What size heat sink for LED

[darkside212]

Hey all,

I'm looking to build a diy led fixture for my 75g (SPS tank). I plan on using the 48 led premium diy kit from rapidled w/40 degree optics. I was looking at heatsinkusa.com I'm wondering what size heat sink I should use, or what size I should make the fixture.

any feedback/help is appreciated!

[kcress]

Have you looked at all the DIY LED fixture threads? There is no official size because every case is different. You should peruse those threads to get a feel for what you'd need.

While you're at it consider using aluminum U channel.

[darkside212]

Yeah I've been, but a lot of them are so long....and cluttered

would U channel just be cheaper?

[mike_cmu04]

I dont know if it will be cheaper but it would probably be smaller than a big heatsink

[surff]

Hey all,

I'm looking to build a diy led fixture for my 75g (SPS tank). I plan on using the 48 led premium diy kit from rapidled w/40 degree optics. I was looking at heatsinkusa.com I'm wondering what size heat sink I should use, or what size I should make the fixture.

any feedback/help is appreciated!

I use 2" center to center spacing, alternating the white and the blue. I run the whites at about 80% and the blues at about 60%. I happen to use BuckPucks and an Ardunino controller that is programmed to dim the LEDs over a 24 hour cycle.

I run 24 Cree XR-Es on a an 8 x 12 x 1.4 inch heat sink from HeatsinkUSA. Add to that a pair of 120mm fans and the junction temperature is 90 F. (4 heat sinks, 96 LEDs) I use a temperature governed speed controller on the fans. (no fan noise) Tank is 60 x 24 x 24. I am not running any optics on a mixed coral tank.

How deep is your tank? You may not need the optics...

One can choose to epoxy the LEDs (Star mounted) to a heat sink or screw them down. Yes, drilling and tapping all those holes is a bit of work. The reason I did it is so I can remove a LED if needed. Removing an epoxied Star is a prime B****! :mad:

FYI, the lower you keep the junction temperature, the longer the LEDs will last and if you run them at 80% of rated power, that will also tend to keep the color temp constant and increase longevity.


Hope this helps

[darkside212]

Definitely helps thanks!

wow no optics? I would have thought you needed them on a 24" tank. I have a standard 75g tank 48x18x20 (SPS dominated)

[jimnrose]

I used 5(1.5" x 1.5" x 60") U channels for my 72" x 24" x 17" tank. I agot them from a window awning manufacturer (very reasonable). I cross strapped them with 1" aluminum from HomeDepot.
The advantages are design flexiblity and lighter weight as well as cost. BTW the heat sinks are near room temp with only a slight aid from muffin fans'.

[cyrusthevirus]

I am using "C" channels on my build. I find that they are much lighter than the heatsinks and easier to work with. I ordered them from the site below and they were reasonably priced even with shipping.

http://www.speedymetals.com/pc-2530-8348-1-x-1-x-18-channel-6063-t52-aluminum-extruded.aspx

[darkside212]

thanks they have decent pricing. I will be checking them out. I guess my main concern was keeping the LEDs in optimum running temperature, but it sounds like it is pretty easy with a fan and really any aluminum.

[zangmann]

I'm currently using 3/4"x 3/4" strips with 12 leds on each and they just get too hot with no fan. Try going larger than what is commonly available at HD. I'm thinking using something wider than 1.5" will allow passive cooling.

[darkside212]

yeah kind of sounds like 1.5" is the minimum size to use