Heatsinks for DIY LED lamps

Dawamesk

Dawamesk

Active Member
Hi guys !

Very interesting stuff in this thread ...again ;)

I'm about to build my own pannel and I'm a bit worried about the heatsinks I've just received ... I plan on using them for passively cooling CXA3070AB from 700ma to 1050ma and I'm concerned about them efficiently doing so.

Although they're said to be able to passively handle 70w of dissipation (see here: http://www.ebay.de/itm/Alu-Kuehlkoerper-fuer-10-120-W-Watt-LED-Chip-Heat-Sink-DIY-Fluter-SMD-Flutlicht-/111362015923?ssPageName=ADME:L:OC:NL:3160) the current discussion of this thread and some warnings that have been sent at me already might push me to reconsider ...

Of course, I could just mount a cob on it and give it a try but I will use a single driver to power 4 cobs (HLG-120H-C1050B 155.4W 1050mA 74-148V) so it means I would have to mount all 4 cobs on their respective H/S and wire up the whole thing before I can perform some tests ... when the H/S fails to handle the temperature dissipated by the cobs I'll have to dismentle the whole setup and start over.

That's why I'd like to know what you think of those heatsinks before I proceed ... If you guys think they'll not make it I'd rather get some Alpine 11 plus CPU cooler than build everything using those ones and notice they are too weak ...

Once again your advices might spare me a lot of hassle !
 

Attachments

SupraSPL

SupraSPL

Well-Known Member
Hey bud, I think you are right to be concerned on those, glad you discovered that beforehand. Those drill holes behind the COB might be a problem as well. @stardustsailor ran into a problem with an air bubble behind one of his CXAs, although I think he was running at 2.1A rather than 700mA. The driver would be able to power a single COB so you could test it on just one if you wanted to. Although the drivers states a minimum Vf range, it can go way below it. The upper Vf range is a hard cap though.

The Alpine 11s would work great and would be very overkill, which is fine you can run the fans at 4.2V and they would be silent. If you want to stay with passive you could use 5.88"X6" chunks from heatsinkUSA, ~$13 ea cut and shipped.
 
Dawamesk

Dawamesk

Active Member
SupraSPL said:
Hey bud, I think you are right to be concerned on those, glad you discovered that beforehand. Those drill holes behind the COB might be a problem as well. @stardustsailor ran into a problem with an air bubble behind one of his CXAs, although I think he was running at 2.1A rather than 700mA. The driver would be able to power a single COB so you could test it on just one if you wanted to. Although the drivers states a minimum Vf range, it can go way below it. The upper Vf range is a hard cap though.

The Alpine 11s would work great and would be very overkill, which is fine you can run the fans at 4.2V and they would be silent. If you want to stay with passive you could use 5.88"X6" chunks from heatsinkUSA, ~$13 ea cut and shipped.
Click to expand...
Supra ... first nuff respect for all the work you've done so far and thanks for the quick reply !

OK I'll give it a try with a single cob then and see how it goes ... maybe they'll be ok in which case It would be a good catch since they're not so expensive ... who knows ?!

You said ''The upper Vf range is a hard cap though'' does it mean I should also worry about my driver not being able to handle 4 cobs at 700ma or 1050ma ?

Thanks again ! I will definitely come back here to give you guys some some feedback when the test will be done !!
 
SupraSPL

SupraSPL

Well-Known Member
That is correct. I just ordered some 5.88"X6" chunks to passive cool CXA3590s (@350mA 25W) so if you were to wait a bit I can report back on how well they perform. My vegging room has very little air movement unlike the flowering rooms AND I dump the heat from the flowering rooms into the vegging room, so it will be a good test to see if they can keep temp droop to a minimum without a fan.
 
T

Tazbud

Well-Known Member
Dawamesk, sounds like your getting it worked out, how thick is the top plate on those sinks? maybe you could flip those things and use the other end to mount your cob? They may only need a breeze from the side to tame the low power?
 
Dawamesk

Dawamesk

Active Member
SupraSPL said:
That is correct. I just ordered some 5.88"X6" chunks to passive cool CXA3590s (@350mA 25W) so if you were to wait a bit I can report back on how well they perform. My vegging room has very little air movement unlike the flowering rooms AND I dump the heat from the flowering rooms into the vegging room, so it will be a good test to see if they can keep temp droop to a minimum without a fan.
Click to expand...
Supra I really don't know how to thank you for all this :clap:... of course I can wait till you provide us with feedback on those 5.88 heatsinks and in the meantime I'll give my H/S a try and see how they behave !

Tazbud, yes I'm close to the end of my pre-build research now and it was only possible thanks to this unbelievable RIU community :) I will first try those H/S out the normal way but If I encounter any air bubble problem I'll then follow your advice and use them upside down and see how it goes !

