Heatsinks for DIY LED lamps

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churchhaze

Well-Known Member
Imptspd said:
I have (2) 3k ab's (1) 4k and (1) 5k but I can't remember off hand what bin they are. I built this light in attempt to have a multi stage light for flower and veg, but also as an experiment to see how the different spectrum may be of any benefit or not. I plan on buying more ab 3k's later on and will most likely replace the 4k and 5k.
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You could always reuse the 4000k and 5000k for a veg lamp if it turns out to hinder flowering.

SupraSPL said:
Nice work lmpt! Is that a 3000K for flowering?

CH, love the lamp! What kind of heatsink temps are you getting?
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Thanks man! The sinks are cool to the touch.

I just checked the temps using the temp probe that came with my multimeter. Ambient temperature was about 24C. First I pressed it into the notch next to the LES, which got as high as 70C. Then I pressed the probe against the base of the heatsink right next to one of the cobs, and it got to 35C. I'm guessing Tj is around 80 or 90C, or is that notch a good indication of Tj already?
 
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SupraSPL

SupraSPL

Well-Known Member
That is a good question Alesh I have not tried it. I mounted mine onto Rosewill RCX-Z1 (and I can verify that they will fit on Rosewill RCX-Z200, both have 60X60mm copper pads.

The Vero screw holes are spaced 43mm across from each other, so to have all 4 screw holes used we probably need at least 45mm of flat surface. The Alpine 11 flat surface is 42mmX61mm so maybe if you rotate the Vero just right, all four holes would be able to be secured? I will make a mock up and give it a try
 
K

Kryptoscientist

Active Member
I've been lurking for quite a while and have built a few DIY cob lights thanks to the invaluable help provided by Supra, Positivity, StardustSailor, and many others... So many thanks guys!!!

I want to step up a notch and build something a little more finished now. Looking at running a single vero29 3500k @ ~2 amp (maybe MW HLG80H-42A driver). I considered using the Mechatronix Xtra Iceled 550 fan heatsink or their passive Moduled 134100 but shipping from china is prohibitive. So I was thinking about having a similar heat sink reverse engineered and made locally or something similar to the HSUSA profiles.

I will fan cool the sink but would like the passive cooling to be sufficient to prevent cob damage if the fan fails. I don't expect the passive performance to keep temps in an efficient range, merely to prevent cob replacement. What do you think?

Maybe a HSUSA profile optimized for my application, any recommendations?
 
SupraSPL

SupraSPL

Well-Known Member
Welcome KS. Vero29 @ 2.1A = 80W. So for active cooling in terms of Heatsink USA, a piece of 4.9"X8" gives you 1900cm² or 24cm²/W. I believe in the event of a fan failure your COB would not be harmed because of the thick base, wide space between fins and short fin height. As the temp of the heatsink rises it gets more and more efficient at exchanging heat with the ambient air. That would be especially true if there was any air movement from circulation fans or ventilation fans.
 
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churchhaze

Well-Known Member
With my arctic alpine vero 29 lamps, I use all 4 screws and let the corners hang off.

I prefer all my individual 3.95" x 4" custom heat sinks over the arctic 11 alpines for less than 45W. (I run my old 6x vero 29 setup at 1.05mA)


AquariusPanta said:
I've seen someone mount a Vero 29 to an Arctic 11 Plus with screws, so it is possible. The only downside is that some of the plastic overhangs on the sides, which shouldn't be too much of a concern.
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AquariusPanta

AquariusPanta

Well-Known Member
churchhaze said:
With my arctic alpine vero 29 lamps, I use all 4 screws and let the corners hang off.

I prefer all my individual 3.95" x 4" custom heat sinks over the arctic 11 alpines for less than 45W. (I run my old 6x vero 29 setup at 1.05mA)
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I imagine the customs are passively cooled or?

(Sorry Supra, I haven't memorized or had reason to utilize your numbers from the HS thread :eyesmoke:.)

Also, you say custom. Do you mean custom as in ordering a 4" piece of the 3.945" model or requesting a similar model but with different fins counts, etc.?
 
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churchhaze

Well-Known Member
Yeah, custom 3.95" profile at 4". Most of them have 90mm fans stuck on them, but some of them are run passively and are uncomfortably warm. I still do like them better than the arctic apline 11 versions though. I made some vero 29 units with 3.95x4", and some with arctics.

Passive is really better with shorter fins though, unless oriented vertically for side lighting.
 
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churchhaze

Well-Known Member
After looking at the vero 18 datasheet, I realize that notch is the Tc measurement point. With such a high difference between 70C and 35C, I'm now suspect of my TIM and will remount it and check again. On one of the vero 18, the Tj notch measured 65C.

Comparing the Tc measurement notch temperature to the base of the heatsink next to it could be a good way to measure the thermal interface conductivity to see if it's mounted right. A good thermal interface should make that temperature difference smaller.

The estimate of Tj=95C seems most accurate if Tj is 25 degrees higher than Tc.

churchhaze said:
I just checked the temps using the temp probe that came with my multimeter. Ambient temperature was about 24C. First I pressed it into the notch next to the LES, which got as high as 70C. Then I pressed the probe against the base of the heatsink right next to one of the cobs, and it got to 35C. I'm guessing Tj is around 80 or 90C, or is that notch a good indication of Tj already?
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Positivity

Positivity

Well-Known Member
churchhaze said:
After looking at the vero 18 datasheet, I realize that notch is the Tc measurement point. With such a high difference between 70C and 35C, I'm now suspect of my TIM and will remount it and check again. On one of the vero 18, the Tj notch measured 65C.

Comparing the Tc measurement notch temperature to the base of the heatsink next to it could be a good way to measure the thermal interface conductivity to see if it's mounted right. A good thermal interface should make that temperature difference smaller.

The estimate of Tj=95C seems most accurate if Tj is 25 degrees higher than Tc.
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Thats a bit strange of a measurement. Normally my Tc and heatsink under or near the cob read the same.

When I take the Tc measurement i put the probe on the built in spot with a few layers of kapton over it. That helps i think to get an actual Tc measure and not a radiant heat from the LES
measure
 
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churchhaze

Well-Known Member
I was very suspect of radiant heat altering my reading since the Tj notch is so close to the LES! Thank you. I will still check the thermal interface regardless. Maybe I didn't use enough TIM or there is an air bubble or something.

I will also try to insulate the probe so it's not heated from radiation.

Positivity said:
Thats a bit strange of a measurement. Normally my Tc and heatsink under or near the cob read the same.

When I take the Tc measurement i put the probe on the built in spot with a few layers of kapton over it. That helps i think to get an actual Tc measure and not a radiant heat from the LES
measure
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Positivity

Positivity

Well-Known Member
@churchhaze

I've successfully lowered the cob 5 - 8c by redoing them. Checking contact (sometimes cobs pop out of holders), screwing down firmly, thin as possible TIM, etc.

I like to run the fresh cobs hot for a half hour or so. Maybe up to 60c - 80c. The paste gets much runnier at higher temps and must fill in more evenly is my theory. Seems, they always run cooler after a bit of use so i figure it helps speed things up.
 
alesh

alesh

Well-Known Member
churchhaze said:
With my arctic alpine vero 29 lamps, I use all 4 screws and let the corners hang off.

I prefer all my individual 3.95" x 4" custom heat sinks over the arctic 11 alpines for less than 45W. (I run my old 6x vero 29 setup at 1.05mA)
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Thanks for the answer! Could you please post a photo?
 
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