# LED Heatsink thread: Where to find them, what to look for....save cash!



## redfishsc (Aug 29, 2010)

I'm starting this thread so that we can put together a group effort on making this sometimes frustrating part of DIY LED work much easier. 

*Please share your experiences/sources/DIY methods for affordable heatsinking.* *Feel free to ask any question about selecting a heatsink.*

I'll admit I'm a firm believer in overkill with heatsinks-- it's good insurance in case I ever decide to crank up the current, but it's not always affordable. Lots of people use aluminum C-channel and similar flat stock, I personally advise you to use stuff that's a minimum of 1/4" thick and 1.5" wide, but if you run the LEDs at low currents, then you can possibly get away with thinner.

For info on thermal adhesives and epoxies, etc.... look at post #3.

So here are a couple resources for _*legitimate*_ manufactured heatsinks that do a very good job. 
*For LARGE, individual LEDs (10 watts and higher) *

It's hard to beat star-shaped heatsinks like these, made by Wakefield, at a very reasonable price:

http://www.newark.com/jsp/search/br...=200539+104931&displaytext=&_requestid=503476

(Newark also sells the wonderful HUGE and powerful Bridgelux LEDs so you can order both from the same place). 


There are also some nice heatsinks and lower-cost "import/generic" type LEDs available at Satistronics.com

http://www.satistronics.com/Wholesale-led-lamp-lightings-heatsinks-for-led_c1027

I'm partial to this one, it comes drilled, tapped, with screws included that fit their larger LEDs.
http://www.satistronics.com/high-po...r-10w20w-and-30w-power-led-90mm30m_p2162.html



*For larger arrays using many LEDs*, the beefiest and most affordable heatsinks I'm aware of-- and the ones I use on most of my stuff--- is the custom-cut offerings from:

www.heatsinkusa.com (see posts BELOW on selecting a heatsink size for your tank, don't spend too much for an oversized heatsink)


*Finally, if you are lighting a small tank*(5.5g or smaller, or something that's under 15" long) you can also just use leftover computer CPU heatsinks, and possibly even the fans if you need it. 

There is no real reason you couldn't use multiple CPU heatsinks over a large tank as long as you don't overwork them by using too many LEDs and high drive currents.


Now please, everyone share your sources, or your DIY work.roud:


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## redfishsc (Aug 29, 2010)

On selecting the size of the heatsink if you are going with a custom cut size from a site like HeatsinkUSA....or if you are replicating this by using aluminum C channel. 

There is no magic formula, and there are several factors that interfere with making a cookie-cutter formula. The angle (or absence) of optic reflectors, the height you hang the array at, the number of LEDs, and the intended drive current all effect the size of the heatsink you'll likely need. 

BUT!

I think the following criteria is helpful. If you are building a typical LED array, that uses 60 degree (or bigger) optics, and are using a larger number of 3-5w LEDs (like Cree XRE/XPG/XML types), you'll basically want two rows of LEDs, 3" apart, for most tanks that are 10-15" wide. So two rows, centered, with 3-4" in between them.


It needs to be about 1/3 the width (not length!) of your tank. In other words, for a 55g (13" wide), you would want a heatsink that's about 4" wide. 



For length, this is much easier. Just knock a few inches off of the length of your tank. So a 48" long tank would need a heatsink that's 42-47" long.


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## redfishsc (Aug 29, 2010)

Regarding thermal adhesives. You have a few good options. 

Most of us, who don't work the death out of LEDs can just use whatever cheap thermal adhesive you can get at any computer place. Make sure it's a grease that never evaporates.


*Option #1, the best option:
*Arctic Silver Thermal _Compound_ and similar products. This IS NOT A GLUE and won't hold the LED in place for long. You MUST drill/tap your heatsink and screw the LEDs down... or some other way of attaching the LED. The screw and thermal grease method is probably the most effective, but most SWEATY and labor-intensive method. Fortunately some places like RapidLED.com sell pre-drilled heatsinks. Well worth it. 

http://www.arcticsilver.com/as5.htm


*Option #2 (not best, but very good): *Thermal Epoxy/Adhesive. 

Arctic Alumina Thermal _Adhesive_ (and the similar Arctic Silver Thermal Adhesive) is a VERY STRONG two-part, mix-yourself epoxy. A very little goes a very long way. This is a permanent glue joint that you may never be able to undo once you glue it, so make sure you have that LED where you want it! This is mildly less effective than the thermal grease above, but quite effective anyway. Benefit--- you only need to secure the LEDs while it's curing, which is only a few minutes. 

http://www.arcticsilver.com/arctic_alumina_thermal_adhesive.htm


*Option #3 *(quick, easy, and effective, but #3 in terms of efficiency):

Thermal Tape/pads.

Bergquist Bond-Ply is a very good product, and for our purposes, is VERY effective and by far the quickest, cleanest way to do this. This is mainly what I use. 

Here is a 6" square sheet for $22, but keep in mind that this is enough to do at least 40 LEDs (3/4" squares). If you are good with the razor knife, or use a paper-slicer, you can actually get 48 out of it. Newark also sells nice Wakefield heatsinks for individual, LARGE LEDs and also the lovely Bridgelux higher-power LEDs, all at very good prices.

http://www.newark.com/bergquist/bp100-0-008-00-1212/bond-ply-100-008-6-x-6-sheet/dp/47T1948


Here are the pre-cut ones you can get from aquarium-spec shops.
http://www.nanotuners.com/product_info.php?cPath=74&products_id=627
http://www.rapidled.com/servlet/the-169/Berquist-Thermal-Pad-(individual)/Detail


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## jcgd (Feb 18, 2004)

I noticed a lot of people get their c-channel from Home Depot. IME Home Depot isn't the cheapest source for this kind of material. I called around and found a metal wholesaler and got exactly what I want, cut custom. They also have scrap bins you can pull from. It's easy to cut a deal with that stuff because they consider it waste.

Another thing I noticed is that most people are still putting their fixtures right above the tank. LEDs are nice and powerful so if you have a rimless or open top tank, why not hang that light up nice and high? Optics are cheap cheap and if you slap 40 degree optics, you can raise your fixture up a couple feet and their are lots of advantages. The spread can be the same, or adjusted for less spill, more power from your LEDs, easy access to the tank and best of all, more consistent par levels throughout the tank. As you get further from a light source the difference in par becomes less. Close to the light is drops off very quickly, but get the fixture up there a bit and the par levels at the surface and substrate will be much closer together than if the fixture is on the rim. 

Also, almost everyone goes waaaaay overkill on their number of LEDs. Take a look at all the other builds and notice how everyone ends up dimming their fixtures down. Also consider that in 5 years, XPG will be history. So don't be afraid to run a decent current through them. They are good for 1500mA, so you don't need to limit your current to 700mA for fear of burning them out early. You probably wont be using the same LEDs in 15 years. Think about utilizing the power they have.

Just some food for thought.


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## cggorman (May 9, 2009)

My testing has shown that it takes approx. 40 square inches of surface area to maintain touch-safe temps for a 5 watt led driven to it's limits.

This requirement falls off FAST as the drive current is reduced. The above test was pushing the diode at 1.5 amp and resulted in heatsink temps of approx. 130°F. Dropping the drive current to 1.2 brings the heatsink down to about 100°F. (room temp was 72°F)

This is passive cooling and a finned aluminum heatsink. Adding a small fan drops the temp down to near ambient.


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## h2oaggie (Feb 28, 2011)

Very good thread. I think the more information we can collect in one place the easier DIY LED builds will be for others in the future. 

For my own build, I used 12 XP-G's, separated into two rows of 6. Each row was placed in 2"Wx1H" 1/8" thick aluminum channel, 28" long. Running at 1 A, I have no heat whatsoever, the channel is maybe 5-10 degrees above ambient (78). This was using Arctic Alumina thermal adhesive.


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## cggorman (May 9, 2009)

h2oaggie said:


> Each row [of 6 XP-Gs] was placed in 2"Wx1H" 1/8" thick aluminum channel, 28" long. Running at 1 A, I have no heat whatsoever, the channel is maybe 5-10 degrees above ambient (78). This was using Arctic Alumina thermal adhesive.


I show that channel as having approx. 218 square inches of surface area, or a bit over 36in^2 per LED. That jives with what I got. roud:


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## O2surplus (Jan 31, 2010)

Here's an other overlooked source for heat sinks- *Car Audio shops* Broken car amplifiers can be used for their heat sink and often times purchased very cheaply or had for *free.*I used 3 of them in my very first build. 30 Cree XR-Es consuming 5 amps total, and barely warm to the touch. Here's a photo of one-


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## redfishsc (Aug 29, 2010)

cggorman said:


> My testing has shown that it takes approx. 40 square inches of surface area to maintain touch-safe temps for a 5 watt led driven to it's limits.


Using what thickness heatsink, with what fin type/size/number?

The heatsinks from Heatsinkusa, and those big star heatsinks from Satistronics can handle quite a bit more wattage than 5w at 40 sq inches. 

The star heatsink I used on a 10 watt emitter (at 1000mA) was about 4" diameter, with a center solid aluminum cylinder about 1"X1", the rest was fins.


