for a low light tank?


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## MosMike (Dec 4, 2010)

Hoppy said:


> Since these LEDs have such broad beams, the red light would be washed out by all of the surrounding white ones, but it should add more red light available to reflect off red fish and plants. I know one problem with mixing in colors is the colored shadows, but I don't think there will be any shadows anywhere with this configuration. Any opinions, please?


I had this setup - 11 neutral white and 2 red. Those 2 reds gave red spots on the water surface and red shadows around the aquarium. I removed those reds and everything is fine.


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## Hoppy (Dec 24, 2005)

IWANNAGOFAST said:


> Have you heard of stevesleds.com? The LEDs seem a lot cheaper than else where.
> 
> I'm planning on going down this route, but still unsure of how many LEDs to buy. You're using 40 3 watt LEDs right? And this is for a low light tank?


I checked stevesleds.com - The prices look acceptable, but not cheaper than those from the Ebay company I used.

I have 39 LEDs over a 540 square inch substrate, 18 inches away, powered with 430 mAmps. Using the advertised lumens rating for those LEDs, that gives me about 10 lumens per square inch of substrate at 18 inches, assuming the rated lumens are at 350 mAmps, as they are for Cree XR-E LEDs. And, assuming the graph that Cree supplies for normalized output vs current is typical for LEDs with around 3 watts, I should be getting about 120% of the rated lumens at 430 mAmps. This gives me about 40 micromols of PAR at 18 inches.

A quick and dirty way to pick the number needed for a different tank would be to figure the substrate area, multiply it by 10 for the total lumens needed to get 40 micromols at 18 inches. Then increase it by the square of the ratio of your tank height to 18 inches. That should give you about how many lumenss are needed at 430 mAmps. Divide that by the advertised lumen rating for the LEDs to get the number of LEDs. If you plan to run them at 750 mAmps, divide that number by 1.75. If you plan to run them at 350 mAmps multiply it by 1.2.

To get a different PAR, multiply the number by the PAR you want divided by 40.

Using optics has little effect on this because without optics a lot of LEDs contribute to the PAR at each spot on the substrate, but with optics only a few, as few as one, contribute to the PAR at any spot. So, while the optics cause each LED to give you more PAR, that PAR is concentrated into a smaller diameter circle. I don't think the optics are economically justified.

This crude approximation will not be very accurate, but it should get you into the right ballpark.


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## IWANNAGOFAST (Jan 14, 2008)

whoa you lost me there after find the area of your substrate... the tank is 36x18x18, Looking to get PAR into the 80-100micromol range to match the PAR for 2 to 3 bulbs of t5ho.

648 sq. in of substrate, 24 inches away (tank is 15 inches to the top after substrate, plus light is mounted 9 inches above the tank)


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## Hoppy (Dec 24, 2005)

IWANNAGOFAST said:


> whoa you lost me there after find the area of your substrate... the tank is 36x18x18, Looking to get PAR into the 80-100micromol range to match the PAR for 2 to 3 bulbs of t5ho.
> 
> 648 sq. in of substrate, 24 inches away (tank is 15 inches to the top after substrate, plus light is mounted 9 inches above the tank)


Total lumens you need to get from the LEDs would be 648x10x[24/18]^2 x 100/40=28,800 rated lumens with the LED's driven at 350 mAmps. Divide that by 1.75 if they are driven at 750 mAmps = 16,500 lumens.

If you use the same LEDs I used, an equal mix of Pure white and warm white, they are advertised to give you 130 lumens for the pure white and 110 for the warm white, an average of 120 lumens per LED. 16,500 divided by 120 = 140 LEDs. That doesn't surprise me, because of how much higher your tank is than mine, plus having a bigger surface area. You would have those spaced to 1 every 5.4 square inches, or every 2 3/8 inches both ways.

If you used Cree XP-G LEDs, they have an advertised rating of 130 lumens at 350 mA, about the same as the cheap Ebay ones, but they can be driven safely at 1000 mAmps, to get 2.5 times that much lumens, or 325 lumens per LED. Then you would need about 28800/2.5 = 11,500 rated lumens or 11,500/130=90 (roughly) So, are 90 Cree XP-G LEDs cheaper than 140 of the Ebay 3 watt LEDs? I don't think so, but I'm not sure. The 90 would be spaced 2 3/4 inches apart, roughly. And, you would need a good air cooled heatsink to handle the extra heat they would generate.

Another option is to look up the lumen output of the T5HO bulbs you want to replace, assume that about 3/4 of those lumens can be directed into the tank with the reflectors, and divide that by the 130 x 2.5 = 325 lumens each Cree XP-G will produce, all of which is directed into the tank. Now, if you place those in the number of rows you have of T5 bulbs, you should get about the same PAR.


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## IWANNAGOFAST (Jan 14, 2008)

Wow thanks Hoppy! 

Looks like it's a lot more LEDs than I was thinking of. I was hoping to get away with like, 40-50 LEDs. Perhaps I'll stick with replacing my bulbs for now and just wait for the prices and LED tech to get better


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## Hoppy (Dec 24, 2005)

39 watt T5HO bulbs produce around 3700 lumens. If 75% of that is directed to the tank, that's 2800 lumens per bulb. So, 2 bulbs produce about 5600 lumens, and 3 bulbs about 8400 lumens. Divide those numbers by 325 lumens per Cree XP-G to get 18 and 26 LEDs. That should give you about the same PAR that the T5HO bulbs would give at whatever distance you are interested in. My data suggest that at 24 inches, that would be about 80 and 120 micromols.

