Heatsinks for DIY LED lamps

doz said:
Well just as reference, I tested my 2 lights. I typically run them with a 240mm fan http://www.amazon.com/Cooler-Master-MegaFlow-200-Computer/dp/B008G3OLRQ/ref=sr_1_1?ie=UTF8&qid=1447008745&sr=8-1&keywords=240mm fan and they stay cool to the touch. They are 18x10 (10" profile) from HeatsinkUSA with 4x CXB3070 cob pushed @ 50w each (200w total). While I understand the requirements for passive, I wanted to see how hot it would really get.

After leaving them on for about 30 minutes (no more rise), the light with the fan off got quite hot. The heatsink in the center (furthest point but equal from all 4 COBS) was getting up to 43c while the one with the fan running was sitting at 29c.
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as a passive fail safe condition 43c is pretty good.
 
Well, it was a good bit hotter near the cobs. That 43c was towards the center and while fail safe it would be fine still I fully believe, I would not want to run it daily like that. With the infrared sensor I have, its a pain in the ass on the lights. It does not pick up the aluminum temperature very well. I sometimes have to put tape (the kapton is what I usually aim for) to pick up the real temp depending. Kinda weird.

But yes, I agree that I would be comfortable if a fan failed. I have no way to measure the output other than my kilawatt. I did not notice a drop in power draw, stayed consistent so it didnt seem to hit a temp wall (although I am sure the efficiency was down).
 
From searching on this site I've learned: Passive cooled designs with a heat sink area of 110 CM2/W(thermal) will run at about a 10 degree C rise above ambient. The Vero 18 at test current dissipates about 60% of the energy supplied, stated another way is 40% efficient. A 29" length (chosen based on my planned spacing of 9.5") of the heat sink USA 4.9" profile ($51.62) will cool 3 Vero 18's (54 thermal watts) using the Supra recommendation. Good golly miss Molly that's a thermal resistance of 0.185 degree C/W! The commercial heat sinks are WAY WORSE at any price! 2 heat sinks and 1 driver makes a 180W lamp. 4 lamps to cover a 4 foot square (the center has no COB over it), about 45W/sq ft.
 
I found Supra's posts on actual testing and at 115CM2/W he had a 9C rise above ambient while at 90CM2/W he had 11C rise. I can switch to the 4.85 profile ($28.42) which would be 106CM2/W rather than the 124.8CM2/W that the 4.9 ($51.62) gives and still be under 10 degree C rise. But I'll stick with the 4.9 even though it's ultra conservative mainly because of the thicker base plate (0.3" vs 0.14"). I could even go to 1.4amps with the unavailable HLG-240H-C1400B.
 
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Well I'm glad I haven't ordered any parts yet because I'm not pleased with the efficiency and PAR output, mainly because of the Vero 18s. I'm now thinking of 16 Vero 29's instead of 24 Vero 18s to cover a 4 foot square. I'll still build 4 " fixtures" but each will cover a 2' x 2' square. Spacing the COBs 1' each way, 2 per 23" heat sink. The Vero 29 is 44.5%+ efficient at 1.4 amps so each heat sink deals with 56W. 23" of the 5.88 profile comes out 107cm2/w, a bargain at $40.02. Unfortunately the driver match is not as pretty with the Vero 29, until the HGL-240H-C1400B is available I'll use the HGL-120-C1400B to drive 2 cobs. Roughly $300 in material yields a 200W fixture that'll deliver 22.25 par watts /sq ft. Now I'm thinking of adding some red "stars" to shift the spectrum for flowering and use up some of the excess driver capacity. The drivers will allow addition of 20 red stars, maybe more, to each heat sink (2 parallel strings of 10, about 29.4W) but that's probably pushing the heat sink. What efficiency are red stars?
 