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## redfishsc (Aug 29, 2010)

O2surplus said:


> Here's an other overlooked source for heat sinks- *Car Audio shops* Broken car amplifiers can be used for their heat sink and often times purchased very cheaply or had for *free.*


And AWESOME point. Thanks!


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## cggorman (May 9, 2009)

redfishsc said:


> Using what thickness heatsink, with what fin type/size/number?
> 
> The heatsinks from Heatsinkusa, and those big star heatsinks from Satistronics can handle quite a bit more wattage than 5w at 40 sq inches.
> 
> The star heatsink I used on a 10 watt emitter (at 1000mA) was about 4" diameter, with a center solid aluminum cylinder about 1"X1", the rest was fins.


 
Right. More fins in a given volume means more surface area.

The sinks I was testing were cannibalized computers heatsinks. One was a large northbrige heatsink around 20 in^2 with pins (not fins) and the other was a CPU heatsink that I cut into 4 equal pieces about 1.5x1.5 I also did another CPU sink with 4 diodes mounted to it. 

Of course, there is also the large tubular air manifold I built for my corner tank setup. It is approx. 925 square inches of surface and holds thirty 5 watt diodes. That's about 30 square inches each and it gets quite warm when all the diodes are driven to 1.5 amp. I didn't put a probe on it, but I would guess 130°F. I measured it last night and got 104°F with the diodes running at 1.2 amp. (room temp was 77°F). This is an ACTIVE cooling setup. Fans push air thru the inside of the tube at a theoretical speed of about 750 linear feet per minute. (I don't know what kind of loss I'm seeing from friction in the tube. I could borrow an anemometer from work to measure it, but don't care that much  )


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## Hoppy (Dec 24, 2005)

O2surplus said:


> Here's an other overlooked source for heat sinks- *Car Audio shops* Broken car amplifiers can be used for their heat sink and often times purchased very cheaply or had for *free.*I used 3 of them in my very first build. 30 Cree XR-Es consuming 5 amps total, and barely warm to the touch. Here's a photo of one-


What are the dimensions of these? If I ever make another LED light this would be something I will consider.


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## redfishsc (Aug 29, 2010)

Hoppy, they all vary in size but I think common sizes (depending on what you ripped them from ) will be 4X8, 8X10, etc..

You can get them off of used audio amps and also off of used AC/DC automotive converters.


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## pucksr (Jan 27, 2011)

*Why is thickness even in the equation?*

I keep hearing "thickness" thrown around...but I have no idea why...

I suppose thickness would be important if you were trying to optimize thermal conductivity between source and a large surface area...but not that big of a deal considering the junction between the diode and the heatsink will be your largest bottleneck. The main concern should be the surface area of the heatsink(to a point).

Here is my point. Would it be better to buy 1" L stock(1" x 1") at 1/8" or 1" flat at 1/4"? I would double my surface area with the L and use the same amount of material(roughly the same cost).

Finally, unless you have some reason for "super-cooling" your LED rig I dont know why people get so worried about getting it "cool to the touch". These LEDs will run easily up to 90 degrees C.(you could estimate a thermal drop of about 30 degrees between LED and sink). All 90 degree C does to life is cut it by about 50%. That means that with a worst case temp drop from junction to heatsink of 30C(which is pretty lousy) and getting your heatsink up to 140F...you would have to change your lights out in 6 years when the cost of the original LEDs will probably be close to $1 a piece. So...if you have 24 XP-Gs and you buy a $60 heatsink instead of 2x$5 pieces of stock aluminum all you are doing is spending more money and losing out on the possibility of upgrading in 6 years.


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## redfishsc (Aug 29, 2010)

pucksr said:


> I keep hearing "thickness" thrown around...but I have no idea why...


I assume you are referring to as "throwing around" thickness. The reason I suggest thicker heatsinks is because I see so many people wanting to use cheap/easy to find 1/16th thick aluminum, which is (IMO) quite inadequate. They might get away using 1/16th stuff if they only run the LEDs at 350mA or less, but not all of us do that. 


Safer is better than sorry. 



Two materials of the same square footage, but of different thicknesses, will have different abilities of heat sinking. But you know that already. LED's will create a hot spot directly behind the star, in the spot you mentioned which is the real weak link (the spot between the LED star and the heatsink). That hot spot is greatly cooled by more mass in the immediate area of the LED. Thickness is a very effective, simple way to do this.





> The main concern should be the surface area of the heatsink(to a point).


It is, and nobody is arguing against that, but the use of even thermal two-sided tape seems to be perfectly sufficient. This might be the most important part, but it's actually one of the easiest to accomplish to a sufficient degree.



> Here is my point. Would it be better to buy 1" L stock(1" x 1") at 1/8" or 1" flat at 1/4"? I would double my surface area with the L and use the same amount of material(roughly the same cost).


The extra surface area would definitely give you more passive cooling, but is there enough mass right near the LED to wick away the heat? At 1/8" thick, maybe up to around 500mA, I don't know for sure. 

I'll test it soon, I have some 1/8" thick flat stock I'll use over a shrimp tank, as soon as my drivers make the ever-so-slow transit in from DX.



> Finally, unless you have some reason for "super-cooling" your LED rig I dont know why people get so worried about getting it "cool to the touch". These LEDs will run easily up to 90 degrees C.(you could estimate a thermal drop of about 30 degrees between LED and sink). All 90 degree C does to life is cut it by about 50%. That means that with a worst case temp drop from junction to heatsink of 30C(which is pretty lousy) and getting your heatsink up to 140F...you would have to change your lights out in 6 years when the cost of the original LEDs will probably be close to $1 a piece. So...if you have 24 XP-Gs and you buy a $60 heatsink instead of 2x$5 pieces of stock aluminum all you are doing is spending more money and losing out on the possibility of upgrading in 6 years.



Reasonably good point, especially if using import low-cost LEDs. But buying more expensive heatsinks isn't costing you the opportunity to upgrade in 6 years by using a larger heatsink. You're actually postponing the need to upgrade in 6 years. You may get 10-15 years. 

Using a smaller, less effective heatsink is potentially forcing you to upgrade quicker, or forcing you to swap out a blown LED when one fails, which can happen.

We don't know just how much the LED scene will improve over the next few years. It may be leaps and bounds, maybe not. I think spending the extra cash on a larger heatsink is well worth it, but then again, that's the whole point of this thread---- how to save money and still have "definitely sufficient" heatsink. Not "somewhat sufficient".


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## Hoppy (Dec 24, 2005)

pucksr said:


> I keep hearing "thickness" thrown around...but I have no idea why...
> 
> I suppose thickness would be important if you were trying to optimize thermal conductivity between source and a large surface area...but not that big of a deal considering the junction between the diode and the heatsink will be your largest bottleneck. The main concern should be the surface area of the heatsink(to a point).
> 
> ...


You raise some good points. From everything I read the safe temperature for LED junctions is high enough to burn you if you touch it. Keeping it "cool" isn't necessary, just keeping it within the safe temperature range. I like to use 1/8" inch thick or thicker aluminum mostly because intuitively I think that will work best. It will get the heat away from the junction area faster. 

There have been several threads here where people used strips of aluminum bar stock as heatsinks, apparently successfully, but no one can know if those will still be working in 5 years. On the other hand, as you pointed out so well, in 5 years the LEDs they used will be considered throwaways, they will be so cheap.

My experience makes me think that if I can get 3 years out of a LED light I will probably be longing to make a better one long before then anyway.


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## jasonpatterson (Apr 15, 2011)

For my nano I made a light with a 3 LED star and because of the setup, a cookie jar with a glass lid that pretty much had to be in place, I had some unusual restrictions for the heat sink. 

For the heat sink I wound up using a small piece of 1.25" aluminum round. I drilled out the center of it to a depth of approximately 1.5" then cut flutes into the edges and spread it out like a flower. (Went slow with a drill press, a spade bit, and a vise. It worked beautifully.) The LED rests against approximately 1" of 1.25" diameter aluminum and has 10 1" long petals that disperse the heat to the air. The original configuration, which involved almost no airflow around the base of the heat sink, didn't work particularly well and was prone to overheating. A slightly modified version that exposes the entire thing to airflow works amazingly well.

I got the aluminum round from www.onlinemetals.com. If I were going to do this again, I would start with a 1.5" round instead of 1.25" and make the petals of the flower longer. I might even drill into the rod from both ends and have a double set of petals.


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## redfishsc (Aug 29, 2010)

I'd love to see a pic of this Jason. My eyes will tell me more than my mind can picture .


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## tzen (Dec 31, 2008)

For my heat sink I used aluminum bar I got from EBay. 1.5"x0.5". It was pretty cheap, and had copious thermal mass. Downside from using bar instead of c-channel was that the LEDs would be sticking out. I used a router to make insets for the LEDs, but alternatively, you could build your fixture so the bars and LEDs were set back from the bottom.


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## redfishsc (Aug 29, 2010)

You could also put downward "fins" on the thick bar using some thin lumber (w/stain and varnish for a nice look), or use slits of nice looking laminate glued on with 3M adhesive spray, or any other number of things, to reduce glare.