The reason this is so much fewer LEDs is that the narrow beams of light from LEDs don't spread out nearly as much as the light from T5HO bulbs. So, you would have bands of light at that intensity under each row of LEDs, but between the bands the PAR would be a lot less. That is different from T5HO lights. If you doubled the number of rows of LEDs to cover those low PAR areas, the number of LEDs about the same as what the other way of guessing gave.


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## IWANNAGOFAST (Jan 14, 2008)

What if I were to use those optics to get a wider spread of light?


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## Hoppy (Dec 24, 2005)

IWANNAGOFAST said:


> What if I were to use those optics to get a wider spread of light?


Almost all optics narrow the beam, not widen it. The beam from the Cree XP-G is about 120 degrees or wider - the optics narrow it to 65 degrees or something like that. I don't use any optics because I want the wide beams to get better uniformity of the light intensity.


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## IWANNAGOFAST (Jan 14, 2008)

ooh ok, I thought it was the other way around. 

We just got a PAR meter over at SFBAAPS, so I'm going to be checking the intensity of my light before I decide how many LEDs to go with. I'm hoping to use the steves led's with 2 rows of light since I'm trying to retrofit it into my existing fixture. Although it may be better to just build my own and sell my current fixture. We'll see. Thanks for the info Hoppy.


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## IWANNAGOFAST (Jan 14, 2008)

Oh boy, running that many LEDs is barely any savings as far as wattage goes. 24x3=72watts, vs 78 for 2x t5ho or 117 for 3x t5ho... plus the fans and what not... I guess the long term savings is in the bulb replacements and not from power usage, unless of course you were replacing halides.


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## Hoppy (Dec 24, 2005)

I think the electricity savings for LEDs are overblown. This new LED light will use about 1.5 watts per LED x 39 = 59 watts, plus a bit more for the inefficiency of the Meanwell driver. It replaces a 55 watt AH Supply light. The big difference will be that I will now have very uniform intensity compared to with the old light, and that is true for most T5 or PC lights. Time will show whether the uniformity is worth the extra watts.

If it proves to be no better than the AH Supply light I will change my LED goals to trying to more closely match T5HO bulbs. Then there will be a savings on electricity.


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## Hoppy (Dec 24, 2005)

It's on the tank now! It works fine, other than that the cantilevering of rhe light causes it to sag a bit at the front when raised. It sags about 1/2 inch. But, I will be using it right on top of the tank as it is now. And, tomorrow I will paint the support column the same color as the wall, so it doesn't stand out as much. The light color looks good, too, a bit warmer than the stark appearance of just pure white.

Once the tank is filled with water the light leakage through the glass on the left will be much reduced, as light will reflect off the glass instead. I don't see any problems with this so far. But, water, substrate, plants, fish, etc. are all to come.


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## [email protected] (Jul 17, 2008)

I like the stand. It's not faputzed at all, but very attractive.


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## Cactus Bastard (Jun 5, 2007)

I agree, the tank itself is very nice too by the way.


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## danakin (Jun 8, 2007)

I come back to TPT to find this. Hoppy, you are a gentleman and a scholar.


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## !shadow! (Jan 25, 2010)

Hoppy said:


> I will change my LED goals to trying to more closely match T5HO bulbs.


l've been experimenting with this for months now. i'll def be keeping tabs on your journal and checking out how or what you do in order to acomplish this.


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## Hoppy (Dec 24, 2005)

!shadow! said:


> l've been experimenting with this for months now. i'll def be keeping tabs on your journal and checking out how or what you do in order to accomplish this.


Until I am convinced that my goal of obtaining the best uniformity of lighting is only a secondary goal, I won't be trying to make a T5HO clone. No question, doing so makes the light cheaper, but it gives less uniform light.


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## redfishsc (Aug 29, 2010)

Looks good! If you decide to chase T5HO efficiency (which you can definitely do and whip), you'll want to pick more efficient LEDs--- the XPG and XML being your best bet. 

You can get the XPG for about $4 at www.ledgroupbuy.com, but you have a wait, just like in any group buy. 

I have a pile of them coming in here soon (hopefully middle of Feb) to send off for spectral analysis. 





Hoppy said:


> If you used Cree XP-G LEDs, they have an advertised rating of 130 lumens at 350 mA, about the same as the cheap Ebay ones, but they can be driven safely at 1000 mAmps, to get 2.5 times that much lumens, or 325 lumens per LED.


If I read you correctly, there are chinese LEDs that are claiming 130 lumens/watt? If so, I would not believe it one bit. There are only a few LEDs that can do this--- Cree XPG, XML, and Luxeon Rebel ES. Other than that, most other LEDs are limited to around 100 lm/w.

Chinese mfr's are notoriously legendary for terrible inflation of their lumen output. I would definitely mistrust any Chinese LED that claims 130 lm/w unless they are using Cree dies (like Edison Opto, and even then I'd be suspicious.)


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## Hoppy (Dec 24, 2005)

redfishsc said:


> If I read you correctly, there are chinese LEDs that are claiming 130 lumens/watt? If so, I would not believe it one bit. There are only a few LEDs that can do this--- Cree XPG, XML, and Luxeon Rebel ES. Other than that, most other LEDs are limited to around 100 lm/w.
> 
> Chinese mfr's are notoriously legendary for terrible inflation of their lumen output. I would definitely mistrust any Chinese LED that claims 130 lm/w unless they are using Cree dies (like Edison Opto, and even then I'd be suspicious.)


Not 130 lumens per watt, just 130 lumens. Divide that by 3 and it is roughly 40 lumens per watt.


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## redfishsc (Aug 29, 2010)

Ah, OK, I got ya. 

The XPG is a real deal 139 lumens/watt at 350mA. I have 12 of them in use right now and LOVE them. They do lose efficiency as you go higher, but man, are they awesome. 


