Heatsinks for DIY LED lamps

robincnn

robincnn

Well-Known Member
SupraSPL

SupraSPL

Well-Known Member
I agree, not the optimal shape for passive but might be OK for semi-passive. They probably shaped it to fit a CPU case. For the price, we could get heatsinkusa 10"X3" which is good for ~20W passive cooled, the downside being $5 cut fee + shipping costs.
 
SupraSPL

SupraSPL

Well-Known Member
@alesh, I did some testing with the CXB3590 4000K CD 36V class. It was mounted onto Rosewill RCX-Z1 with Prolimatech PK3, no COB holder, taped. Beefy COU cooler with large copper pad. COB was tested bare, no lens. At 5V the Rosewill fan was dissipating only .45W.

5V fan, COB @.5A (16.4W) temp droop = .1%
5V fan, COB @.7A (23.5W) temp droop = .4%
5V fan, COB @1.4A (50W) temp droop = .7%
5V fan, COB @2.57A (99W) temp droop = 2.53%

Results were better than expected so I repeated the test and got:
5V fan, COB @2.57A (99W) temp droop = 2.76%

I used every trick I could to get instantaneous readings, used the fastest voltmeter I have (Fluke 115) to measure Vf and "primed" the meter by pulsing it to get the meter in the correct voltage range. Also the lux meter was pre set in the correct range to get a quicker reading. Not sure what to make of the data, based on the datasheet I would have expected something along the lines of 6% temp droop with dissipation at 100W and efficiency ~46%.

As a side note I tested temp droop with the fan running at 6V 9V and 12V. At 12V (2.8W) temp droop was 1.92% in test #1 and 1.94% in test #2. The 5V fan speed gave the best bang for the buck by far in this test.
 
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testiclees

testiclees

Well-Known Member
Blue Raspberry said:
Hi everyone i am looking to get these http://www.ebay.com/itm/Aluminum-Heatsink-20-X-14-X-1-3-8-Milled-/201024776660?pt=LH_DefaultDomain_0&hash=item2ece02a9d4&autorefresh=true to run 3 CXB3590 at 1400ma using passive cooling this should be overkill right? One day i am planning on adding more and not looking to buy more heatsinks down the road. Thanks for the help!
Click to expand...
my math is not so great but i think that heatsink would be good for about 150w passive.

With that size sink and 3590s at 1.4 it seems like just one more cob (&fan) would make sense fo good light spread, you think?
 
B

Blue Raspberry

Member
testiclees said:
my math is not so great but i think that heatsink would be good for about 150w passive.

With that size sink and 3590s at 1.4 it seems like just one more cob (&fan) would make sense fo good light spread, you think?
Click to expand...

I will actually be doing 3 of the in a 2x4 so it will be dam near wall to wall heatsink. 2 on the outside will have 3 cobs on each and the middle will have 2. I will probably have 4 cobs on them in the future. Trying to plan ahead.
 
littlejacob

littlejacob

Well-Known Member
Bonjour
I found 30*30*1mm thermopads with 6W/mk, I am going to try this way.
I know at least one diyer who use some 5W/mk with V29...
Do you think 6W/mk would be enough!? Or really should use Artic silver 5 (supra said it is the easiest to use).
How can I check if my cobs are not damage? Is dimming them the lower I can and check the dies is a good way?
Have a great day ★
 
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