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## jasonpatterson (Apr 15, 2011)

Here's a picture of the heatsink. It rests inside the lid of the cookie jar. It originally was seated inside the handle portion of the lid (bottom in the picture) but there wasn't enough airflow. I attached a small chunk of a standard finned heatsink (perhaps 1.5" square) as a spacer between this and the glass. The entire assembly and LEDs are cool to the touch while operating. I've had it running as high as 700mA/6W without any heating issues, but I usually keep it at 350mA/3W to suit the tank that it's lighting. 

Cutting the heatsink so that there were more petals and spreading them out helped with heat issues substantially (not terribly surprising...) 

It also needs a bath.


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## reybie (Jun 7, 2007)

Will 14 CREE XPGs be enough to cover the footprint of a 90P (36x18x18)?

Edit: I forgot to add that each one has 65 degree optics.

Edit2: I came across this calculator from a link on reefcentral... looks like a good rough estimate of coverage.
http://www.trashboard.de/wp-content/uploads/illumination.swf


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## redfishsc (Aug 29, 2010)

reybie said:


> Will 14 CREE XPGs be enough to cover the footprint of a 90P (36x18x18)?
> 
> Edit: I forgot to add that each one has 65 degree optics.
> 
> ...




I am using 14 XPG's over EXACTLY half that footprint. 

I have a 36X9X9 11g tank. 

Now, I'm only running my LEDs at 400-500mA.

If you run yours at 1,000 to 1,500mA, it may be enough but it depends on several things, mainly what light level you want. 


Honestly I'd go with Cree XML's instead if you haven't bought the LEDs yet. They are a little bit brighter and more efficient, but not by a huge amount. But you can run them up to 3,000mA which is nuts.

I think you'll be fine but definitely get a dimmable driver that can run the LEDs at 1300-1500mA if you go with XPG. 


No optics, by the way, unless you plan on raising the light a good 20-25" off the surface of the water.


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## reybie (Jun 7, 2007)

It's actually assembled already and it comes with a mean well driver. I will check out the model number - it is dimmable, one of our local members built it and I was thinking of reusing it inside my tek shell 

I'm going for med-high lighting, I've got an iwagumi scape thing going (trying anyway), but it could change to stems again in the future.

I'm not sure if he used adhesive to mount it to the heatsink, hmmm.


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## Dragonfish (Apr 28, 2011)

I think I may have the cheapest heatsink here! I used a 1/8" thick piece of aluminum I cut out of a server motherboard tray that was going to the recycler. Then I attached a video card heatsink to it with thermal paste. I used the stock fan that it came with and was extremely quiet. The farthest point from the heatsink was about 6" and it got hot, but I could touch it without being burned. Since I had it all lying around it was free but you can get super cheap video card heatsinks on [Ebay Link Removed]


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## jcgd (Feb 18, 2004)

reybie said:


> Will 14 CREE XPGs be enough to cover the footprint of a 90P (36x18x18)?
> 
> Edit: I forgot to add that each one has 65 degree optics.
> 
> ...


I'm starting to think that everyone is using up to twice the number of LEDs required. Most people drive the LEDs really low, because they have too much light. Many also don't use optics. If you raise the fixture, use optics and drive the LEDs at 1000mA instead of half, you get more even par throughout the tank and you could end up with the same amount of light with 1/3 less or 1/2 as many LEDs because of the optics.

I need to get a par meter, but I want to lay down some hard evidence to prove my point. Right now it's a educated guess but I think I am right.

Everyone on the reef forums gasps at the ridiculousness of using half the number of XLMs than XPG. The two reasons I get the most are spotlighting, and the problem of dissipating the heat from the XMLs at 2100mA or so. So raise the darn fixture. The tighter the optics, the more light you get (and spotlighting) but the light level will be too high, so you raise the fixture to reduce spotlighting, and this also creates more even par levels through the tank, top to bottom.

If you are using a decent heat sink, at 1000mA your sink doesn't really get warm. My T5HO fixture is hot hot. Not my LED sink. [STRIKE]I strongly doubt the XMLs are going to make the fixture too hot. If you can leave your finger on the heat sink, even if it hurts, the fixture is cool enough. Obvously if your finger is getting burnt it's too hot, but slightly painful isn't too hot. The max temperature of the junctions of these LEDs is 150C. That will burn you instantly. Anything under 60C will be fine. [/STRIKE]

*Redfish made some good points in a post below, and because I can't be 100% sure of my comments, I take them back. I believe the logic is sound, but can't stand by it completely.*

So, I'm assuming those LEDs on the fixture you are looking at aren't in a single row. If they are you have problems, but two rows will work pretty well. The think is, you will have to drive them at a higher current, and you will need the fixture up pretty high to get a good spread. Most of the light is in the middle half of the cone angle, so 33 Degrees. To get a good spread front to back with two rows you will need that fixture up pretty high. IMO I say try it and if it isn't enough light, add more LEDs.


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## redfishsc (Aug 29, 2010)

justincgdick said:


> If you are using a decent heat sink, at 1000mA your sink doesn't really get warm. My T5HO fixture is hot hot. Not my LED sink. I strongly doubt the XMLs are going to make the fixture too hot. If you can leave your finger on the heat sink, even if it hurts, the fixture is cool enough. Obvously if your finger is getting burnt it's too hot, but slightly painful isn't too hot. The max temperature of the junctions of these LEDs is 150C. That will burn you instantly. Anything under 60C will be fine.



Please be careful with this advice. You say that 150C will burn you instantly (agreed). 

The problem with this is that the junction temp, where the LED meets the star, will likely be much, much hotter than the actual temp of any other point on the heatsink. (which you probably already know)


In other words, if your heatsink fins are HOT, then the junction temp is EXTREMELY hot.


I'm not saying this necessarily to "correct" you, since I don't have any hard data to prove anything, but my suspicion is that if the heatsink is causing you any pain whatsoever (even tolerable discomfort) then you are wearing your LEDs out more than necessary via insufficient heatsinking.


My advice is this--- until we have a way to reliably predict or measure the junction temperature----- we should overkill our heatsinks and shoot for "hot but not uncomfortable" to the touch as our maximum "temp". 

That's not scientific, it's not all that accurate, it's not all that objective. But. It is a sure bet that things are within tolerance. 

On a small tank, no big deal. A few blown LEDs is cheaper than a big beefy heatsink. But on a bigger tank with a couple dozen LEDs, a good heatsink is a very very good idea.


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## DarkCobra (Jun 22, 2004)

You might build a fixture from a "cold sink" instead. :hihi:










Once available on TV for $19.95, plus shipping and handling.

Now available at garage sales and thrift stores for pocket change. As well as other repurposable goodies. Switching power supplies have become so common I don't think I'll ever have to purchase another one new.


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## bustah8 (Dec 23, 2010)

Can anyone tell me if there are any noticeable differences in efficiency between cast aluminum vs. extruded aluminum?


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## jcgd (Feb 18, 2004)

redfishsc said:


> Please be careful with this advice. You say that 150C will burn you instantly (agreed).
> 
> The problem with this is that the junction temp, where the LED meets the star, will likely be much, much hotter than the actual temp of any other point on the heatsink. (which you probably already know)
> 
> ...


This is a very good point. Without numbers (that I don't know how to get) it is really hard to say what is okay and what isn't. I completely agree with you. I don't think anyone should avoid a heatsink. If you are running XRE or XPG at less than half the rated current I believe c-channel will suffice. But I don't recommend skimping on a good heatsink if you are running some serious current/ lots of LEDs, etc. I'm only saying that if you can touch the heatsink, your are probably safe.

I just ran my fixture for about 10 minutes at 2A and it got hot. Not painful, but it was very warm.

I agree that I overstepped myself in saying that if it's too hot to touch, you could be okay. Without hard data, I take that back. However, if you can touch it without pain, I think it should be fine.


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## redfishsc (Aug 29, 2010)

bustah8 said:


> Can anyone tell me if there are any noticeable differences in efficiency between cast aluminum vs. extruded aluminum?


Unless you are planning on using super-thin pieces where a slight difference in thermal conductivity would be a HUGE deal breaker, don't fret it. 

Either one will work. The big deal is making sure you have a good thermal joint between the LED star and aluminum heatsink, and that's quite easy to do for our purposes.


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## Dragonfish (Apr 28, 2011)

I didn't see this option mentioned. Here's a 48" long extruded aluminum T-slot with a 2" flat side dirt cheap. It would even look cool just bare without a fixture.

http://www.amazon.com/80-25-5013-T-SLOTTED-EXTRUSION-1220mm/dp/B001F0LV9I


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## Hoppy (Dec 24, 2005)

Dragonfish said:


> I didn't see this option mentioned. Here's a 48" long extruded aluminum T-slot with a 2" flat side dirt cheap. It would even look cool just bare without a fixture.
> 
> http://www.amazon.com/80-25-5013-T-SLOTTED-EXTRUSION-1220mm/dp/B001F0LV9I


That is a great find! Ideal for a row of LEDs, and even has channels for wiring.


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## speedie408 (Jan 15, 2009)

Subscribed for future LED endeavors. VERY informative and exactly what I was looking for. 

Can someone explain about "drivers" and what types are available along with the type of LEDs available and where to buy them? I keep hearing "dimmable" but how does one install such a device?

*edit* sorry for the HIJACK... maybe someone can just link me to another thread that's relevant to my questions?


