DIY LED Hood: Prebuild Thoughts...

[GMGQ]

Hi All,

I'm just getting back into the hobby, and I know I have to change the bulbs in my setup (it's been over 2yrs!). I have 2x250W MH, and 2xT5 Actinics lighting my 70gal tank (48"L x 20"D x 18"H approx).

Rather than spend $200+ on new bulbs, I'm looking into this whole LED thing. When I first heard of LEDs a couple years ago, they were over $1000 for a setup, and werent that powerful. Now the story has totally changed. Plus with Milad's group buy setup, how can I NOT go this route?? I built my own stand, did all the plumbing, and wired up the power center by myself, so I'm pretty hands on. I'm pretty excited to jump right into this LED thing, it seems easy enough, but I know I better do my research first.

So having said that, I figure I'll ask some questions here and pick the brains of you awesome reefers! I've engrossed myself in researching this stuff for the past week, but I figure I'll ask some questions here, in case anyone else was wondering the same thing (no such thing as a dumb question, right?). Part of this is also me thinking out loud :P

LEDs:
- I want to maintain the 10K colour that I have now with my MH's. Milad told me that this is achieved with 1:1 of Cool Whites and Royal Blues. And with dimming, I can create the whole range of colour temps as well.
- Regarding the number of LEDs, I've been told that 48 is a good number to achieve something equivalent to 250-400W MH. Just looking at my crude piece of excel art, if I had a 36" heatsink, I could evenly fit 9 LEDs per each 6" section, and that would come to 54 LEDs. I like symmetry :P

Optics:
- So I guess these lenses help focus the LED beam down at 40-65 degrees, like a spotlight. Since the LEDs will be at least 10" or higher above the water, it's a no brainer that optics will be needed, yes? OK, then how to decide which angle to choose? I'm thinking either way, the LEDs will be placed only a few inches from each other, so would it really be necessary to get anything wider than 40*? There should be plenty of overlap anyways. If I go wider, I assume the coverage will be a bit wider, but the intensity will be lower? (i.e. not as many PARS reaching the bottom of the tank). But again, there will be lots of overlap. Maybe just have the last row of LEDs on the furthest Left and Right of the heatsink at 60*, and the rest of them at 40*?


(Yes I was bored at work).

Heatsink:
- Speaking of heatsinks, I'm tempted to go with one big 36" long one. They weight is about 18lbs. I'm not too concerned about the weight, I'll rig something to hang it from chains, and I dont intend to mount the drivers in this LED hood. I'm more concerned with even coverage of the 48" tank. I could go with 2-3 smaller heatsink chunks, and I'll probably never notice any gaps of coverage betwene the chunks. But it seems nicer to have one big heatsink...

Driver:
- I see most builds have 4 drivers to power 48 LEDs (12 LEDS per driver). But I saw other builds (i.e. Milad's) that use 2 larger drivers to control them all. Sure, why not? More hardware = more to wire up + more ways to screw up :P I dont intend on running the lights east to west to simulate the sun, so I dont really see a need to get a bunch of smaller drivers... Agreed?
- Regarding dimmability, I guess dimming is a good thing. I do want to be able to have a controller slowly raise the intensity during the day, then slowly reducing it at night, then I want to run the blue LEDs at a lower intensity for moonlights.

Controller:
- I'm a bit stumped here. As per above, I want to slowly raise the daylight intensity, slowly reduce it, then run the blues at a lower intensity in the evening (like actinics), then lower the blues even more at night for moonlight. What kind of controller will do this for me Automatically? I looked up the Neptune AquaController Apex System, but that sucker starts at $500! Is there a cheaper alternative that will automate the lighting intensity for me? I dont really need all the bells and whistles of the Apex system, I just want something to control the lights on a timer for me...


Ok, those are my initial ramblings. Thanks in advance guys, I'm very excited!

Gary