Will report back the outcome by the end of next week !
 
B

bondoman

Well-Known Member
AquariusPanta said:
This seems like the suitable thread to ask this question: When mounting a COB to a CPU h.s., such as the Arctic Alpine 11 Plus, would one need to simply drill a hole for a slightly thicker self-tapping screw in order for a secure mount?

I've read a bunch of people go about tapping by hand after drilling; I don't know if their talking about with screws or with bolts/with tool tap.
Click to expand...
sears has a 4-40 tap/ drill bit combo for around $4. I've used it for around 20 taps and it's still like new. I think more important is the hole you first drill, use a drill press if you can, and make sure to back it out 1/4 for every revolution. No reason to use anything else but a hand tap for soft aluminum with small screws. I also use clipper oil to lubricate it.
 
bicit

bicit

Well-Known Member
I can't comment on copper just yet. It's a bit trickier than aluminum. So far as I can tell, slow speeds, bright finished drill/tap, and copious amounts of lube. I'd still recommend a thread forming tap.
 
Dawamesk

Dawamesk

Active Member
Following this thread and Supra's advices I just end up thinking a 12'' H/S model with a 16'' length from HeatSinkUSA (C/W/3": approximately .85) might be perfect for my setup: 4x3070AB @ 1050ma max

- First, because of thermal efficiency, If I understand this threads correctly it should give something like this:

4x3070AB @1050ma is about to be 150w total.

With a 40% efficiency they will dissipate 90w of heat (should be even less than that since efficiency will normally be above 40% ...)

90w x 0.85 c/w/3" = 76,5 degrees per 3"

Considering the H/S length will be 16'' I should see a temp droop of +- 14degrees celcius above ambient temp (76,5/[16/3]=14)

This sounds super good does it ? Even better when we take into account a higher than 40% effciency @1050ma and the needed air circulation of a grow space ...

- Then, because the size of the heatsink would nicely fit my 2x2 tent and it will also prevent me from building a pannel since I should be able to just hang this chunk of alluminum to the tent hanging tubes.

Only cons I can think of are the price (but it remains doable), the weight of such a large H/S (about to be 9.6lbs or 4.4kg) and the space between the 4 cobs. Would this size of H/S be suitable for a good light distribution in a 2x2ft. tent ? If so, what would be the spacing you guys recommended?

It's amazing how this forum has improved my overall knowledge of thermoelectronics, I would not have been able to understand a quarter of what I've typed in this post just a month ago :mrgreen:
 
C

churchhaze

Well-Known Member
You should probably be fine.

If you're good at geometry and trig, take an isosceles triangle with a top angle of 120 degrees. Given a 2 foot base, you should be able to calculate the height that would give you that base.

If you slice the triangle down the middle, you can just use law of sines on one of the right triangles and use radius instead of diameter. (twisting the triangles around the Y axis gives you a cone, and chopping the cone at 'canopy' gives you a circle.)

Of course that's just a rough calculation based on the output pattern being 50% intensity at 60 degrees in either direction.

Dawamesk said:
12'' H/S model with a 16'' length
...
Would this size of H/S be suitable for a good light distribution in a 2x2ft. tent ? If so, what would be the spacing you guys recommended?
Click to expand...
 
Last edited:
UKpeanuts

UKpeanuts

Well-Known Member
Hello, Just connected a alpine 11 up to a plug in 12v dc supply, first the fan was sucking so I swapped the black and red wire positions from the fan thinking this would change the direction of the fan, but know it wont run at all!
 
bicit

bicit

Well-Known Member
The alpine 11 gt fan has little vent holes at each corner of the plastic housing. Air will vent out of these and could possibly give the perception of them 'sucking' air out. Hold a small strip(narrow and long) of paper over the fan itself. It should get sucked into the fan.
 
Dawamesk

Dawamesk

Active Member
churchhaze said:
You should probably be fine.

If you're good at geometry and trig, take an isosceles triangle with a top angle of 120 degrees. Given a 2 foot base, you should be able to calculate the height that would give you that base.

If you slice the triangle down the middle, you can just use law of sines on one of the right triangles and use radius instead of diameter. (twisting the triangles around the Y axis gives you a cone, and chopping the cone at 'canopy' gives you a circle.)

Of course that's just a rough calculation based on the output pattern being 50% intensity at 60 degrees in either direction.
Click to expand...
That's a good and useful explanation thank you buddy !

I'll probably go that way then ... Supra what would you think of this kind of setup ? 12"x16" H\S sounds good enough to you Boss ? I think I can't really go wrong with it (should normally be enough room for error in my calculation) but your expert eyes for sure will see clearer than my rookie sight :hump:
 
Last edited:
You must log in or register to reply here.
Top