DIY 24 royal blues, What kind of heatsink?

[gorey]

Hey guys im doing a 4 foot long with 24 3 watt leds. Its going to be a atinic supplemnt bar. What would be best for a heat sink/ Im trying to go low budget on the build. Can i just use angle iron?

Jeff

[Dave Thebrewguy]

Home Depot or Lowes should have 3/4" aluminum U-channel, 10' is about $10. I'd avoid angle iron, maybe angle aluminum but certainly no steel/iron.

[gorey]

Cool thanks for the info, Will that stay cool enough with 24 3 watters over a 4 foot span?

[Dave Thebrewguy]

24 LEDs in 4' will be pushing it a bit, then again, so is running your LEDs at 3 watts. If you will be running at full power it would be wise to use 2 pieces with 12 emitters on each of them. At 3 watts, I'd want to keep them at least 3-4" apart, you could move them closer together if your current is set a little lower.
What LEDs are you using and how much current will you be running? I'm testing out a couple strings right now on a larger, heavier extrusion with both Philips Luxeon RBs and Cree XT-E RBs. All of the LEDs are running at 960mA and while the Crees put out more heat than the Philips, the 4" spacing is more than enough for either of them. The U-channel has less mass and less surface area but 4" should still be OK at this current level

[gorey]

Cool thanks for the help!!

[widmer]

Greetings from Ann Arbor.

Pro tip 1: If you get 1" U-channel, you should be able to fit the emitters on the inside of the u rather than the outside (assuming they are mounted on the standard 22 mm stars, just take one with you to the store to feel). Looks much cleaner.

Pro tip 2: If you are spreading the LEDs among 2 bars rather than one (which you should do), if you plan to attach the parallel bars to each other, be sure to place a nut or two between them in order to create a gap for air flow.

Pro tip 3: the Cree royal blue XT-Es are the most efficient LED you can get; = least amount of heat per amount of light created.