Heatsinks for DIY LED lamps

ttystikk

ttystikk

Well-Known Member
SupraSPL said:
Grabbed a bunch a thermometers and settled on this one

http://www.amazon.com/Digital-Candy-Deep-Fry-Thermometer/dp/B0075M5ESY/ref=sr_1_10?s=kitchen&srs=2530581011&ie=UTF8&qid=1446179683&sr=1-10&keywords=taylor thermometer

It gives readings that agree with the mercury, but much faster and easier (10-20 seconds) so I have a lot more confidence in the measurements/ I have abandoned the IR thermometer which has proven to be precise and repeatable, but very inaccurate for measuring aluminum.

These heatsink temps were taken directly behind the COB which was the hottest place on the heatsink that I could find, including the front next to the COB which was a few degrees cooler. Ambient in the tent was ~75F(24C) and there was decent airflow from the circulation fan hitting all heatsinks with a slight breeze.

Passive cooled in flower tent, all driver turned up to max
====================================
CXA3070 3000K AB bin @ 25.5W ea:
8.46"X12", 96F (35.5C) 188cm²/heat W

CXB3070 3000K AD bin @ 24.5W ea:
8.46"X12", 96F (35.5C) 222cm²/heat W
4.9"X14", 96F (35.5C) 153cm²/ heat W

CXB3590 3500K CD bin @ 24W ea:
8.46"X12", 93F (34C) 277cm²/heat W (good demonstration of the law of diminishing returns)
4.9"X14", 93F (34C) 190cm²/heat W (this heatsink was tilted unfavorably for cooling, did not matter)
4.9"X14", 93F (34C) 190cm²/heat W
10.08"X6" 90F (32C) 318cm²/heat W (overkill surface area, but a good data point)

CXB3590 3000K CB bin @ 26.5W ea
10.08"X6" 84F (29C) 247cm²/heat W (these were on the edges, must be getting the best airflow)
=============================================

Passive cooled in veg tent, driver set at maximum
single CXA3590 5K DB 24.5W:
5.88"X6" with slight airflow hitting heatsink 90F (32C), 179cm²/heat W
5.88"X6" with almost no airflow 108F (42C), 179cm²/heat W

According to the PCT, the difference in output between these 2 temps is about 2%.

=================================================

Active cooled veg fixture:
pair of CXA3590s 5K DB @ 85W ea:
3.5"X36" with 2.5W of 80mm fan, 108F (42C), 52.6 cm²/ heat W (measured 4% temp droop)
===================================================

Still digesting this data
Click to expand...
Much appreciated, thank you!
 
L

lednewbie123

Member
Copy and pasting my previous question to move it to the new page hoping someone can reply soon so I can get the order done ^^

I would like to have someone who knows the math verify before I end up wasting $500. Im horrible at math and my numbers dont match whats showed here. Tried figuring out the math that made 10284cm² -> 5.88" X 38" but I ended up with a very diff number and another heatsink profile I did the same math on came out better. Long story short am I correct that the heatsinkusa 7.28inx7in is more surface area than the 5.866inx9.5in
 
bggrass

bggrass

Well-Known Member
lednewbie123 said:
Copy and pasting my previous question to move it to the new page hoping someone can reply soon so I can get the order done ^^

I would like to have someone who knows the math verify before I end up wasting $500. Im horrible at math and my numbers dont match whats showed here. Tried figuring out the math that made 10284cm² -> 5.88" X 38" but I ended up with a very diff number and another heatsink profile I did the same math on came out better. Long story short am I correct that the heatsinkusa 7.28inx7in is more surface area than the 5.866inx9.5in
Click to expand...
Per the sheets,

7 x 342.88 = 2400.16 cm^2 area of the 7.28" profile

9.5 x 260.01 = 2470.095 cm^2 area of the 5.88" profile
 
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L

lednewbie123

Member
So the surface area sqcm is just multiplied by the length you you plan to use? I made that way more difficult than it shoulda been lol. I thought you had to find the sqcm of 5.88x9.5 then multiply or something by the surface area lol
 
Shredderthirty

Shredderthirty

Well-Known Member
ttystikk said:
I'm pretty sure that two of those big fans would be plenty, as long as they're getting reasonably cool air to work with. If they're stuck up in the top of a tent without ventilation for example, they'll get hot just because there's nowhere for the heat to go.
Click to expand...
okay, yeah. really i guess my main question out of all of that is if 10" is wide enough to have three CXB3590 in a row
 
K

kliend

Active Member
joseph1026 said:
After, I removed the LED from the heatsink and figured maybe it is because I did not sand down the heatsink?? Or because there was a thin layer of factory-applied thermal paste plus some of the "Arctic silver 5 high density polysynthetic silver thermal compound" that I purchased and applied myself.

Any advice!
Click to expand...
Don't mix thermal pastes. If the heat sink already has paste, then use it. Or clean it off and apply your own. But once it's down, you can't lift that COB off. If you do, clean off all the thermal paste and re apply.

Sry for grammar on an iPad.
 
nug jug

nug jug

New Member
SupraSPL said:
Finally got around to organizing this and I figured it might come in handy for those who are designing DIY lamps. These charts show the surface area and surface area/cost for each of the Heatsink USA profiles.
View attachment 3300177

So in summary, the cheapest surface area is the 2.08" profile. It gives a lot of spread, maybe too much spread for our purposes. The 4.85" is also cheap and might be good for a vegging heatsink. Thin base plate though, not ideal for COBs.