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## reybie (Jun 7, 2007)

This one is a good primer.


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## redfishsc (Aug 29, 2010)

Dragonfish said:


> I didn't see this option mentioned. Here's a 48" long extruded aluminum T-slot with a 2" flat side dirt cheap. It would even look cool just bare without a fixture.
> 
> http://www.amazon.com/80-25-5013-T-SLOTTED-EXTRUSION-1220mm/dp/B001F0LV9I


Yeah Hoppy is right, that is a good idea. You could easily make an entire light for a 75g tank using only two of these, totaling around $30-45 depending on shipping costs. 

The only modification I would make would be to use a table saw to score a groove down the middle of the heatsink on the topside, to open up that triangle in the middle, so that the sides of the triangle act as heat fins and hot air can rise up.

I'd only bother with that if running the LEDs more than 600mA though.


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## speedie408 (Jan 15, 2009)

Dragonfish said:


> I didn't see this option mentioned. Here's a 48" long extruded aluminum T-slot with a 2" flat side dirt cheap. It would even look cool just bare without a fixture.
> 
> http://www.amazon.com/80-25-5013-T-SLOTTED-EXTRUSION-1220mm/dp/B001F0LV9I


Do you guys think this bar will provide enough heat dissipation for 12 - 3W CREE LEDs?


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## Hoppy (Dec 24, 2005)

speedie408 said:


> Do you guys think this bar will provide enough heat dissipation for 12 - 3W CREE LEDs?


That depends on what current you use. I suspect it would be fine for 700 mAmps, but might be iffy for more current. I don't think you need to run more than 700 mA if you are using the Cree XM-L LEDs - those are super bright.


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## speedie408 (Jan 15, 2009)

Hoppy,

I was planning to get the XP-Gs. Should I add a few bux to get the XM-Ls? Are they really worth the added price? 

My plan is to do 24 LEDs over my ADA 120-P. How many mA should I be running my LEDs?


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## redfishsc (Aug 29, 2010)

speedie408 said:


> Hoppy,
> 
> I was planning to get the XP-Gs. Should I add a few bux to get the XM-Ls? Are they really worth the added price?
> 
> My plan is to do 24 LEDs over my ADA 120-P. How many mA should I be running my LEDs?




The XML is a good bit more efficient than the XPG, but both will work just fine. 

I use mostly XPG myself. They are about half the price and still one of the most efficient LEDs you can get. You will be fine with either one. 

If you are only doing 24 LEDs over a 120g tank, you need to plan on running them at least at 700mA. I assume the ADA tank is a 48X24 footprint. You will want to use at least 3 of those bars for heatsinks and put 8 LEDs on each. Or you can do 4 bars, 6 LEDs. 

Do your final check with a PAR meter though unless you can find someone with a similar tank build and LED arrangement that has PAR numbers you can use to predict yours.


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## aman74 (Feb 19, 2007)

speedie408 said:


> Subscribed for future LED endeavors. VERY informative and exactly what I was looking for.
> 
> Can someone explain about "drivers" and what types are available along with the type of LEDs available and where to buy them? I keep hearing "dimmable" but how does one install such a device?
> 
> *edit* sorry for the HIJACK... maybe someone can just link me to another thread that's relevant to my questions?


I hear ya there. I feel I'm perfectly capable of doing this, yet it's still intimidating trying to get started, source parts, etc... I need things a little more paint by numbers 

The DIY LED sticky is quite old and doesn't have the pics in the OP anymore. Lots of info to be found via google, but the info is quite spread out and needs to be pieced together.

I just found another thread talking about programming a microcontroller for the fancy light cycles you seen on the crazy expensive units. Way cool stuff that some DIY folks are doing.



reybie said:


> This one is a good primer.


Thanks, that's a good overview.

A couple basic questions. Say I were to do a fixture for a 4 foot long rack with tanks about the depth of a standard 15. Modest light needs, but with some headroom for future needs. What would the cost be for a good price/performance ratio unit?

What do you see as the advantages over T5? I see them as cost in electricity and bulb replacement savings along with more flexibility in lighting levels and options. However, I saw one post saying that LED's were inefficient as they throw off a lot of heat. I'm guessing this poster was mistaken and was accounting for the equivalent lighting levels achieved with LED's, as I thought the whole thing with them was the fact that they were more efficient.

One more thing. When you arrange them so that you don't get too much spotlighting, do you still get the cool ripple effects? I see that as another potential plus as I think it looks really nice with the MH setups I've seen.


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## Dragonfish (Apr 28, 2011)

I hope this helps, here is my first build for my 38 gallon reef tank. Lots of pics and info! You can see, most people really over estimate their need for a heatsink. Mine is small and it never gets too hot. It is activly cooled but the heatsink I posted above has so much more thermal mass that it won't need active cooling for 24 LEDs running around 700ma. You can actually help it by painting it flat black. It will radiate heat more efficiently than leaving it bare metal. 

http://www.nano-reef.com/forums/index.php?showtopic=253794


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## reybie (Jun 7, 2007)

That's a nice fixture Dragonfish, especially that heatsink


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## reybie (Jun 7, 2007)

aman74 said:


> I just found another thread talking about programming a microcontroller for the fancy light cycles you seen on the crazy expensive units. Way cool stuff that some DIY folks are doing.


I probably read the same thread you were looking at and I was curious to give it a try. The only thing holding me back right now is the investment of time and materials to get started. Yesterday, I saw this controller again after reading about it in the nanoreef forums I think. For $70+, it might do the trick if I wanted to do the sunrise/sunset deal and to control moonlights and fans. Anyways, that's one more thing to think about.




aman74 said:


> What do you see as the advantages over T5? I see them as cost in electricity and bulb replacement savings along with more flexibility in lighting levels and options.


Right now, the advantage for me is cost of bulb replacement and possibly electricity savings. I still need to run it through one of those Kill-a-watt thing and see what the numbers are.

My next project is to replace the internals of my current T5 light fixture with a couple of bars of LEDs. I'm just waiting for a hanging kit to see if the current LED fixture I have gives sufficient coverage over my tank. If it does, I might not even bother retrofitting my existing T5 fixture.


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## IWANNAGOFAST (Jan 14, 2008)

I have the dim4 controller from ledgroupbuy. It's pretty slick (not looks wise but feature wise). You can run up to 12 LEDs off it without extra drivers for nano tanks, with optics, you hit a very nice par.

On my fixture, I'm doing 9 LEDs, 3 coolwhite, 3 warm white, 3 royal blue, and the 4th channel runs the fan. 

The only thing I'm not super happy about on the dim4 is when you set the max intensity of the LEDs, you do it by percentage, so instead of setting it to 500ma or 300ma, you do it at 100% (for 500ma, and 60% for 300)


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## reybie (Jun 7, 2007)

No extra drivers needed??? That would be big savings if I will not need to buy 2 drivers @ $34 each! Hmm, 2 rows of 12, 3 moonlights and a fan. Sounds like a good solution.

Edit: IWANNAGOFAST, is there an override if you want lights on for some reason or another?


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## Marko_Sp (Jun 5, 2010)

I have been looking around and find this http://http://mali-sp.si/aluminum-heat-sinks/large-heat-sinks/hr-45.html. Sending from America to Europa would cost a fortune.
I want to took two of them, long 150 cm and each is about 50 euro. Unfortunately they can not anodise such long heatsink.


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## IWANNAGOFAST (Jan 14, 2008)

reybie said:


> No extra drivers needed??? That would be big savings if I will not need to buy 2 drivers @ $34 each! Hmm, 2 rows of 12, 3 moonlights and a fan. Sounds like a good solution.
> 
> Edit: IWANNAGOFAST, is there an override if you want lights on for some reason or another?


Well, you can't do 2 rows of 12, you can only do 12 LEDs. there's 4 channels, each channel can run 3 LEDs, or a fan, or a driver. 

for that set up that you want to do, you'd need like, 2 of these dim4 things, and poof, there goes your savings.

The light I have this on is running 9 LEDs, 3 cool white, 3 warm white, 3 royal blue, and a fan.


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## reybie (Jun 7, 2007)

Oh man, I totally screwed that up. I thought it could do 12 max per chan with a min of 3!!


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## trackhazard (Aug 24, 2006)

My wife is using a heatsink for her refugium sourced from somewhere (cant remember if it was rapidled or heatsinkusa) but it was a leftover and had a bunch of marks on it so she got it for real cheap.

For her tank fixture, she made a frame made out of L channel aluminum and screwed the corners together with the bottoms of the L's facing inwards, creating a little lip. She then attached her LEDs with thermal paste to aluminum C-channel that drops right into the frame. The plan is to not permanently attach them so the she has some leeway to adjust lighting by sliding individual c-channels so she can get light where she wants it and/or remove c-channels as she sees fit.

She is planning to use active cooling on the C-channels to keep things cool.

http://www.reefcentral.com/forums/showthread.php?t=2030311

-Charlie


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## majstor76 (Jun 11, 2010)

Ive done some LED lights and used piece of aluminium for heatsink










10*3W of leds , 1 m long aluminium

Temperature goes to 45C


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## IWANNAGOFAST (Jan 14, 2008)

Trackhazard, your wife's tank is awesome!!


