Heatsinks for DIY LED lamps

bicit

Well-Known Member
I get the simplicity!

btw with the right setup, a larger fan (120 mm, 140 mm, 200mm ) can move more air more efficiently than a bunch of wee little buzzers. They are also a lot quieter.
A 30w 52" ceiling fan moving 6200cfm is even more effective if were talking about the ' right setup :P

They may move more air, but they also draw more power. Sometimes more airflow isnt needed. The only case for 120mm fans imo is that theyre cheaper usually.

Otherwise a 5v 80mm fan over the channels of the heatsink is more than sufficient.
 

HydroDC

Well-Known Member
My heat sinks will be mounted to a 24x24 piece of aluminum. Was just wondering if it will help further dissipate some heat.
So, COB mounted on bottom aluminum plate and heatsinks mounted on top of plate above where COB is? Others will know more about this than I, but I think this will adversely affect the cooling. Heatsink surface will probably not be perfectly flat with reluctant air gap(s) when mounted to plate. Most people using heatsinks just mount COB to heatsink. You could be the one who experiments with this.
 

PurpleBuz

Well-Known Member
So, COB mounted on bottom aluminum plate and heatsinks mounted on top of plate above where COB is? Others will know more about this than I, but I think this will adversely affect the cooling. Heatsink surface will probably not be perfectly flat with reluctant air gap(s) when mounted to plate. Most people using heatsinks just mount COB to heatsink. You could be the one who experiments with this.
I think he meant cob -> heatsink -> aluminum plate. Depending on how its mounted it could block airflow ?
 

Stephenj37826

Well-Known Member
What I'm going to do is mount cob to heat sink. Mount heat sink to plate cutting holes in plate big enough for cob and holder. Then mount lense to choice over the holes. The plate will be thin haven't sourced it yet. Possibly steel even. It will be in a case with 2 6" inlets. Air cooled led.
 

bicit

Well-Known Member
What I'm going to do is mount cob to heat sink. Mount heat sink to plate cutting holes in plate big enough for cob and holder. Then mount lense to choice over the holes. The plate will be thin haven't sourced it yet. Possibly steel even. It will be in a case with 2 6" inlets. Air cooled led.
Might be easier to mount the lens to the heatsink as well and cut the hole large enough for the lens to poke through as well.

Otherwise sounds like a great idea.
 

PurpleBuz

Well-Known Member
What I'm going to do is mount cob to heat sink. Mount heat sink to plate cutting holes in plate big enough for cob and holder. Then mount lense to choice over the holes. The plate will be thin haven't sourced it yet. Possibly steel even. It will be in a case with 2 6" inlets. Air cooled led.
the metal plate could increase the cooling if there is enough contact between the heat sink and the plate, if that's your objective using aluminum would be better than steel.
 

Stephenj37826

Well-Known Member
the metal plate could increase the cooling if there is enough contact between the heat sink and the plate, if that's your objective using aluminum would be better than steel.
Yeah just thought why not use aluminum. Also would you put any thermal grease/adhesive between them maybe around each cob
 

PurpleBuz

Well-Known Member
Yeah just thought why not use aluminum. Also would you put any thermal grease/adhesive between them maybe around each cob
I would choose my heatsink so that its wide enough to make lots of contact to the aluminum plate, and apply a silicone base thermal grease between the heatsink and the aluminum plate and using nuts+bolts to secure the heatsink to the plate. so that you can apply some pressure.

I'm designing something similar hoping to use an aluminum channel as the base of the unit, and drilling some large circles into the channel for the cob+heatsink. I got a set of hole saws for steel and can't wait to try them out. The aluminum channel should cut out like butter!
 

PurpleBuz

Well-Known Member
A 30w 52" ceiling fan moving 6200cfm is even more effective if were talking about the ' right setup :P

They may move more air, but they also draw more power. Sometimes more airflow isnt needed. The only case for 120mm fans imo is that theyre cheaper usually.
a 120 mm fan on a 5" wide heatsink will use less power to get the same airflow from 80 mm fans. especially considering that it will take at least two 80 mm fans to cover the heatsink.
 

Organja

Well-Known Member
I saw a thread on here somewhere with w covered situation going on... It looks legit, also I've also been thinking a lot about air cooled hood situations for the LED's. Big fans on high, more control, better cooling, maybe direct fins to run along same direction as air flow, constantly drawing air through thr whole sink, and beyond!

--------- Heat sink
||||||||||||
Airflow
^
|
 

bicit

Well-Known Member
a 120 mm fan on a 5" wide heatsink will use less power to get the same airflow from 80 mm fans. especially considering that it will take at least two 80 mm fans to cover the heatsink.
Depends on the length of the heatsink. 20 inches or less and a single 80mm fan is sufficient. As long as the fan is blowing into the channels above the cobs.

80mm fan draws .16 ma, 120mm draws .22 ma @ 12v. More power is more power which means less photons per joule
 

PurpleBuz

Well-Known Member
Depends on the length of the heatsink. 20 inches or less and a single 80mm fan is sufficient. As long as the fan is blowing into the channels above the cobs.

80mm fan draws .16 ma, 120mm draws .22 ma @ 12v. More power is more power which means less photons per joule

how the f do you get an 80 mm fan to span a 5 or 6 " wide heat sink ?
 

bicit

Well-Known Member
a 120 mm fan on a 5" wide heatsink will use less power to get the same airflow from 80 mm fans. especially considering that it will take at least two 80 mm fans to cover the heatsink.
I'm sorry, just realized I'm not being very clear. I'm not disputing the fact that a 120mm fan will move more CFM/W. (assuming similar models). I'm trying to say that an 80mm fan is 'good enough' in most cases and that further increases in CFM is going to provide diminishing returns.
 
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