The 4.6" serrated is a good value and it has a .23" baseplate thickness/riser height so it might be good for COB and gives a good spread between COBs. It has decent height to the fins, so uses active cooling efficiently (120mm fan should cover all fins). The 4.9" has a thick.3" base plate and still gives a good spread, should be very good for high powered COBs. Same with the 5.88" and it fits 140mm fans.
Click to expand...
Can I put 3 cxa3590 77V (run at 1A?) on your 4.9", 3" baseplate heatsink?

How many fans that you mentioned do you recommend for such a setup?

I can't find your spreadsheet on cob vs driver with respect to varying currents and their resultant efficiency.

I just need 3 cobs, a heatsink, the proper driver from that spreadsheet, and the related tools and accessories. Thanks brothers

Edit: would this heatsink be good for using cob holders? Without a drill press, am I reduced to only soldering the cobs to the heatsink ?
 
littlejacob

littlejacob

Well-Known Member
nug jug said:
Can I put 3 cxa3590 77V (run at 1A?) on your 4.9", 3" baseplate heatsink?

How many fans that you mentioned do you recommend for such a setup?

I can't find your spreadsheet on cob vs driver with respect to varying currents and their resultant efficiency.

I just need 3 cobs, a heatsink, the proper driver from that spreadsheet, and the related tools and accessories. Thanks brothers

Edit: would this heatsink be good for using cob holders? Without a drill press, am I reduced to only soldering the cobs to the heatsink ?
Click to expand...
Bonjour
No...I believe you need a special device to solder aluminum...!
Do you have an electric screwdriver (don't know the name...!)
Or self tapping screw!
Or kapton tape!
Even a dremmel should work!
And for 3x cxb 3590 3500ºk 36V cd you need an hlg-120-1400b... (150w)!
What is the size of your box? (2x2?)
Is it for bloom only?
You're going to be happy with those cob!
Have a great day ★
 
SupraSPL

SupraSPL

Well-Known Member
@nug jug

CXA3590 5K DB 2.png

CXB3590 5K CD Verical.png

3 of them at 1A = ~240W @ 51% efficiency so that is 118 Watts of heat. For active cooling you want a minimum of 40cm²/heat W = 4704cm². A 4.9"X20" fits the bill, with a single 120mm fan in the center blowing onto the heatsink. If you want to spread them out further you could use 3.5"X37" with a 80mm fan

All that said, that setup would require something like an HLG-240H-C1050 which is not readily available as far as I know.
 
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qwerkus

qwerkus

Well-Known Member
nug jug said:
Can I put 3 cxa3590 77V (run at 1A?) on your 4.9", 3" baseplate heatsink?

How many fans that you mentioned do you recommend for such a setup?

I can't find your spreadsheet on cob vs driver with respect to varying currents and their resultant efficiency.

I just need 3 cobs, a heatsink, the proper driver from that spreadsheet, and the related tools and accessories. Thanks brothers

Edit: would this heatsink be good for using cob holders? Without a drill press, am I reduced to only soldering the cobs to the heatsink ?
Click to expand...
Aluminium soldering is not very complicated, but I wouldn't advise it, as most aluminium items are coated, which results in an incredible mess during soldering. For the rest, you can easily drill without a press. Doesn't matter if the screws are slightly skewed - it will hold. As others suggested: use m3 stainless steel screws of good quality - no need for tapping with aluminium. You can even recycle 6-32 computer screws, though since most of them are bad quality, you'll need 2 per hole - one will die in tapping, the next one will hold!
 
nug jug

nug jug

New Member
@SupraSPL i originally wanted 4x cxb 3590 36V run at 1.4A (iirc that's most efficient)? However, this single light will be used for all stage of plant life. The lack of color temp. availables steered me to cxa.

How important is color temp? Now I see to run cxa at .2 amp would cost a lot up front because I'd need a lot. I would still love to throw 4 cxb 3590 at 1.4A and active cooling - what's the deal with color temp?

Others - thanks for help. I have drill, no drill press. Supra - what's the title of your thread that matches drivers to cobs? Is it deeper in your stickier, aptly-named thread?

2x2 looking for 200 usable watts total. Active cooling PC fan and overkill inline fan with controller
 
ttystikk

ttystikk

Well-Known Member
nug jug said:
@SupraSPL i originally wanted 4x cxb 3590 36V run at 1.4A (iirc that's most efficient)? However, this single light will be used for all stage of plant life. The lack of color temp. availables steered me to cxa.

How important is color temp? Now I see to run cxa at .2 amp would cost a lot up front because I'd need a lot. I would still love to throw 4 cxb 3590 at 1.4A and active cooling - what's the deal with color temp?

Others - thanks for help. I have drill, no drill press. Supra - what's the title of your thread that matches drivers to cobs? Is it deeper in your stickier, aptly-named thread?

2x2 looking for 200 usable watts total. Active cooling PC fan and overkill inline fan with controller
Click to expand...
I'm running multiple modules, each of which will be 4 x CXB3590 @50W for the 56% efficiency. I chose 3500k color temp after seeing people use them successfully in both veg and bloom.
 
nug jug

nug jug

New Member
ttystikk said:
I'm running multiple modules, each of which will be 4 x CXB3590 @50W for the 56% efficiency. I chose 3500k color temp after seeing people use them successfully in both veg and bloom.
Click to expand...
Thank you!! And sorry to supra - i found the chart as the second attachment to you post.

Where did you source cobs? Digikey?
 
Waiks

Waiks

Well-Known Member
I want to run 6 vero 10's @350ma on a 32"L x 2.079"W H.USA.
I plan on placing two 50mm fans on top, one @ 8" the other at 24"
Would this keep the cobs cool? I want to lean on the overkill side of cooling.
Thanks!
 
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