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## reybie (Jun 7, 2007)

majstor76 said:


> Ive done some LED lights and used piece of aluminium for heatsink
> 
> 10*3W of leds , 1 m long aluminium
> 
> Temperature goes to 45C


Have you added any kind of cooling?


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## audioaficionado (Apr 19, 2011)

IWANNAGOFAST said:


> Well, you can't do 2 rows of 12, you can only do 12 LEDs. there's 4 channels, each channel can run 3 LEDs, or a fan, or a driver.
> 
> for that set up that you want to do, you'd need like, 2 of these dim4 things, and poof, there goes your savings.
> 
> The light I have this on is running 9 LEDs, 3 cool white, 3 warm white, 3 royal blue, and a fan.


You can run multiple series strings in parallel as the current will split to each branch based on Ohm's law and the driver's current limiting function. The strings will each have to have the same number of identical LEDs so they all see the same forward voltage drops.


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## majstor76 (Jun 11, 2010)

reybie said:


> Have you added any kind of cooling?


No, no cooling, im ready to exchange LED life expectancy for silence
*http://www.expectancy.co.uk/*


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## redfishsc (Aug 29, 2010)

majstor76 said:


> No, no cooling, im ready to exchange LED life expectancy for silence




My first thought was "just use a nice quiet computer fan" but then the sound of my own "nice quiet computer fan" buzzing behind me on my aquarium reminded me.... they ain't always quiet lol. 

On a larger array where silence is required, there are some very quiet computer fans that can be used (not much is really needed!). Better to buy a costly computer fan for $20-30 than cook $50-100 in LEDs.


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## jcgd (Feb 18, 2004)

How about an old aluminum extension ladder? You cut use the rails, not the steps, for heatsinking material. Sometimes you can find 20' ladder for $20 bucks or so.


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## majstor76 (Jun 11, 2010)

redfishsc said:


> On a larger array where silence is required, there are some very quiet computer fans that can be used (not much is really needed!). Better to buy a costly computer fan for $20-30 than cook $50-100 in LEDs.


Sure, nice humid-proof and silent vents can be found but in my case is not really needed since my LED-a are paid only 20$ and its not a disaster if they croak. But i dont expect them to, humidity and water splashing is bigger problem, me thinks.


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## silvawispa (Oct 11, 2011)

I'm new here, and I'm waiting for my XM-L's to arrive from deal extreme, my experience level is zero, but here's my DIY cooling plan....

I want a single slim bar hung over the length of the tank with shade/reflectors coming out to each side.

The 1 1/8" square cooling bar I plan to use fits in the slot with LEDS mounted to it. The bottom of the reflector is drilled and is to be fitted with 'windows' for each LED. Wiring is kept out of sight and dry between the bar and the reflector. The reflector will hang over the tank.

reflector design:









Here's my take on cooling, air cooled heat sink is expensive. £100 for the 6ft recessed piece I first wanted (this would have allowed me to put a splash guard in neatly and would have looked awesome.)

I have a tank of 150+ gallons of water at 25C. I run pumps to move the water around. It's not going to take too much work to rig up a watercooled system. My main eheim filter is more than capable of doing the water lifting and flow required, a couple of their tap fittings will make maintenance a doddle. It's not that hard to put it all together....

Square aluminium tube is cheap. I bought the piece I need for £20 (actually there was a screw up so I have 3 of them. Damn  ) Since it's a standard size,end caps to silicone securely in place are readily available, these will be drilled and fitted with tubing compatible with my filter.

I am planning on building a test rig of 10 XM-L crees running at 3A from a simple driver. 

A 100 watts of power into my lights. 10,000 marketing lumens. Woohoo!

Electronics are going to be boxed and air-cooled under the tank.

Can anyone see any major glaring OOOPSes of F-ups waiting to happen that I've missed?

Other aims: Not to poison the fish with aluminium! The inside of the tube will be painted with acrylic and left to cure.
To be able to switch out the LEDS to experiment with different colour combinations.
To upgrade the drivers to dimmable versions as time, expertise and money become available.

I know of another watercooled DIY rig in germany, anyone know of any others that have been built or in the design stage?

Money already spent: 
10 XML's+driver £65
5m of 1 1/8" Aluminum square tube £20
various aquarium fittings and silicone sealant: one bucket of plants to LFS 

Money needed to spend: 
£30 on sheet mirror finish alu 2000x500mm.
£15 project box to house electronics.
£10 miscelaneous bits of wire/solder etc.
Total £120.

I'm hoping this complete unit will set me back about £120 in total, not that much more than the the cost of replacing the 300W of T5 tubes I'm running now! Not bad since the projected lifespan will be 8-14 years as opposed to 12-18 months...

So if it works out, I'll replace one of my luminaires this year and build the other one as the other half of the T5's wear out. (and LED prices drop  )
Paul Silver.

PS I'll post my own build thread in the next couple of weeks, once everything has arrived.


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## redfishsc (Aug 29, 2010)

Very interesting idea, Silvawispa. 

At first I thought you were smoking crack using 0.5mm thick aluminum as a heatsink for XML's (or really any high power LED), but then I realized you were talking about a water cooled system, which is a whole nuther animal . 


Regarding using acrylic/epoxy to coat the inside of the aluminum tube, I think you're going to spend more money on getting a reliable coating than it's worth... unless you work somewhere that will do this for you for free. Water will eventually gnaw at most of the commonly available coatings we have at our disposal--- I wouldn't trust any of them. 



I think you'd be better of with a heat exchange system of some sort--- use a closed loop system (where the coolant water never actually mixes with tank water) and make a DIY "radiator grill" to exchange the heat into your tank. That would also be a crazy design but I can't see any reason it wouldn't work. 

FWIW, in the end, I think it would be much easier to find a dozen or two scrapped CPU heatsinks and mount 1-3 Cree XML's on each one lol .


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## Hoppy (Dec 24, 2005)

You could put a very small fan on each end of that square tube, so one blows in and one blows out. That would air cool it very well, and that's all the cooling you really need. I wouldn't even consider using water to cool a LED array - just keeping the water inside the tube and not on the electric circuit or the LEDs would be a challenge. And, electricity plus water equals rapid erosion of metals.

Another idea would be using thicker wall square tubing, with thicker aluminum sheet for the "shade". Then all of the aluminum would act as a good heatsink. With that you might not even need fans.


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## jcgd (Feb 18, 2004)

redfishsc said:


> I think you'd be better of with a heat exchange system of some sort--- use a closed loop system (where the coolant water never actually mixes with tank water) and make a DIY "radiator grill" to exchange the heat into your tank. That would also be a crazy design but I can't see any reason it wouldn't work.
> 
> FWIW, in the end, I think it would be much easier to find a dozen or two scrapped CPU heatsinks and mount 1-3 Cree XML's on each one lol .


I agree with a radiator type system. But I'm not sure what kind of pipe would be safer than aluminum to run aquarium water through. I also think running 10 XML at 3A will put a lot of heat into the aquarium. At three amps, they will be really hot; hell, without a quality heatsink and lots of air movement they would be tough to keep cool. By this I don't mean that method would be better than water cooled. I'm just trying to illustrate how warm they will be. Mine running at 2000mA, 7 on a 12x6" heatsink, passively cooled was about the threshold for being able to keep my hand on it. I'm not sure exactly how much the heat could warm your tank, but it might be a bit much.

Is the reflector just for looks? As far as use for reflecting light, very little, to no light at all will be reflected. The spread of the LEDs just wont hit it.

One row of LEDs might not be great coverage, front to back. I'm interested to see how it would look over a larger tank.

Edit: I agree with Hoppy about not doing a water system, but my advice was if you are doing it anyway. I also think you want some decently thick stock if you go with air cooled.


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## silvawispa (Oct 11, 2011)

Interesting thoughts, thanks.

First up, I'm going to do it anyway, partly because I can and partly because I like the idea of recycling the heat back into the tank. Right now I'm paying to heat the tank all the time anyway. (I have 2x 300W heaters in there, although one is redundant, set at a lower temp to cover me for a failure.) So I'm not worried about the scraps left over from a 100W light over-heating the tank. I'm actually more concerned over the radiant cooling when the light is off/at low power costing me more to heat the tank! I'm thinking a nice 'ipod white' finish will look pretty sharp and not lead to me slapping insulation on it! (as was done in the other example I've seen)
Remember I'm in the UK and the room temp never goes above 20C, and over the winter will normally be 10-16C. I'd rather wear more clothes than pay for heating.

As to keeping electricity away from the water I already have 3 mains cables running INTO my tank and THIS is considered normal! (2x heaters, one powerhead/filter)

What I propose with the cooling tube, puts solid aluminium, with the only holes at the ends sealed to inlet and outlet pipes with fairly low pressures in them, between the water and the power. The power for the lights will come into the system in the middle of the fitting as far away from potential leaks as possible, also the electrics will be reasonably well sealed by the design, and I'll be very focused on keeping the power in the right place. (it's DC, at least so I shouldn't have any induction issues to come up against. Hopefully!) Whilst I might not feel 100% confident in dunking the fitting, I would be absolutely happy that a leak in the cooling system will give me no electrical problems.