I have a few Cree XML on the way, can't wait to see what kind of retina damage I can do with them.


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## VaultBoy (Nov 11, 2010)

Good work Hoppy... now hurry up and grow something under that light


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## Hoppy (Dec 24, 2005)

This is the high position, the tank maintenance position. It slants back a bit, largely because of the geometry of the drawer slide. I added a couple of "forks", like forklift forks, to help stop the sagging from the weight of the light. That works very well. And, with this slight slant back, it keeps the light out of your eyes as you work in the tank.


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## E.Eliveld (Jun 19, 2010)

*what about heat?*

Hello,

Do you think that the LED setting is generating less heat than the lightning you did use before? (I think one of the reasons for changing to LEDs, beside the light itself, could be the heat that ' traditional' lamps generate.)

Regards,

Erwin


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## Hoppy (Dec 24, 2005)

E.Eliveld said:


> Hello,
> 
> Do you think that the LED setting is generating less heat than the lightning you did use before? (I think one of the reasons for changing to LEDs, beside the light itself, could be the heat that ' traditional' lamps generate.)
> 
> ...


Yes, I know that LEDs generate less heat for the water. Fluorescent lights with polished aluminum reflectors reflect a lot of heat to the water, but LEDs, have no reflectors, so only the light goes to the tank (with some infrared included of course). So far my heatsink has only been barely warm when running, even though the Meanwell driver does get very warm. The driver is still not hot, just considerably warmer than the heatsink. With the driver sitting on top of the light, none of that heat should get into the water.

One think I have now noticed, after running the tank partly filled with water and floating plants for a week, is that I can set the heater to maintain a 75F temperature now. With my PC lights I couldn't do that - the temperature stayed at near 80F whatever the thermostat was set at.


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## E.Eliveld (Jun 19, 2010)

A drop of more than 5F (3C) sounds interesting!


Currently I’m in the process of modifying a second classic Red Sea Max 130 to sweet water (130 liter/34 gallon). Biggest problem with this kind of small type of fish-tank is the heat produced by the lamps. I have 4 thermo controlled fans running and during midst’s of the day I can hear them clearly. The hood on the far-side of the fans is really very warm. I can barely put my hand on it.

Originally the tank has 2x55 Watt T5 power compacts (1 watt-liter/4 watt-gallon) but because I use a dimmer both lamps are only a few hours a day at maximum. Both 10,000K/Actinic lighting tubes I have changed for warm-white.

This time I want to change the lighting to LED’s (and of course the filter) so I’m very interested in you’re experiments and those done by other enthusiasts. Your story confirms what I have red from others, the LED’s itself barely gets warm. 

I’m planning to build a separate power driver and a MosFet as PWM regulator. Initially I will build three regulators but since my dimmer has 4 outputs I have room for one extra if necessary. Anyway, it seems I only need to cool the regulators and they will be on a solid peace of aluminum… With a little luck I will not need fans at all!

Thank you for youre answer,

Erwin


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## Hoppy (Dec 24, 2005)

With the water cleared up, here is the light on the tank. So far, very satisfactory. I still want to get the PAR meter back to make some final measurements, and possibly adjust the LED current. It looks like the water and glass concentrate the light enough to raise the PAR higher than I want, but I have to measure it to be sure. No spotlighting, no color changes across the substrate from the mix of warm and regular white, and very little spillover light. Not much "shimmer" either, but I find too much shimmer is unpleasant to look at.


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## S&KGray (Nov 12, 2008)

Very nice Hoppy, still need to work on my LED fixture. Time is hard to come by hehe.


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## redfishsc (Aug 29, 2010)

That's a beauty, Hoppy. The colors are nice and sunny. 

I suspect you're hitting around 65-75uMols, but that's just a wild guess based on some numbers I've seen on some bare Cree's in similar situations. 


If that's the case, you'll be turning them down some, I suspect. 


The only thing you'll need for more shimmer is just a little surface turbulence--- but since you really don't like it, then it doesn't matter .

I love shimmer, but it looks unusual with a lot of spaced-apart LEDs. Looks scattered and very "disco inferno". 

I think it looks nicer when the LEDs are spaced VERY close together and used as a large, single light source. The ripple "amplitude" is larger and less scattered looking.


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## Hoppy (Dec 24, 2005)

I got the PAR meter today, so I took some measurements in the tank, full of water. I got about 65 mms of PAR at about 16.5 inches, where out in the air I had about 55 mms. So, the water amplifies the light a bit. This is more PAR than I want, so I adjusted the Meanwell driver to drop that to about 50 mms. Near the front glass that dropped to about 40 mms, but best of all, as I got the sensor up higher, the PAR only slightly increased, so at 2 inches below the water surface it was only about 65 in the middle and down to about 40 in various spots between LEDs out to the front of the tank. This is outstanding lighting for my purposes. The PAR doesn't rise rapidly as the sensor gets closer to the top because the closer it is to the LEDs the fewer LEDs contribute light to that spot. That is also why the PAR drops to as low as 40 between LEDs. My goal has always been to get closer to sunlight in uniformity of the light in the tank. I achieved that even better than I expected. Remember: high light is bad, uniform low light across the substrate and vertically too is GOOD!

Now begins the test of the LEDs for durability. They are running 8 hours a day, so after about 20,000 hours divided by 8 hours per day, or 2500 days, or about 7 years I will report back on durability. ( I may have to put this in my will as a task for my grandchildren!)


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## redfishsc (Aug 29, 2010)

Hoppy said:


> I got the PAR meter today, so I took some measurements in the tank, full of water. I got about 65 mms of PAR at about 16.5 inches, where out in the air I had about 55 mms.



d-a-n-g. I guessed it right on the money lol!!! 




