LED Heat Sink/Cooling - The Planted Tank Forum
 
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post #1 of 15 (permalink) Old 03-12-2009, 08:00 PM Thread Starter
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LED Heat Sink/Cooling

Would one of these, http://tinyurl.com/c6emhb work to keep a high power LED cool? I can see putting 8 of these in a 4 x 2 grid to make an aquarium light. Or is this overkill? Much too expensive?

Or, http://tinyurl.com/bd38no

Hoppy
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post #2 of 15 (permalink) Old 03-12-2009, 08:13 PM
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Quote:
Originally Posted by Hoppy View Post
Would one of these, http://tinyurl.com/c6emhb work to keep a high power LED cool? I can see putting 8 of these in a 4 x 2 grid to make an aquarium light. Or is this overkill? Much too expensive?

Or, http://tinyurl.com/bd38no
Something like this would be more appropriate (and a lot cheaper).
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post #3 of 15 (permalink) Old 03-12-2009, 08:42 PM Thread Starter
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Thanks Dalban, I couldn't find those when I looked. But, wouldn't you love to listen to 8 of those little fans all running at once?

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post #4 of 15 (permalink) Old 03-13-2009, 02:31 AM
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Even better to go to heatsinkusa.com. Buy it cut to lenght and in 5+'' or 8+'' wide. I can't remember the exact widths. Heavy duty alumin in one pc. Then buy a 120mm fan or two and use them to cool it. I have a 12''L x 5+''W heatsink with two 120mm fans to cool it. One fan is enough but I like redundancy. I am using 12 Cree 3W LEDs in my build.
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post #5 of 15 (permalink) Old 03-13-2009, 02:36 AM
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Hoppy,

Are you starting a LED project? I have some leftover equipment from my foray into the LED lighting world...also looking to build another fixture for my nano reef tank. We could possibly save on shipping on a few things.
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post #6 of 15 (permalink) Old 03-13-2009, 03:16 PM Thread Starter
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Hoppy,

Are you starting a LED project? I have some leftover equipment from my foray into the LED lighting world...also looking to build another fixture for my nano reef tank. We could possibly save on shipping on a few things.
Yes, I am starting a LED project, but at the moment I am still just exploring the options, trying to see how much money I would be spending if I go through with this. Mostly, for now, I am learning about LED systems. The most recent "design" I am looking at is to use only 3 of these, http://www.luxeonstar.com/endor-rebe...aoe1im80dot2b2, spaced across the length of the tank. This should provide the shimmer of a MH light, and still give more than the 50 micromols minimum lighting I want to use. It looks like this is cheaper than using 8 lower power LED's.

At the earliest I would want to spend money in a month or so - I think. What is your schedule?

I think it was you who pointed me to the great surplus metals place here in Sacramento, the name of which I forget, but it is south of Folsom on Florin Perkins Road. Do you know if they have heat sink extrusions?

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post #7 of 15 (permalink) Old 03-13-2009, 05:36 PM
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Originally Posted by Dalban View Post
Something like this would be more appropriate (and a lot cheaper).
Those are a bit of a waste. Too small IMO to run at what I consider a comfortable temperature. Cooler you can keep the LED, the longer it will live.

Hoppy, HeatsinkUSA is a great place for an extreme heatsink, but it's unnecessary. You could run the array completely passive with something that big.

The triple Rebel star is going to be overkill. Thats going to put a lot of PAR in a small area with the LEDs concentrated together like that. A lot more than the target you are shooting for, unless your tank is really deep.
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post #8 of 15 (permalink) Old 03-13-2009, 06:04 PM
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Those are a bit of a waste. Too small IMO to run at what I consider a comfortable temperature. Cooler you can keep the LED, the longer it will live.

Hoppy, HeatsinkUSA is a great place for an extreme heatsink, but it's unnecessary. You could run the array completely passive with something that big.

The triple Rebel star is going to be overkill. Thats going to put a lot of PAR in a small area with the LEDs concentrated together like that. A lot more than the target you are shooting for, unless your tank is really deep.
Any recommendations for a good heatsink with a compromise between size/cost and it's efficiency?
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post #9 of 15 (permalink) Old 03-13-2009, 06:25 PM Thread Starter
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I'm swinging back and forth between individual heat sinks, one per LED and one big heat sink, serving all of the LED's. Ideally, it seems that a big heat sink is the way to go, but they aren't cheap. That is what made me wonder about using small heatsinks, each with its own cooling fan. Economically that looks good, but I have no idea what the power limitations are for them.

Evil, I hope to keep the fixture about 24 inches from the substrate, and use lenses to concentrate the LED output into the appropriate area. Does a LED with a lens produce anything close to equal intensity throughout the area lighted by the beam?

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post #10 of 15 (permalink) Old 03-14-2009, 12:05 AM Thread Starter
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Does anyone have a good method for estimating the PAR intensity that can be obtained by a LED that emits 100 lumen? I have been dividing that by the circular area that a lens will concentrate the light into, giving me lumens per meter squared, or lux. Then I found some data that give a crude equivalence of 70 lux per PAR unit (einsteins per second).

EDIT: I finally found a table that gives conversion factors for PAR to Lux, for various light sources, not including LED's of course.

Hoppy

Last edited by Hoppy; 03-14-2009 at 04:07 AM. Reason: Add more information
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post #11 of 15 (permalink) Old 03-16-2009, 02:57 PM
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A lense will make the light gradient more consistent across the total angle. The dropoff will be fast at the outer edges, but it's only in the last few degrees. You can usually find the irradience plots for the lenses on the manufacturers website.

I have done some experiments with optics at different depths, and may be able to give you a direction to head. With 40 degree optics, I was able to hit 200 PAR at 24" in my freshwater tank. This was on an array running Cree XR-Es at 1000mA. To get to your target level, running at 700mA on the driver you are looking at, and going to a 60 degree optic will make the PAR levels a lot more tollerable for your application. You could also try 80 degree optics. They are usually cheap enough that it won't break the back to experiment a little with them, and they swap out fairly easily.
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post #12 of 15 (permalink) Old 03-16-2009, 04:16 PM Thread Starter
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Evil, do you have data to share about the PAR readings you got, using those Cree LEDs , at various depths in the water? Some data would make deciding how to get to a specific PAR reading a whole lot easier.

Hoppy
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post #13 of 15 (permalink) Old 03-17-2009, 07:16 PM
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Beyond what I have stated in my last post? Not really, but I could take some more readings for you. I have 40, 60, and 80 degree lenses that I can experiment with. Give me a few days to get it all together (I'm trying to get my new reef tank situated).
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post #14 of 15 (permalink) Old 03-17-2009, 07:19 PM Thread Starter
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Originally Posted by evilc66 View Post
Beyond what I have stated in my last post? Not really, but I could take some more readings for you. I have 40, 60, and 80 degree lenses that I can experiment with. Give me a few days to get it all together (I'm trying to get my new reef tank situated).
Thank you very much! That will be extremely helpful. I'm finding the LED world to be about as much more complicated than fluorescent lighting as planted tanks are compared to fish only tanks. Big learning curve!

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post #15 of 15 (permalink) Old 03-18-2009, 06:47 PM
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It's just because it's new. All the kinks and peculiarities haven't been worked out yet. The planted world has been neglected so far, but even with me doing reef setups for a while now, I'm still learning and tweaking things as I go.

At least with planted setups you don't have to worry about high kelvin color temps and color blending
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