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Abe
10-09-2011, 03:33 PM
I know that this has been discussed few times already, but can't find it anymore. I am planning to build LED lights for my new tank to be used instead of T5 or PC lights. It will be in addition to 3X 250w MH. My question is how to calculate how many LEDs needed to cover a 72" tank. I am thinking to go with 2 (48in.x 1.1ìn) heat sinks with 24 RB Leds on each heat sink, all are dimmable and with 40 or 60 deg reflectors. what do you guys think, is this enough or should I go with 72in heat sinks and 36 LEDs on each. Thanks.

Dez
10-09-2011, 05:07 PM
72" heatsinks and 16 LEDs on each with no optics. I have 60" heatsinks and only 12 LEDs on each with no optics. Works well. Any more LEDs and they will run too hot and you'll need a fan. I'm assuming 3 watt crees.

mseepman
10-09-2011, 05:51 PM
Unfortunately 16 leds is a little hard to do as a single ELN driver won't power that many. I've been researching DIY LED for a bit now and if you look at the long heatsinks at Rapidled....you should be okay for a few more LED's per row.

Dez
10-09-2011, 06:30 PM
I have the heatsinks from rapid led. They did not recommend more than 12 Leds on my 60" heatsink. With 12 it gets quite warm, with more I think you'd need fans as it would become too got to the touch. It also depends on how high you mount them. You could go with 12 LEDs on a 60" heatsink and mount it a bit higher.

martinmcnally
10-09-2011, 08:18 PM
Your better to go with smaller heatsinks and attach them together with some brackets from Canadian Tire or somewhere. Its pretty expensive to ship a 72in or 48in heatsink. Although having said that if you still want one that long drop me a private message or something we have gotten our manufacturer to ship direct for heatsinks that size, or you could come to Red Deer and pick it up :mrgreen:. That way your only paying for shipping once.

Everyone seems to have a different formula for LEDs but my calculator comes out at 160 for a tank that size. That's for SPS. (LxWxH / 324).

With a setup that size its going to be cheaper to go with a larger driver that can drive 60-70 LEDs.

Martin

Dez
10-09-2011, 08:21 PM
It sounds like Abe is using LEDs only to supplement 3 x 250 watt halides so he won't need 160 LEDs. Only blue ones I think on either side of the halides.

martinmcnally
10-09-2011, 08:23 PM
Oh opps haha. Yea you dont need that many then lol.