> So, the water amplifies the light a bit. This is more PAR than I want, so I adjusted the Meanwell driver to drop that to about 50 mms. Near the front glass that dropped to about 40 mms, but best of all, as I got the sensor up higher, the PAR only slightly increased, so at 2 inches below the water surface it was only about 65 in the middle and down to about 40 in various spots between LEDs out to the front of the tank. This is outstanding lighting for my purposes. The PAR doesn't rise rapidly as the sensor gets closer to the top because the closer it is to the LEDs the fewer LEDs contribute light to that spot. That is also why the PAR drops to as low as 40 between LEDs.


I've noticed the same pattern, regarding PAR and distance, for LEDs. This situation changes though, if you use optics, but it never reaches the crazy changes that some halides have.




> Now begins the test of the LEDs for durability. They are running 8 hours a day, so after about 20,000 hours divided by 8 hours per day, or 2500 days, or about 7 years I will report back on durability. ( I may have to put this in my will as a task for my grandchildren!)


And even after 7 years, as long as you haven't blown an LED, just turn the current up since you have it reduced. 

That is, as long as we can afford electricity in 7 years.....


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## Hoppy (Dec 24, 2005)

redfishsc said:


> d-a-n-g. I guessed it right on the money lol!!!
> 
> 
> 
> ...


In 7 years we will all have a helicopter in our garage? :biggrin:


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## [email protected] (Jul 17, 2008)

Hoppy said:


> In 7 years we will all have a helicopter in our garage? :biggrin:


How do you keep the main blades from springing out of the bungees, when you have it garaged for more than a couple of months? Winter winds make the small one impractical for day to day use.


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## redfishsc (Aug 29, 2010)

Hoppy said:


> In 7 years we will all have a helicopter in our garage? :biggrin:


It would be a sad day for birds if that's the case :icon_neut



What drive current do you have going through the LEDs at this point... or have you been able to check?


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## Hoppy (Dec 24, 2005)

redfishsc said:


> It would be a sad day for birds if that's the case :icon_neut
> 
> 
> 
> What drive current do you have going through the LEDs at this point... or have you been able to check?


Sometime around 1950 or so, "everyone" was sure we would all have a helicopter in our garage in 10 years. I keep repeating the prediction, because some day I may actually be right. Only, I think I will switch to LED aquarium lights for my prediction now.

I don't have an ammeter to measure the current with, nor do I want to break into the circuits to do the measuring, so I don't know what the current is now. My guess, based on how much I turned the pot screw, is about 350 - 375 mAmps. For sure it is now less than 430 mAmps.


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## Arctangent (Feb 22, 2010)

Here is a small scale version of the personal transport vehicle of the future (turn sound up). It's a smart devise that can stabilize, fly, and navigate itself. Another design. Search GRASP quadrotor for more. 

Does anyone have a schematic of the internal workings of a dimmable meanwell? Does it dim using the pot as a current limiting resistor, or as a reference voltage for a PWM modulator?

BTW...Hoppy, how do YOU not have an ammeter? They're like $15 at sears and indespensible.


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## Hoppy (Dec 24, 2005)

Arctangent said:


> Here is a small scale version of the personal transport vehicle of the future (turn sound up). It's a smart devise that can stabilize, fly, and navigate itself. Another design. Search GRASP quadrotor for more.
> 
> Does anyone have a schematic of the internal workings of a dimmable meanwell? Does it dim using the pot as a current limiting resistor, or as a reference voltage for a PWM modulator?
> 
> BTW...Hoppy, how do YOU not have an ammeter? They're like $15 at sears and indespensible.


In 10 years we will all have one of those "personal transport vehicles" in our garage - languishing alongside the old refrigerator that will get fixed some day :biggrin:

I have a multimeter, a cheap one, that has conked out on me just when I need it the most. I have never felt I could afford an ammeter for the rare electronic projects I tackle. The cheap digital ones that were discussed here a few days ago are tempting, though.


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## Arctangent (Feb 22, 2010)

Lol...PTVs

Didn't catch the DMM discussion but you should be able to find one for a reasonable price while still having some assurance of reliability. I'm actually supprised you had one go bad on you (unless it was a $3 Harbor Freight job...had a run-in with these once). I bought a craftsman at a pawn shop years ago, and never had any problems. You don't need a Fluke.

Haven't you posted graphs of par vs. current? Did you have an ammeter then?


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## S&KGray (Nov 12, 2008)

Arctangent said:


> You don't need a Fluke.


True.

I am lucky I can borrow one to use. :icon_mrgr


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## Hoppy (Dec 24, 2005)

Arctangent said:


> Lol...PTVs
> 
> Didn't catch the DMM discussion but you should be able to find one for a reasonable price while still having some assurance of reliability. I'm actually supprised you had one go bad on you (unless it was a $3 Harbor Freight job...had a run-in with these once). I bought a craftsman at a pawn shop years ago, and never had any problems. You don't need a Fluke.
> 
> Haven't you posted graphs of par vs. current? Did you have an ammeter then?


Yes, I have posted graphs of PAR vs current, but most of the data came from Cree, with only single points from my lights, where the constant current supply produced a fixed current. You can accurately calculate the current for many situations with LEDs - at least accurately enough for my needs.


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## Arctangent (Feb 22, 2010)

Just remember that nominal values and ratings are not always precisely true.


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## redfishsc (Aug 29, 2010)

Hoppy said:


> I don't have an ammeter to measure the current with, nor do I want to break into the circuits to do the measuring, so I don't know what the current is now. My guess, based on how much I turned the pot screw, is about 350 - 375 mAmps. For sure it is now less than 430 mAmps.



If you ever want to do this, or potentially separate your array from the driver for whatever reason (I put my driver on top of my canopy, hidden)--- you can use cheap crimp-on male/female disconnects you can get at Lowes. 