As to painting the inside of the tube, yes it's a pig, and overkill to boot for a freshwater system. I want the experience of running it though, in case I need to put together a salt water variation where bare aluminium becomes more of an issue, especially when mixed with electricity. Stainless steel water cooler pipe anyone? 
Is a repaint every few years harder than paying for new tubes? 

Maintenance free lights would be the grail, but is it realistic?
(hmm, stainless pipe........)

The reflector is partly due to having a glass toppped tank, (siamese algae eaters just love to jump, and my son startled one of my angels onto the carpet one maintenance day. The poor dear was covered in glitter for a while...) So whilst it won't gain me that much light into the tank, it will stop an awful lot of reflected spill.Yes, it would be awesome to have this over a rimless without a reflector, the shimmer on the walls would be purrrdy 
Another thought would be that I could close down the angle of the reflector to reduce the spill to zero. Experiments to be done...fun to be had...

As to spread, this unit is only designed to cover half the width of my tank, 12", so if I mount it so that the minimum relative light intensity hitting the tank is about 2/3rds of full intensity (about a 50º angle* according to tests sourced dubiously on the internet...) I should have a decent spread. In plain terms, 12-15" above the waterline should be good 

If I get good plant growth with this unit, I will build a second, possibly testing Hoppys air cooled fan idea, to get the full tank coverage. I'll also be looking at putting a dimmable system in at that point.

A question on optics, do the optics simply transfer the spread pattern into a smaller angle, or are they available so that they smooth out the curve so the light is a more uniform intensity across the spread? A uniform spread optic would be helpful in terms of efficiency.

Closed loop systems. I think I'll leave that for my computer. I don't think the added complexity is worth the bother.

Redfish, it would work, and work well, but you'd have to hide it in a box, because pretty it won't be!

Hmmm, I have fans and the tube, Hoppy, how much faith do you have in an air cooled tube shifting enough heat from a set of 10W XM-L's running at full whack? If anyone has the test gear for me to borrow I'd be prepared to run some temperature tests on active air cooled tube heatsinks. (and of course the watercooled version!) At least we'd have data then.
Also thoughts of longevity come to mind, would dust build up be an issue?

Paul.

*fun fact, hold alt and type 0186 on the number PAD (not the number row), for the degree 'º' symbol


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## WingoAgency (Jan 10, 2006)

I believe this heat sink/fixture with splash guard solve a lot of your issue regarding DIY looks.







[/url] Flickr 上 WingoAgency 的 Revolution LED Beta[/IMG]







[/url] Flickr 上 WingoAgency 的 Revolution LED Bar[/IMG]


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## reybie (Jun 7, 2007)

I like the stands you created for the fixture. Very slick!


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## redfishsc (Aug 29, 2010)

Very nice heatsink Wingo, nice work indeed.


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## Hoppy (Dec 24, 2005)

silvawispa said:


> A question on optics, do the optics simply transfer the spread pattern into a smaller angle, or are they available so that they smooth out the curve so the light is a more uniform intensity across the spread? A uniform spread optic would be helpful in terms of efficiency.


From the testing I have done I don't believe the optics do any significant smoothing out of the intensity. The intensity from a bare Cree LED is reasonably smooth anyway.


> Hmmm, I have fans and the tube, Hoppy, how much faith do you have in an air cooled tube shifting enough heat from a set of 10W XM-L's running at full whack? If anyone has the test gear for me to borrow I'd be prepared to run some temperature tests on active air cooled tube heatsinks. (and of course the watercooled version!) At least we'd have data then.
> Also thoughts of longevity come to mind, would dust build up be an issue?
> 
> Paul.


I wouldn't dream of using XM-L LEDs at 3 amps, without using a very good cooling method, so I doubt that a hollow aluminum tube with a fan at each end would be adequate at that power. But, that is just an emotional reaction, not based on any experience at that current. I don't see much benefit to going beyond about 1.5 amps on those anyway. They would produce so much PAR that the light would need to be 3 feet and more from the substrate to avoid having too much PAR, and/or to avoid having very uneven light intensity.

Longevity for a LED light is, in my opinion, totally unknown. Cree XM-L LEDs have been in use for far too short a time for anyone to even guess at how long they will work, and how much they will deteriorate over time. Since most of us want something newer and better about every 2-3 years anyway, a longer life that that isn't necessarily a good thing.


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## silvawispa (Oct 11, 2011)

How much PAR is too much, and for which species does that apply? 
Is there a useful discussion somewhere that I've missed?

XM-L's have been brutalised at silly voltages and currents on the flashlight forums, at least 50% over rating, not that they put out any more light, they just seem to survive. So I suspect they will last a long time!


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## audioaficionado (Apr 19, 2011)

I imagine that if you run quality LEDs at half or less of their rated current, the longevity extension will be more exponential rather than linear.


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## silvawispa (Oct 11, 2011)

audioaficionado said:


> I imagine that if you run quality LEDs at half or less of their rated current, the longevity extension will be more exponential rather than linear.


The failure time when over driven is certainly exponential, down to milli seconds at 5 Amps+ apparently...

However I see no point in limiting these things just so that they will outlive my grandchildren! If they're burning my plants, that's a different thing!

Longevity is mainly linked to operating temperature, which brings us neatly back to the topic at hand. 

I'm jealous of those heatsink prices from 80/20 on amazon US, that were linked to a few pages back, that company had other sinks that looked better too (and could be wired for liquid  )

I doubt I'd be looking at watercooling if those sinks were available to me.

Great looking set-ups Wingo, a little bit light weight for my 6ft tank though!


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## jcgd (Feb 18, 2004)

I've heard of XML running at 6000mA with serious cooling going on. Not saying I would do it, but as long as the junction is kept cool the circuitry will be your limiter. I'm also not saying the circuitry will last a 6000mA, but if you keep the junction sufficiently cool while running at 3A is should last about as long as if you seriously under power it.


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## silvawispa (Oct 11, 2011)

I read that one too, and some other threads where the LED blew at 5A instantly.
I'm putting it down to manufacturing tolerance.
The other notable result is that they produce less light after they get to 3.5A, mine will be at 2.8A, so I have margin for error.
And yes I'm hoping the lifespan at my chosen running parameters will be measured in decades


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## jcgd (Feb 18, 2004)

Yeah, it seems there isn't much point in going too high on the current as the light output drops to unimpressive levels. 

I'm interested to see how your design turns out. Haven't seen anything like it yet nor even similar really.


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## silvawispa (Oct 11, 2011)

watercooled diy led rig

if you just see a loading icon, scroll down a bit.

I want mine to look a lot better than this, but the principle is the same.


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## reybie (Jun 7, 2007)

Very interesting...


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## audioaficionado (Apr 19, 2011)

I'd just double up on the LEDs and then they will cover better and run cooler for much longer. Dim them even further as needed. They aren't that expensive overall if you factor in all the rest of the components and the time and effort to design and build it.


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## silvawispa (Oct 11, 2011)

It's over half the cost of this build and if I factor in dimmable drivers and controllers it would comfortably double, possibly triple the build price. I'm not putting that money out until I'm happy my tank is happy.

There is another point that I suspect, and wish to confirm, fewer and higher intensity light sources might be better for plant growth. (In it's most simplistic form, there is only one sun.)

P


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## WingoAgency (Jan 10, 2006)

Reasonable assumption *BUT UNFORTUNATELY NOT FACTUAL!*

If you read thru this article
http://www.cree.com/products/pdf/XLamp-Pulsed-Current.pdf
you can see that before thermal runaway happens the LED diode degradation is negligible. 

Thermal runaway can be caused by over current or seriously under thermal management. In another word, the life expectancy of LED is more or less the same when run within spec. However, when they are run over the spec, too hot, too much current ..., they die in an exponential speed.



audioaficionado said:


> I imagine that if you run quality LEDs at half
> or less of their rated current, the longevity extension will be more exponential rather than linear.


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## audioaficionado (Apr 19, 2011)

silvawispa said:


> It's over half the cost of this build and if I factor in dimmable drivers and controllers it would comfortably double, possibly triple the build price. I'm not putting that money out until I'm happy my tank is happy.
> 
> There is another point that I suspect, and wish to confirm, fewer and higher intensity light sources might be better for plant growth. (In it's most simplistic form, there is only one sun.)
> 
> P


You can run 2 strings of LEDs series-parallel on one driver. The current divides between the strings and the LEDs run on half the current. So all you need is more LED's. So it's not double the total cost. Maybe 35-50% more total.


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## silvawispa (Oct 11, 2011)

@wingo:That data sheet is for over driven pulsed current, not what we are using here.

Lifetime probably is exponential to current drop. After all at zero current, lifespan is unlimited. (Datasheet http://www.cree.com/products/pdf/xlampxm-l.pdf )

@audio, true, but I already went over my 'similar cost to new T5's' budget...


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## WingoAgency (Jan 10, 2006)

For those who plan on using the XML or another other ultra power leds 10W, 30W.... cooling is priority no.one. 3 years ago, my first 2 3 prototypes of 30W start to malfunction after only about 9 months of operations even though I use PC heatsink fan combo. When the rectangular shaped 30W came out, none of my built failed uptil now(3 years). The compound I used are same and the heat sink/fan combo are basically all same. The form factor that they come in a BIG rectangle rather than a small oval helps the initial transfer of the heat from the matrix especially I am using only the cheaper ceramic heat paste not arctic silver. The package of XML is very small compare to other companies' ultra power led and thus the contact, the heat paste and such must be done right in order to have the heat transfer out properly.


