Maybe we need a sub-forum for LEDs - how's this heat sink look?

HeneryH · 03/19/2010, 07:08 AM

I was originally going to go with a commercial heat sink but wanted to consider this quick and dirty DIY made from 3/4 aluminum channel from HomeDepot or Lowes.

I know not many of us are thermal engineers but does anyone have any practical experience?

Thanks

video animation:

EDIT - wow, I clicked the thumbnail below and got an error. It should have been an embedded video from Picasa. Try this link directly http://picasaweb.google.com/lh/photo...eat=directlink .

evilc66 · 03/19/2010, 09:32 AM

It's really going to depend on your thermal load, but forced air cooling would be recommended with something like that.

Qwiv · 03/19/2010, 10:20 AM

That would depend on what LEDs and how hard you are going to drive them.

If you were going to use 3w and drive them at 700ma, at a spacing around 2" I would think you are safe with a easy fan blowing across the frame. If you were going to go with driving them at 1000ma I would upsize the fan and make sure your enclosure blows the air across the channels in a very linear manner and not just randomly.

HeneryH · 03/19/2010, 12:17 PM

I was going to run at 833 mA and have not yet decided on final spacing.

I was hoping to run without cooling fans and just leave an open top to radiate the heat away. Air would hopefully come up through the rails as well but might be slightly hindered by the glass.

Qwiv · 03/19/2010, 12:26 PM

You will definitely need a fan. LEDs will get hot locally and you don't have enough meat in the aluminum to passively remove it from the LED source without some direct air movement. You fixture design won't even create a convection current because of how open it is.

If you are using a dimming driver, you can build it and put a temp gauge on it to determine how much you can drive it. I used CREE LEDs and made sure my heatsink right at the LED did not get over 140 deg. F. You will need to test in the worse case environment, hot, humid and lowest air movement.

With so many environmental factors, it is impossible for anyone to say your fixture will work (long term) but you can test yourself.

If you determine that your fixture works when driven to some given amount, make sure you install a resistor to match the setting inline wit your pot so you don't accidentally set it higher.

03/19/2010, 07:08 AM	#1
HeneryH Henery Hawk Join Date: Jul 2009 Location: PA Posts: 1,010	Maybe we need a sub-forum for LEDs - how's this heat sink look? I was originally going to go with a commercial heat sink but wanted to consider this quick and dirty DIY made from 3/4 aluminum channel from HomeDepot or Lowes. I know not many of us are thermal engineers but does anyone have any practical experience? Thanks video animation: EDIT - wow, I clicked the thumbnail below and got an error. It should have been an embedded video from Picasa. Try this link directly http://picasaweb.google.com/lh/photo...eat=directlink . Last edited by HeneryH; 03/19/2010 at 07:14 AM.

03/19/2010, 10:20 AM	#3
Qwiv Persistant Perspective Join Date: Nov 2003 Location: Belmont, CA Posts: 2,168	That would depend on what LEDs and how hard you are going to drive them. If you were going to use 3w and drive them at 700ma, at a spacing around 2" I would think you are safe with a easy fan blowing across the frame. If you were going to go with driving them at 1000ma I would upsize the fan and make sure your enclosure blows the air across the channels in a very linear manner and not just randomly. __________________ If I knew keeping fish would be so hard, I would of had kids by now. Current Tank Info: 50Cube + 250DD + Nano

03/19/2010, 12:26 PM	#5
Qwiv Persistant Perspective Join Date: Nov 2003 Location: Belmont, CA Posts: 2,168	You will definitely need a fan. LEDs will get hot locally and you don't have enough meat in the aluminum to passively remove it from the LED source without some direct air movement. You fixture design won't even create a convection current because of how open it is. If you are using a dimming driver, you can build it and put a temp gauge on it to determine how much you can drive it. I used CREE LEDs and made sure my heatsink right at the LED did not get over 140 deg. F. You will need to test in the worse case environment, hot, humid and lowest air movement. With so many environmental factors, it is impossible for anyone to say your fixture will work (long term) but you can test yourself. If you determine that your fixture works when driven to some given amount, make sure you install a resistor to match the setting inline wit your pot so you don't accidentally set it higher. __________________ If I knew keeping fish would be so hard, I would of had kids by now. Current Tank Info: 50Cube + 250DD + Nano

03/19/2010, 09:32 AM	#2
evilc66 Registered Member. Join Date: Oct 2007 Posts: 245	It's really going to depend on your thermal load, but forced air cooling would be recommended with something like that.

03/19/2010, 12:17 PM	#4
HeneryH Henery Hawk Join Date: Jul 2009 Location: PA Posts: 1,010	I was going to run at 833 mA and have not yet decided on final spacing. I was hoping to run without cooling fans and just leave an open top to radiate the heat away. Air would hopefully come up through the rails as well but might be slightly hindered by the glass.