If I ever need to check current, I just power off the array, separate one of those quick disconnects, and use alligator clips to connect them to my digital multimeter. Not as nice as the inline, permanent ammeters I am eventually going to buy.. but easy enough if needed.


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## Hoppy (Dec 24, 2005)

redfishsc said:


> If you ever want to do this, or potentially separate your array from the driver for whatever reason (I put my driver on top of my canopy, hidden)--- you can use cheap crimp-on male/female disconnects you can get at Lowes.
> 
> 
> If I ever need to check current, I just power off the array, separate one of those quick disconnects, and use alligator clips to connect them to my digital multimeter. Not as nice as the inline, permanent ammeters I am eventually going to buy.. but easy enough if needed.


I wanted to wire in an ammeter, but persuaded myself that it wasn't cost effective. Accuracy in determining the current has little value, as far as I can see. If you use accuate currents to discuss your results with others, there is no guarantee that they can duplicate your results with a different batch of inexpensive LEDs. And, I knew I would be using a PAR meter to do a final adjustment anyway. I like to eliminate everything that isn't really needed, to keep the cost down, if nothing else. But, that was my method when I worked as an engineer too. Strictly functional, nothing that wasn't essential.


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## Arctangent (Feb 22, 2010)

Sounds good to me, wish I had a PAR meter for when I do my light. What kind of engineer are you? Retired? Future ME here.


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## Hoppy (Dec 24, 2005)

Arctangent said:


> Sounds good to me, wish I had a PAR meter for when I do my light. What kind of engineer are you? Retired? Future ME here.


I'm retired, for 17 years now, after working most of my career for an airline speciallizing in maintenance of hydraulic components, but with the first part of my career spent with NASA, developing hypersonic wind tunnels. It is a great career choice.


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## Arctangent (Feb 22, 2010)

Cool, I'm taking fluid mechanics this semester.


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## malaybiswas (Nov 2, 2008)

How did I miss this thread! You cannot keep your hands off diy led for long, can you . Nice build and very informative thread.


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## Hoppy (Dec 24, 2005)

malaybiswas said:


> How did I miss this thread! You cannot keep your hands off diy led for long, can you . Nice build and very informative thread.


Very true! I wanted to build a LED light again, so I switched a 45 gallon tank from a riparium to a low light tank - and, needed a new light!!

Now, I hope to keep my pants pocket padlocked for a couple of years, but I may run across some interestlngly cheap LEDs before then. If so, I guess I will have to accidentally drop one of my lights.


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## lanea (Jun 28, 2008)

Very informative thread, Hoppy!

I have a question for you as well as other DIY fellows. Can you run multiple Meanwell drivers with just one power cord, that is running them in parallel with one power cord plugging into the outlet? Would this decrease the amperage of the drivers or any other negative effects. My understanding is that this should be fine, correct?

Also, how heavy is your heatsink/hood? You are using 1/16" thick channels so it's about 10 lbs? 1/8" thick channels would make the heatsink/hood somewhere around 20 lbs and that would be difficult to hang or move out of the way. This is another disadvantage I see with LED lighting when using anything heavier than a thin strip of aluminum.

Please let me know your thoughts!


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## Hoppy (Dec 24, 2005)

You can connect as many Meanwell drivers in parallel as you want, as long as the total current isn't more than the house circuit breaker allows, which is probably 15 amps for a wall socket.

My minimal heatsink/housing weighs about a pound or so, certainly less than 5 pounds. As you can see I have it cantilevered out, suspended by one side of the aluminum channel on the back. That is not causing any stress problems. It does sag a bit, because of all of the "stuff" between the wall and the light, but that isn't a problem either. 

The aluminum channel heat sinks do not get hot to the touch, just slightly warm. The hottest part is the Meanwell driver. Incidentally, it is getting more difficult to get some of the Meanwell drivers. Apparently, the vast collection of sizes and features they list for their driver alternatives is mostly just a list, not an actual catalog. But, there are alternative drivers available too.


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## lanea (Jun 28, 2008)

Hoppy said:


> My minimal heatsink/housing weighs about a pound or so, certainly less than 5 pounds. As you can see I have it cantilevered out, suspended by one side of the aluminum channel on the back. That is not causing any stress problems. It does sag a bit, because of all of the "stuff" between the wall and the light, but that isn't a problem either.


That is much lighter than I thought, I was holding 1.25" x 1.25" x 36" with 0.125" thickness and it felt like 2 lbs. That's why I assume four or five of those could easily add up to 10 lbs.

Thanks for confirming the parallel drivers, Hoppy!


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## redfishsc (Aug 29, 2010)

Hoppy, just know about those Meanwells- they can have some enormous inrush currents at start up, presumably because it's charging up the beefy capacitors. It's only momentary but some people on Reef Central have reported issues of using lots of Meanwells on the same breaker circuit, esp. if 3-4 come on at the same time. 

Quoted from Meanwell's page... 
http://www.meanwell.com/faq.html



> At input side, there will be (1/2 ~1 cycle, ex. 1/120 ~ 1/60 seconds for 60 Hz AC source) large pulse current *(20~60A *based on the design of S.P.S.) at the moment of power on and then back to normal rating. This "Inrush Current" will appear every time you turn on the power. Although it will not damage the power supply, we suggest not turning the power supply ON/OFF very quickly within a short time. Besides, if there are several power supplies turning on at the same time, the dispatching system of AC source may shut off and go into protection mode because of the huge inrush current. It is suggested that these power supplies start up one by one or use the remote control function of S.P.S. to turn them on/off.



I have two that come on at the same time, every day, on a 15A breaker and never have had it trip.


