Reef Lighting Challenge

I have a challenge for the LED modders here. I have been researching LED's for over a year and want to start a fairly costly project for a small coral reef tank. If it is successful and cost effective it will be scaled up and picked up by our Reef Tank community. I want to avoid wasting time/money so I am asking for help in advance. Here are my specifications:

mounted in 2.5 gallon aquarium hood
6"x8" circuit board
will use current limitting resistors
capacitors to smooth voltage and for light fading effect (sunrise/sunset)
small PC fan for cooling
runtime 10 hours/day
LED's to be 10,000K temp range
desired spectral peaks at 420nm, 460nm, 550nm

ideas:
125 - 10mm ultraBright 80,000 mcd -- rated at 20mA, 3.3V typical - powered by dual 1A 16 VDC wall transformers
or 8 - 3W luxeons (heat would be a big issue though with these)

Goal:
pack as much focused light in this area as possible
heat to a minimum
cost under $200


Any suggestions/potential issues you see?

I know a little about tanks and the lighting is one of the most important parts of a reef. Before you jump into LED's as your main source of lighting, I would make sure that they not too narrowband in terms of wavelength. Reefs may need a bit more of a full spectrum than LED's can provide.

Also, for fading, you will want to use some sort of PWM for control. Caps wont do it.

the spectrum seems to be fairly close to that of a traditional 10K bulb, but lacking in the 420 nm range which is questionable photosynthesis range for corals anyways.

Pulse width modulation will probably be a bit too costly considering the amount of amps and 125 LED's to be used.

But I'll look into that more. I would like more suggestions concerning Light output though.

if I go with powercompact light, they would offer 1650 lumens across 2 - 13W bulbs. So I want to know if this would be comparable lumen wise with these 80,000mcd LED's

I don't really know anything about Reef Lighting, but it would be really cool if you could integrate a "water cooling" system into the filtration system. I wonder if you could get one of those Water Cooling kits designed for CPUs, and attach it to the heatsinks of the Luxeon Stars, and integrate it with the filtration's flow of water! Might put you over the $200 mark though... :shrug: but you'd have some COOL LED's! (in both senses of the word. :thumbsup
-Allen

I really wanted to avoid luxeons due to cost and heat but will consider it. I want to try clustering these smaler LEDs.

Am I figuring the power needed to run these incorrectly?

25 parallel strands of LEDs/resistors, each leg would have 20mA and 16VDC, so the power supply would need to be 25x20mA= 0.5Amps, or an 8 watt 16VDC adapter.

I really need to make sure I dont screw that part up.

The heat coming from your project is going to be roughly the same whether you use Luxeon, Cree, or 5mm LEDs (for the same amount of light.) The substantial difference is that on power LEDs, they have actually thought about it, and for all of those 5mm LEDs, it is your problem.

I probably would not use a white LED for your application, as the colors might not be quite as intense as your group is used to. I would instead make up a setup with 4 - 5 single color Luxeons in series. (B - Cy - G - A - R). Your 16 V DC supply with 500ma of drive current should be fine, perhaps you can even resistor it down a tad.

If you drive at 350ma instead of 500, you can use Lux Is, surface mount them to a thick area of copper (each separately) and drive them in series. At $ 6 / each, it is not that expensive.

Color rendering will be superb, esp if you add a diffuser.