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## WingoAgency (Jan 10, 2006)

silvawispa said:


> @wingo:That data sheet is for over driven pulsed current, not what we are using here.
> 
> Lifetime probably is exponential to current drop. After all at zero current, lifespan is unlimited. (Datasheet http://www.cree.com/products/pdf/xlampxm-l.pdf )



Correct the chart is for over current but it explains why a LED failed. It explains that before a threshold is reached, the failing events will not happen(or better to say negligible.) Similarly, your proposed scenario at zero current, it's a threshold, a threshold that can be described as BEFORE THERE IS ANY CURRENT, NOTHING WILL HAPPEN. Conversely we cannot assume the negative values of current will be exponentially or inverse exponentially affect the LED.

Let's think of it as water, water vapor and ice before the threhold is reached the property observed in one phase cannot be directly applied to other phases. When temperature of water reaches a threhold it expands to gas form and when temperature reaches the other threhold it expands again but much slower in form of ice.


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## silvawispa (Oct 11, 2011)

Yes I can see that a failing LED is in a different state to a normally working one. The over driven current document was all about LED's in failing states. That isn't the state we are discussing.

An LED running at a higher temp/power will suffer more electron migration and 'normal wear' than one running at a lower power/temp, this is the degradation that comes into play when talking about normal lifespan.

For example, if I put 0.1W through the XML it will produce a little light, a tiny amount of heat and very little electron migration, when will it fail? I suspect it's lifespan will be many times greater than the same XML with 1W running through it, and again an XML with 10W will degrade quicker still (@ 3A, @50K hrs it should still run at 70% brightness, that's 17 years of 8hrs/day...) So I don't think this really merits any worry, so long as we keep 'em cool!


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## redfishsc (Aug 29, 2010)

audioaficionado said:


> You can run 2 strings of LEDs series-parallel on one driver. The current divides between the strings and the LEDs run on half the current. So all you need is more LED's. So it's not double the total cost. Maybe 35-50% more total.


I recommend against this. If you blow a single LED that dies as a closed circuit (meaning, the other LEDs stay on) then you now suddenly have mis-matched parallel strings, and thus the string that is missing an LED will be getting a higher voltage. Theoretically this can cause a cascade effect. 


Lots of people do it, don't get me wrong, but I'd be cautious about it myself.


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## redfishsc (Aug 29, 2010)

WingoAgency said:


> For those who plan on using the XML or another other ultra power leds 10W, 30W.... cooling is priority no.one. 3 years ago, my first 2 3 prototypes of 30W start to malfunction after only about 9 months of operations even though I use PC heatsink fan combo. When the rectangular shaped 30W came out, none of my built failed uptil now(3 years). The compound I used are same and the heat sink/fan combo are basically all same. The form factor that they come in a BIG rectangle rather than a small oval helps the initial transfer of the heat from the matrix especially I am using only the cheaper ceramic heat paste not arctic silver. The package of XML is very small compare to other companies' ultra power led and thus the contact, the heat paste and such must be done right in order to have the heat transfer out properly.




I just quoted this so that people would see it TWICE. I LOVE cheap heatsinks but I do NOT like anemic heatsinks. Put some beef under your LED's if you are running them any higher than 700mA. 

I can attest that a single Cree XML at 3,000mA will heat up like a little phosphorus grenade!!!!!


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## audioaficionado (Apr 19, 2011)

redfishsc said:


> I recommend against this. If you blow a single LED that dies as a closed circuit (meaning, the other LEDs stay on) then you now suddenly have mis-matched parallel strings, and thus the string that is missing an LED will be getting a higher voltage. Theoretically this can cause a cascade effect.
> 
> 
> Lots of people do it, don't get me wrong, but I'd be cautious about it myself.


Won't hurt a thing as they are each running half the max current. Worst scenario is that the string getting most of the current will still be under rated max. The shorted LED will be dark and the rest slightly brighter than the other string.


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## redfishsc (Aug 29, 2010)

audioaficionado said:


> Won't hurt a thing as they are each running half the max current. Worst scenario is that the string getting most of the current will still be under rated max. The shorted LED will be dark and the rest slightly brighter than the other string.


It's not the current that bothers me, it's the voltage increase. 

Are you saying the voltage increase (on the side with the dead LED) would cause that string to draw more current than the other side, with all working LEDs?


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## Hoppy (Dec 24, 2005)

redfishsc said:


> I recommend against this. If you blow a single LED that dies as a closed circuit (meaning, the other LEDs stay on) then you now suddenly have mis-matched parallel strings, and thus the string that is missing an LED will be getting a higher voltage. Theoretically this can cause a cascade effect.
> 
> 
> Lots of people do it, don't get me wrong, but I'd be cautious about it myself.


With 2 parallel strings of 10 LEDs, for example, driven by one LED driver, if one LED fails open circuit, which is the usual failure mode, the other string gets twice as much current, and the failed string gets no current at all. The voltage applied to each string stays the same. So, as long as you are running the 2 strings at half or less of their rated current, you should see no cascade of failures. If you have 4 parallel strings, the current in the 3 remaining strings increases by only 33%, still no problem.

A LED can possibly fail by shorting across the contacts. In that case the other string can possibly stop working because the voltage produced by the driver will be too little to drive the un-failed string, but no cascade should occur then either. The LED driver may fail if it has to run at too low a voltage.

I think I'm correct on this, but I may not be.


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## audioaficionado (Apr 19, 2011)

The driver is current limited. It won't over current as it adjusts the output voltage to keep the current the same. If a string of series LEDs has one open up, the whole string will go dark as no current can flow through the others. If one LED shorts, the rest of the LEDs in that string will each get more voltage as the voltage drop on the shorted LED gets redistributed over the rest.

Two series-parallel strings will split the current between them as the driver won't allow any more current to flow. Now if one LED in one string opens up, that string will go dark and all the avaiable current will go through the remaining string which will then get brighter as more current will flow through it and the power will also go up as Watts = Voltage x amps. More current with same voltage drops per LED.

Now if one LED shorts, that string will have less resistance and each remaining LED will get brighter as more current will flow through that string as it now has less resistance. That will take some of the current load away from the fully functioning string that has a slightly higher resistance. So the shorted string will have slightly brighter LEDs and the other string will get a little dimer. No cascading failure possible as long as no LEDs are over current.

We're talking about long strings of several LEDs each and not just a few.


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## WingoAgency (Jan 10, 2006)

redfishsc said:


> I just quoted this so that people would see it TWICE. I LOVE cheap heatsinks but I do NOT like anemic heatsinks. Put some beef under your LED's if you are running them any higher than 700mA.
> 
> I can attest that a single Cree XML at 3,000mA will heat up like a little phosphorus grenade!!!!!


Yup, the the total mass of the heat sink does matter. In fact, I have prepared a chart on what maximum LED wattage that heat sink can take per length before active cooling is needed. As long as heat sink / LED watt is within spec then the temperature will stay save. If one bar is not enough for the total LED required, go for more bars(or pcs of heat sinks) instead of cramping then in one. I made a PCB basically spaced out properly for the heat sink. However, if I ever use more powerful LEDs or denser configuration, then I use this much bigger heat sink. 







[/url] Flickr 上 WingoAgency 的 Mounting Revolution Strips Ideas 1024[/IMG]

And in reef applications, they often requires active cooling along with multiple strips.


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## silvawispa (Oct 11, 2011)

deleted


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## WingoAgency (Jan 10, 2006)

Lol, I was thinking for a moment what is that reply about with all the car stuff popping up.


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## jcgd (Feb 18, 2004)

redfishsc said:


> I recommend against this. If you blow a single LED that dies as a closed circuit (meaning, the other LEDs stay on) then you now suddenly have mis-matched parallel strings, and thus the string that is missing an LED will be getting a higher voltage. Theoretically this can cause a cascade effect.
> 
> 
> Lots of people do it, don't get me wrong, but I'd be cautious about it myself.


If you have proper safeguards in place, ie. Fuses, you don't need to worry.


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## redfishsc (Aug 29, 2010)

audioaficionado said:


> Now if one LED shorts, that string will have less resistance and each remaining LED will get brighter as more current will flow through that string as it now has less resistance. That will take some of the current load away from the fully functioning string that has a slightly higher resistance. So the shorted string will have slightly brighter LEDs and the other string will get a little dimer. No cascading failure possible as long as no LEDs are over current.
> 
> We're talking about long strings of several LEDs each and not just a few.


How many 3-watt type LEDs per string are you recommending for a minimum, when using parallel strings?


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## audioaficionado (Apr 19, 2011)

Depends on the driver's maximum voltage. I'm thinking 10 or more.


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## Hoppy (Dec 24, 2005)

audioaficionado said:


> The driver is current limited.


The driver isn't current limited - instead it produces a constant current. If it is set to produce 1 amp, that is what it produces, whatever happens with the load. (within some limits)


> It won't over current as it adjusts the output voltage to keep the current the same. If a string of series LEDs has one open up, the whole string will go dark as no current can flow through the others. If one LED shorts, the rest of the LEDs in that string will each get more voltage as the voltage drop on the shorted LED gets redistributed over the rest.