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## redfishsc (Aug 29, 2010)

And one very helpful post by Kcress on ReefCentral:

http://www.reefcentral.com/forums/showpost.php?p=17806494&postcount=12


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## Hoppy (Dec 24, 2005)

Unless someone has multiple tanks, each with a Meanwell driver powered LED light, I don't see how this could become a problem. When would you need multiple drivers for a planted tank? But, I appreciate the information - I totally missed that in reading about their drivers. I know that fluorescent lights can cause major problems for electronic light timers, but I had no idea that LED lights were a problem.


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## redfishsc (Aug 29, 2010)

I could see someone with a 6-foot tank running 5 or 6 Meanwells depending on what they were doing. I'm going to be running three of them over a 45g, 23" cube, but running the LEDs at a pretty low current. Just experimenting with piles of colors to see what I can get.

FWIW I do run the Meanwells on a timer-- and never had a single problem, and both of mine kick on at the same time.


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## eklu65 (Mar 3, 2011)

Hey Hoppy, thanks for all the work you've done so far, I can easily say your diy threads are the reason I'm considering the LED route. I just had a few questions:

Based on your graphs on the first page, I'm getting the impression that these LEDs wouldn't be suitable for a 20" high tank, run at your mA. Would that be a fair assessment? Would optics be needed, or would a simple adjustment of the mA be enough? Or would you scrap these and just go for a different set of LEDs altogether?

Also, I had a read through on this thread over at APC http://www.aquaticplantcentral.com/...42-led-experimental-tank-started-later-6.html , and some of those guys were tossing around a 1 LED:24-36^2 inch footprint ratio as a very broad rule of thumb to get a general idea of the number of LEDs needed for your tank. I only had time to read through about half of the thread, so if any other details came to light (...now I'm making bad puns too...) later, I apologize if I may have missed them. What are your thoughts on that after working on your light fixtures?


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## Hoppy (Dec 24, 2005)

eklu65 said:


> Hey Hoppy, thanks for all the work you've done so far, I can easily say your diy threads are the reason I'm considering the LED route. I just had a few questions:
> 
> Based on your graphs on the first page, I'm getting the impression that these LEDs wouldn't be suitable for a 20" high tank, run at your mA. Would that be a fair assessment? Would optics be needed, or would a simple adjustment of the mA be enough? Or would you scrap these and just go for a different set of LEDs altogether?
> 
> Also, I had a read through on this thread over at APC http://www.aquaticplantcentral.com/...42-led-experimental-tank-started-later-6.html , and some of those guys were tossing around a 1 LED:24-36^2 inch footprint ratio as a very broad rule of thumb to get a general idea of the number of LEDs needed for your tank. I only had time to read through about half of the thread, so if any other details came to light (...now I'm making bad puns too...) later, I apologize if I may have missed them. What are your thoughts on that after working on your light fixtures?


The light is now 18 inches from the substrate, and I had to reduce the current a bit to reduce the light to the 40-50 mms of PAR that I wanted. At 20 inches, the intensity would be about 80% of that, still very good. In fact it is still more light than I want - I have to prune rotalas weekly, and some algae keeps trying to establish itself. I now have a digital ammeter ready to install so I can calibrate the PAR vs current, and be able to easily dial in the PAR I want.

This is just one approach to LED lighting - shooting for very uniform lighting over the whole substrate. Possibly a better approach is to use fewer, more powerful LEDs, raised high above the tank. That gives you some nice looking shadows, and shimmer, and reduces the increase in PAR in the upper parts of the tank. If I make another LED light, that is the approach I will use, and then I would use optics on the LEDs.


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## eklu65 (Mar 3, 2011)

> The light is now 18 inches from the substrate, and I had to reduce the current a bit to reduce the light to the 40-50 mms of PAR that I wanted. At 20 inches, the intensity would be about 80% of that, still very good. In fact it is still more light than I want - I have to prune rotalas weekly, and some algae keeps trying to establish itself. I now have a digital ammeter ready to install so I can calibrate the PAR vs current, and be able to easily dial in the PAR I want.
> 
> This is just one approach to LED lighting - shooting for very uniform lighting over the whole substrate. Possibly a better approach is to use fewer, more powerful LEDs, raised high above the tank. That gives you some nice looking shadows, and shimmer, and reduces the increase in PAR in the upper parts of the tank. If I make another LED light, that is the approach I will use, and then I would use optics on the LEDs.


I keep seeing people recommending Cree and Luxeon. Which models in particular would you choose if you were to make another light? I'm pretty interested in that new light idea of yours, considering the shadows and shimmer effect are exactly what I'd like to achieve. I was hoping to hit anywhere between 70-90 mms of PAR, and that target keeps getting lower the more I think about it, especially when considering cost. I guess it would be easier to identify which type of LED to use, then afterward, find out about how many of them I'd need.


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## Hoppy (Dec 24, 2005)

I would use Cree XP-G LEDs, but more LEDs become available all the time, so by the time I would do this there will probably be others that I would prefer.


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## IWANNAGOFAST (Jan 14, 2008)

I'll be building another fixture soon. Just sold off the one I built a few months ago. I will be going w/ 24 xp-g, running at 1050ma shooting for high light this time around, I want some compact growth on some of my stems that I'm not getting now. They're growing, but a little leggy.

I'm going to have them evenly spaced out, and use optics to focus light on the plants that I really want some pop on.

One thing I learned from building the last light, I'm going to be going with some beefier heatsinks so that I don't have to run a fan on the tank.


