so, as that little 10g salt tank cycled it was obvious that that 18" florescent hood was not going to be enough, and i was itching to play with some of the electronic designs i had been developing for the main tank - so i took a week or so and built a custom LED light for it. low budget and very much from scratch. I also had some 10w LEDs that i wanted to test out.
here is an abbreviated list of the components:
1 stainless steel dog bowl (for reflector)
1 old PC fan and heat-sink
1 12v 2a DC adapter i had lying around
some old phone cable
1 10w 6500k white LED (3 for $12, ebay)
3 3w 445nm royal blue LED's (10 for $15, ebay)
1 ATMega 328 microprocessor ( $3.50, tyda)
1 DS1307 real time clock chip ($2, tyda)
lots of misc electronic parts (resistors, caps,transistors, diodes, plugs, prototype boards,etc (~$6, tyda)
some blue acrylic for the enclosure ($12 for enough to build 3, Tap plastics)
acrylic cement (cost ~$10 plus shipping, but i have used this a lot and barely made a dent in it, Tap plastics)
about 4" of acrylic rod ($1.50 for 6ft, tap plastics)
6 small stainless steel screws (~$3 for a small bag at HD)
so the base idea is this, I built 2 pwm controllable LED drivers, one 1A constant current for the 10W led, and the other 600mA for 3x3w LED's side by side using the same 12v supply. based on the poormans buck driver here:
http://www.instructables.com/id/Poormans-Buck/.
then i added in a 5v regulator, the ATMega, the DS1307 to controll the buck drivers and dim the lights over the right period and at the right time, and a power transistor to control the fan. i had to program the chip in my arduino and then add it to the circuit, as this was a low budget build. a more robust one would include a display and some buttons to set the time and timers. info on how to wire the RTC can be found here:
http://tronixstuff.wordpress.com/2010/05/28/lets-make-an-arduino-real-time-clock-shield/
i had to play with the fading a bit. the microprocessor with arduino code supports 256 levels for PWM, but that doesn't translate perfectly to 256 levels of equal fade. i did some toying and decided on 8 levels i liked - off(0),15,50,90,130,170,210,(on)255.
once the electronics were tested and working it was time to put it all together. i drilled and tapped the heat-sink to mount the LED's. with great difficulty i hacked a big enough hole in the bottom of the dog bowl to mount it to the heat-sink and act as the reflector. and then wired the pendant up with a stretch of the cat3 phone line. i cut and glued together the acrylic to make the electronic enclosure, drilled the holes for wires, buttons, and air flow, then put it all together.
a few modifications - the blue enclosure looked great, but i couldn't tell the difference between my blue and white indicator lights (i know, why need an LED to indicate that your LED is on? - because indicator lights are cool!) so i drilled some holes in the faceplate and added some sections of clear acrylic rod, now it has nice blue and white indicator lights (that you can tell the difference between)to indicate which color channel is active. I downgraded the PC fan to 5v. it was running at 12v, but was loud. at 5v you cant hear it at all, and the heat-sink still doesn't get warm.
comments: its very bright. perhaps too bright for a 10g, but i'm still toying with it - i only have a few mushrooms and polyps and softies, and the water isn't perfect (hard to keep it perfect in such a small tank, salinity jumps around a bit and im struggling with getting the phosphates to 0 (seems to like to hang out at ~.2ppm)). my first coral in there is a eagle eye zoa, and it never has fully opened. it opens about 70%. its healthy, and has even budded off 2 new polyps, but none of them open as full as it was in the tank where i got it. I adde a few more polyps and softes last week and they seem to be thriving, so perhaps its just that one.
anyway, here is a pic of the light and the tank:
I'll def be following this thread. Great job on the tank stand too!