Nope! The total voltage drop across the string will continue to be the forward voltage drop of each LED times the number of LEDs still operating. This will be less than the voltage drop across the parallel string(s). Since the total current from the driver will still be constant, the only thing the driver can do is drop its output voltage until the current is at that value. But, that will be the voltage drop across the string with the shorted LED, so it will be too little voltage to drive the other string at anything but a very low current (forward voltage drops as current drops). This will mean the string with the shorted LED will operate at more than half the total driver output current, but for 2 parallel strings, the current will never be more than twice what it was operating at. The problem would be with 3 or more parallel strings, where the string with the shorted LED could end up with the total driver current, which could be beyond the LED's capability.


> Two series-parallel strings will split the current between them as the driver won't allow any more current to flow. Now if one LED in one string opens up, that string will go dark and all the available current will go through the remaining string which will then get brighter as more current will flow through it and the power will also go up as Watts = Voltage x amps. More current with same voltage drops per LED.
> 
> Now if one LED shorts, that string will have less resistance and each remaining LED will get brighter as more current will flow through that string as it now has less resistance.


 It isn't that there is less resistance, it is that the total of the forward voltages goes down due to less LEDs operating, but offset by the forward voltage per LED going up from the higher current.


> That will take some of the current load away from the fully functioning string that has a slightly higher resistance.


 Not resistance, total of the forward voltages.


> So the shorted string will have slightly brighter LEDs and the other string will get a little dimer. No cascading failure possible as long as no LEDs are over current.
> 
> We're talking about long strings of several LEDs each and not just a few.


I find it hard to think in terms of how LEDs operate, and forget all about V=IR circuits, but we have to or we run into possible problems.


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## WingoAgency (Jan 10, 2006)

Hoppy said:


> I find it hard to think in terms of how LEDs operate, and forget all about V=IR circuits, but we have to or we run into possible problems.




+1 
In thinking how LED circuit works, forget about V=IR, start off with forward voltage and forward current.


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## Surgeon (Jun 17, 2011)

redfishsc said:


> There is no real reason you couldn't use multiple CPU heatsinks over a large tank as long as you don't overwork them by using too many LEDs and high drive currents.


CPU heatsinks are designed to handle an awful lot of heat (as long as theres a fan). I'd be suprised if any LED produces as much heat.


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## redfishsc (Aug 29, 2010)

Surgeon said:


> CPU heatsinks are designed to handle an awful lot of heat (as long as theres a fan). I'd be suprised if any LED produces as much heat.


Oh there are plenty, I've seen them up to 300 watts. They're despicably inefficient, but they are around. Some of the heatsinks you can buy for them are water cooled. 

CPU heatsinks can often be found dirt cheap/free, which is why I suggested them (ie, the topic of this thread)


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## WingoAgency (Jan 10, 2006)

redfishsc said:


> Oh there are plenty, I've seen them up to 300 watts. They're despicably inefficient, but they are around. Some of the heatsinks you can buy for them are water cooled.
> 
> CPU heatsinks can often be found dirt cheap/free, which is why I suggested them (ie, the topic of this thread)


Stupid me, I paid $6-8 a pcs with a fan(used) when I first did my DIY Reef LED prototype 5 years ago:iamwithst


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## redfishsc (Aug 29, 2010)

I just got two of these AWESOME heatsinks from a friend that does computer work. 

They appear to be solid copper (ie, better than aluminum!) and they have fans built onto them.


I'm going to fill one of them with Cree's and make a fishing light (night fishing) over the winter so I can do some heavy duty crappie fishing in the spring. If I can find a 12v driver that will run them at 1,000mA or more, I will .


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## audioaficionado (Apr 19, 2011)

Intel supplies Al/Cu heatsinks w/fan with their boxed CPUs. Wish I hadn't tossed the 3 I had laying around from PC builds. Should be easy to get some more online for cheap from other system builders.


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## O2surplus (Jan 31, 2010)

I used CPU heat sinks on my last build that I found at my local electronics supplier. They were surplus items, so they only cost me about $11 each. Each unit came with it's own 12 blower style fan. I mounted 1 BridgeLux 50 watt led array to each of the six Heat sinks and have been running them for the last two months with no problems at all. The Leds came with a test connection for checking the junction temp and my measurements showed that the leds were being cooled effectively, as long as the cooling fans were functioning.


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## Naekuh (Oct 19, 2011)

audioaficionado said:


> Intel supplies Al/Cu heatsinks w/fan with their boxed CPUs. Wish I hadn't tossed the 3 I had laying around from PC builds. Should be easy to get some more online for cheap from other system builders.


yeah i had a question in regards to PC heat sinks..

The average Northbirdge Bridge heat sink... its those small ones with the fan in the middle like this:










they also come in Alu, can handle about 50W with the active fan. 

The fan itself is also 12V, so i was thinking... how much heat do the higher wattage LED's really put out?

Because i see people using full blown cpu heat sinks ratted at 150W to cool 50W LED's making me go :help: did i miss calculate the heat on a LED?

Because physics says if something draws 50W, and assume worst case scenario you get 90% of that power in heat... a north bridge sink should be enough for a 50W LED.

Or is reality cruel and playing games with me?


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## silvawispa (Oct 11, 2011)

What is your definition of higher power? My build is using 10W XM-l's as a nice compromise on efficiency vs raw lumens, with a side order of quality...

I just played with them for the first time this afternoon.
Putting 1.4W through it managed to warm it up to 30º with just the alu base plate as a heatsink. (I wasn't quite sure what was going to happen with the dubious power supply I was using so it initially started off sitting on an intel i5 cooler...)
Even allowing for the drop in efficiency at higher currents, I don't think it's going to take any where near that which I feared, to cool it, running it at 3A/10W.

I don't think you were missing anything Naekuh!


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## redfishsc (Aug 29, 2010)

Naekuh said:


> Because i see people using full blown cpu heat sinks ratted at 150W to cool 50W LED's making me go :help: did i miss calculate the heat on a LED?
> 
> Because physics says if something draws 50W, and assume worst case scenario you get 90% of that power in heat... a north bridge sink should be enough for a 50W LED.
> 
> Or is reality cruel and playing games with me?



Keep in mind that you can't compare watts to watts. Well, not CPU watts to LED watts. 

CPU's produce heat in a different proportion to their power consumption (wattage) than LEDs, and one LED brand/model varies wildly from the next also. 


Most CPU heatsinks that I've held would be OK for up to about a 50 watt LED if fan cooled. If NOT fan cooled, no more than 20 watts.


The final answer is to test it out, or test out a similar heatsink/LED combo and make an edumacated guess at how you can alter the situation. 

I judge heatsink heat in a very crude way---- if it feels "uncomfortable" to touch for more than 5-10 seconds with the back of my hand, I add a fan. If it doesn't bother me, I don't bother with a fan. Very crude and totally relative, but works for me lol.

I do have an infrared thermometer at work I have used to 'test' this out before, and I cannot remember the actual temps I got, but I do remember confirming my method as "reasonable" lol.


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## Naekuh (Oct 19, 2011)

silvawispa said:


> I don't think you were missing anything Naekuh!


yeah thank you...

i was figuring on that... i just got scared when i saw all these people bust out cpu heat sinks to cool the LED's, or would MASSIVE heat sinks...

And i was completely lost on why.. lol..


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## redfishsc (Aug 29, 2010)

Does anyone have an online, AFFORDABLE source for C-channel/U-channel for LEDs??? Something we can buy by the foot preferably?


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## Hoppy (Dec 24, 2005)

There is at least one Ebay store that sells aluminum extrusions, including channels, for what I consider not outrageous prices. I'm fortunate in having a local dealer where I get mine, at much lower prices.


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## redfishsc (Aug 29, 2010)

Hoppy said:


> There is at least one Ebay store that sells aluminum extrusions, including channels, for what I consider not outrageous prices. I'm fortunate in having a local dealer where I get mine, at much lower prices.


Maybe you should set up shop as a reseller .

I've literally thought about buying cheap throw-away CPU heatsinks from local stores to resell as LED heatsinks for smaller tanks, but I just don't see a market for it without investing a lot of time in it. I've just got so many friends who do CPU work that I get them free all the time. I'm sure I could get a LOT more if I offered a buck or two for them.


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## Hoppy (Dec 24, 2005)

redfishsc said:


> Maybe you should set up shop as a reseller .
> 
> I've literally thought about buying cheap throw-away CPU heatsinks from local stores to resell as LED heatsinks for smaller tanks, but I just don't see a market for it without investing a lot of time in it. I've just got so many friends who do CPU work that I get them free all the time. I'm sure I could get a LOT more if I offered a buck or two for them.


I did think about selling aluminum channel pieces, but that store sells surplus materials, and they rarely have the same sizes of channels for two consecutive visits. Once when I completed a design based on a big lot of a perfect size channel, when I returned to buy the material, they didn't have any even close to that size. And, I have learned over the years that I'm not a businessman.:icon_sad:


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## Dragonfish (Apr 28, 2011)

I actually bought and used the one I posted and it does a great job!


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