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## redfishsc (Aug 29, 2010)

eklu65 said:


> I keep seeing people recommending Cree and Luxeon. Which models in particular would you choose if you were to make another light? I'm pretty interested in that new light idea of yours, considering the shadows and shimmer effect are exactly what I'd like to achieve. I was hoping to hit anywhere between 70-90 mms of PAR, and that target keeps getting lower the more I think about it, especially when considering cost. I guess it would be easier to identify which type of LED to use, then afterward, find out about how many of them I'd need.





Hoppy said:


> I would use Cree XP-G LEDs, but more LEDs become available all the time, so by the time I would do this there will probably be others that I would prefer.



Hoppy is right, LED technology does progress, but it's not progressing quite so fast that we can't use the current leaders confidently. 

At the risk of taking over Hoppy's thread as a DIY question/answer, I'd agree with Hoppy that the XP-G is a GREAT option and it's what powers most of what I do. 

That being said, the new XM-L is even more efficient, brighter (at the same drive current) and has a MUCH higher maximum drive current. For a $7 LED that can put out over 900 lumens, that's pretty awesome. 

Most of us would only need a handful of XM-Ls, but if your tank is more than 21" deep, you may need to use the XP-G's in combination with some optic lenses (60 degree). As far as I know, there are no commonly available (ie, affordable) optic lenses for the XM-L. 

You can get them both at ledgroupbuy.com or from Cutter if you need international shipping (outside North America)


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## Hoppy (Dec 24, 2005)

redfishsc said:


> Hoppy is right, LED technology does progress, but it's not progressing quite so fast that we can't use the current leaders confidently.
> 
> At the risk of taking over Hoppy's thread as a DIY question/answer, I'd agree with Hoppy that the XP-G is a GREAT option and it's what powers most of what I do.
> 
> ...


I was hoping you would comment on this. I'm a real noob when it comes to higher powered LEDs, having chosen to work with lower powered ones, in larger numbers. Once I saw that fabulous photo of Jose's tank, http://www.plantedtank.net/forums/lighting/133679-my-diy-cree-led-fixture-w.html#post1352190 using higher power LEDs I have been getting a big itch to try to achieve something like that with a planted tank.


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## hbosman (Oct 5, 2006)

Are the Optic Lenses easily removable? Just wondering if you had specific plant that you wanted to focus on and then moved the plant. Could you move the optic along with the plant? Maybe you wouldn't want to use optics on all of the LEDs so, the color (K rating) of the LEDS would blend better.


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## Hoppy (Dec 24, 2005)

I believe the optics are glued in place, so you could remove them, but not without considerable effort.


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## VadimShevchuk (Sep 19, 2009)

Thank you hoppy for this thread. I must say that i learned a ton from build.


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## eklu65 (Mar 3, 2011)

redfishsc said:


> Hoppy is right, LED technology does progress, but it's not progressing quite so fast that we can't use the current leaders confidently.
> 
> At the risk of taking over Hoppy's thread as a DIY question/answer, I'd agree with Hoppy that the XP-G is a GREAT option and it's what powers most of what I do.
> 
> ...


I'd be designing this light for a 75 gallon, so I'd be right under the 21" mark. I think the XM-L's would be the best option, especially for that price. I believe I'd only need around 18 or so of those LEDs, and I'd definitely have a mix of warms and cools. I'd also prefer to run them toward the upper end of their mA limit as well.



Hoppy said:


> I was hoping you would comment on this. I'm a real noob when it comes to higher powered LEDs, having chosen to work with lower powered ones, in larger numbers. Once I saw that fabulous photo of Jose's tank, http://www.plantedtank.net/forums/lighting/133679-my-diy-cree-led-fixture-w.html#post1352190 using higher power LEDs I have been getting a big itch to try to achieve something like that with a planted tank.


That picture was what finally convinced me to give it a try, haha. It was just too tempting to pass up. Sorry for hijacking your thread, I'm just trying to learn as much as possible at this point. I think I should probably start my own thread for any additional questions. Thanks for your and redfishsc's help, I appreciate it.


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## vee (May 13, 2011)

*Your formula to calculate pars/lumens for tanks*



Hoppy said:


> Total lumens you need to get from the LEDs would be 648x10x[24/18]^2 x 100/40=28,800 rated lumens with the LED's driven at 350 mAmps. Divide that by 1.75 if they are driven at 750 mAmps = 16,500 lumens.
> 
> If you use the same LEDs I used, an equal mix of Pure white and warm white, they are advertised to give you 130 lumens for the pure white and 110 for the warm white, an average of 120 lumens per LED. 16,500 divided by 120 = 140 LEDs. That doesn't surprise me, because of how much higher your tank is than mine, plus having a bigger surface area. You would have those spaced to 1 every 5.4 square inches, or every 2 3/8 inches both ways.
> 
> ...


Could you explain your formula of 
648x10x[24/18]^2 x 100/40=28,800

648= area of substrate
10=?
24= height of light (I'm guessing
18= width of tank?

^2 The entire 648x10x[24/18] to the power of 2??

My tank will be 48"x24"x24"

Thanks!!


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## Hoppy (Dec 24, 2005)

It isn't a formula. I tried to find a crude way to guess how many LEDs producing a known amount of lumens, at 350 mAmps would be needed to produce a specific PAR for a specific tank footprint. At best this would give you a very crude estimate. And, since I did that calculation as I typed, there are very likely some mistakes in it.

Most, if not all Cree LEDs have data available on their PDFs showing the lumens produced at 350 mAmps. Further in the PDF it shows the production of lumens vs current, out to the maximum recommended current for that LED. So, knowing how much PAR someone is getting from X LEDs of type Y, at current Z, over a tank with footprint A, you should be able to do this estimating yourself.