Jerry Liebler said:
Well I'm glad I haven't ordered any parts yet because I'm not pleased with the efficiency and PAR output, mainly because of the Vero 18s. I'm now thinking of 16 Vero 29's instead of 24 Vero 18s to cover a 4 foot square. I'll still build 4 " fixtures" but each will cover a 2' x 2' square. Spacing the COBs 1' each way, 2 per 23" heat sink. The Vero 29 is 44.5%+ efficient at 1.4 amps so each heat sink deals with 56W. 23" of the 5.88 profile comes out 107cm2/w, a bargain at $40.02. Unfortunately the driver match is not as pretty with the Vero 29, until the HGL-240H-C1400B is available I'll use the HGL-120-C1400B to drive 2 cobs. Roughly $300 in material yields a 200W fixture that'll deliver 22.25 par watts /sq ft. Now I'm thinking of adding some red "stars" to shift the spectrum for flowering and use up some of the excess driver capacity. The drivers will allow addition of 20 red stars, maybe more, to each heat sink (2 parallel strings of 10, about 29.4W) but that's probably pushing the heat sink. What efficiency are red stars?
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If efficiency is what you want, buy CXB3590 chips. The up front cost is only once and they'll save you power for as long as you use them.

Four of them driven at 50W and the 200W driver to power them will cost you less than $250. If you choose the 3500k CD bin chips, efficiency with this combination is 56%, for comparison purposes.

This combo is nearly twice as efficient as any HID lamps currently on the market, and this is certainly true after the second month of operation; lumen depreciation doesn't affect COB LED.
 
Bonjour
@ttystikk where do you found this at that price?? 250$!!
Cxb 3590 are 42.50 $ each...170 $ +70 $ for the driver...hs 60 $...fans...12v psu...TIM...wire...holders...wago...pots...resistor...fuse...!!!
About 350$! For small order!
Have a great day ★
 
littlejacob said:
Bonjour
Are you talking about the 1000X165X35mm aluminum radiator from tme? (36.50 €...43 € vat included!)
If it is this one I split this one in 4 part with cxb 3590@1400mA on each...it gets hot so if you let it like it is and don't split it you will need a 140mm fan or 4 x80mm! Plus a 50mm for the driver!
Have a great day ★
Click to expand...

but reference to estimates Supra

(4) CXB3590 3500K CD 36V @ 1.4A (49W ea)
(1) HLG-185H-C1400
196 dissipation W -> 85.7W heat ->
passive cooled heatsink 10284cm² -> 5.88" X 38" heatsink (could split in 2 to improve uniformity/spread)

It should not be worth?

Perimeter = 84cm (3cm 14fins 2 sides) + 34 (x2 base) = 118cm x 100cm perimeter length = 11800cm2 !!!! also it is larger than the recommended 5.88 Supra

thanks for answering,
 
littlejacob said:
Bonjour
@ttystikk where do you found this at that price?? 250$!!
Cxb 3590 are 42.50 $ each...170 $ +70 $ for the driver...hs 60 $...fans...12v psu...TIM...wire...holders...wago...pots...resistor...fuse...!!!
About 350$! For small order!
Have a great day ★
Click to expand...

I said only for COBs and driver! Thank you for completing the list of necessary components!
 
ttystikk said:
Quantity discount?
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it could be a cultural difference. Perhaps Jerry is used to being negotiated with a little bit. he quoted me $46.50 each for what I considered a bulk order of 32 units. Maybe If I would have tried a bit harder, I could have saved $160....
 
Hello all. Can you help me with calculation for CXA 3070/0.7A passive build heatsink dimension?
I plan to use black anodized heatsink like this:
18.jpg msg-12416-0-69605200-1446889133.jpg
I think 1 ft of it might restrain my cxa temps. What do you think?
 
If I'm going to "abandon" the Veros for CRE due to efficiency, the CXB3590 CD bin isn't the only choice, though it appears to be the most efficient. Perhaps The CXB 3070 BD bin is more price friendly & still offers great efficiency ( 54+%).
 
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