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## vee (May 13, 2011)

I got my hubbie to look at the formula, and he came up with the following and he created an excel spreadsheet. I can now plug in numbers. 

substrate area x 10 x (distance of light to substrate/depth of tank)^2 x desired par/40)

To change to current, multiply the above with (350/desired current)

According to this formula, I will need 31, 360 lumens for a 120 gallon tank (48x24x24). It looks like alot to me, but its something to work with.


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## Hoppy (Dec 24, 2005)

One inaccuracy in that approach is due to using or not using optics on the LEDs. If you don't use optics, and all of the light makes it into the tank, much of that light will be reflected off the glass sides before it reaches the substrate. Each reflection will be as little as half of the incident light, depending on how clean the glass is, and other things. But, if you use optics, possibly all of the light makes it to the substrate unreflected, but with some loss due to the imperfect optics. That is one reason why that approach can only be a crude estimate.

If you design based on that, and design for high light, 100 mms of PAR, for example, then you stand a good chance of having at least low medium light at worst, and with dimmers on the LEDs you can get around it if you get 200 mms of PAR instead. I think that is one of the best reasons for using dimmers, worth the relatively small added cost.

I just used this crude method to estimate what PAR my current LED light will produce, and it says it will be about 80 mms of PAR. In a few days I will be calibrating that light with a PAR meter, so I will find out if the method is at all close - my fingers are crossed.


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## vee (May 13, 2011)

Thanks Hoppy. My hubbie is going to look at some papers that discuss light absorbtion in water in the hopes that we can come up with a more accurate formula (he loves this kind of stuff, being an engineer. I, on the other, am a graphic designer with no skill with numbers).


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## Doc7 (Apr 7, 2011)

Great thread - Makes me wonder if I should stop asking questions to you and others about which brand and configuration of T5HOs to use for a 40 breeder and instead, learn to solder and put one of these together... Then there's no worry about light spread, and with a dimmer, and sized to fit the tank like yours does, dial it in to whatever light intensity I want!

I have a LOT of reading to do...

From the basic calculations you gave, I am thinking that 55 lights arrayed in 5 rows of 11 may be what is suitable for this tank (with 2 inches of space at the front and back of tank from the rim to the center-line of LEDs, this allows for 5 rows @ 3.5 inches on a 40 breeder footprint). How much "dimming" can be done? If the light can essentially be driven at a really low current, it seems to me like, costs notwithstanding, it's not really possible to put _too many_ lights in an evenly spaced array, because they can just be dimmed until the desired PAR value is reached. I need to learn how drivers and dimmers work to truly understand it though. This is all using the 350 mAmps value and the calculations above and I don't even know for sure why or how to arrive at the right combination of current, spacing, and number of lights so read on I shall!


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## Hoppy (Dec 24, 2005)

vee said:


> Thanks Hoppy. My hubbie is going to look at some papers that discuss light absorbtion in water in the hopes that we can come up with a more accurate formula (he loves this kind of stuff, being an engineer. I, on the other, am a graphic designer with no skill with numbers).


Looking at light absorption is the wrong road to follow. The 3 foot maximum tank heights that we see, and even 3 feet is rare, mean there is no significant absorption by the water. The drop in intensity is simply because the cone of light spreads out, "diluting" the light by doing so. The only way to stop that "dilution" is by using lasers to light the tank - a beam that doesn't get bigger with distance. (Or by hanging the light 100 feet above the tank!)


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## redfishsc (Aug 29, 2010)

Oh you can get 2 degree optics for LEDs, I saw some for XML's the other day--- don't think I wasn't tempted to buy 6 of them since I have 6 spare XML's right now.... if only I can find a 3-amp driver that will run 6 XML's.


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## Doc7 (Apr 7, 2011)

Does one need a multimeter to appropriately set this up? they're available to me so I can use one, but just wondering if the Meanwell voltage and amperage pots have indications on them or it is a matter of testing to get the desired values. I tried to google image for the adjustment screws but didn't find what I was looking for.


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## Hoppy (Dec 24, 2005)

The adjustment screws are not really visible as you turn them, and there are no markings to go by anyway. I raised the output voltage of my driver, because I found that cold LEDs wouldn't reliably start without me doing that. I just turned it slightly, and tested it for starting. I adjusted the current a bit by using a PAR meter so I could get the PAR I wanted. When I get around to it I plan to install a digital ammeter in the LED circuit so I can calibrate the light, with a PAR meter. Those digital ammeters sold on Ebay are very cheap and effective for this.


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## andyl9063 (Oct 22, 2010)

hey hoppy,

for someone looking to spend a lot of money on this, how reliable are those led lights?
Do we have any testing that tells how long they last?


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## cggorman (May 9, 2009)

Life varies greatly depending on the temperature and current. Life projections are generally measured in hours to 70% output; when the diode can only emit 70% of its original light output. This can range anywhere from 10,000 hours to 100,000 hours. Most Cree diodes are rated around 35,000 hours (driven to max current/temp) , I think.

Failure is generally seen as a dimming over time rather than a catastrophic failure like a traditional bulb.


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## Hoppy (Dec 24, 2005)

LEDs are somewhat like computers - they become obsolete in 2 years, replaced by much better ones. So, I doubt if anyone has operated an LED aquarium light long enough to verify that they will last 50,000 hours (at 8 hours a day, that's 6250 days, or 17 years) and even if they have, it would be with 5 mm LEDs, which are so obsolete they are now fossilized.


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## Robbie1990 (Jun 16, 2011)

i have always wondered about the solder joints and bare leds above a tank, what if they get a bit of moisture off the tank? do they not need sealed up some how?


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## Hoppy (Dec 24, 2005)

I have never seen any moisture collecting on my LED lights. They do get warm, so when they are off any moisture just evaporates. And, this particular light normally sits right on top of the tank, where the exposure to moist air is the highest.


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