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Ok, my “first” Arduino project was a simple mood light. I had previously plans to make this using ATTiny2313, but since I got Arduino Duemilanove from work to play with I decided to do the implementation with it.

The software is so simple that I won’t bother to give any in-depth view about it – it’s basically just driving the PWM outputs on Arduino with analogWrite() in a sequence. I will, hovever, be adding PC control over serial link to it later on so I can decide what colour I want to see on the lamp – like poor man’s PAR spots. Maybe I’ll do also a DMX control but that remains yet to be seen. :)

A while back I got my hands on some standard 5mm common-cathode RGB leds. Since they’re not superbright, I needed to hook up multiple leds to get decent light. This meant that I couldn’t hook very much of them directly to the Arduino, so I decided to build a simple driver circuit for them from BJT transistors. FETs would probably be a better solution, but I didn’t have any at hand while building this so I ended up using BD138 PNP transistors for switches. They can handle 3A current in PWM usage each so it’s more than enough for a huge array of leds, at least in this case, where I use 30mA current for each anode. In fast maths that means I can drive 100 RGB leds with three of them, one BJT for each color, though for now I’m using only four leds. In future versions I’m adding a second RGB driver since there’s still available PWM lines in my board and I’ll also bring the total led count up to 50. I’m also making a PCB for the light once I find a suitable casing for it. Might as well go shopping for it right now…

And last, a nice trick you can do with LEDs that have clear housing – sand them a bit, you’ll get much wider angle and smoother light when using RGB leds and color mixing them :)

Hey-ya. Finally I managed to kick myself in the butt enough to start this site. Maybe it’s because I got some drive into making some hacks, thanks to AltParty, last weekend. I also managed to persuade some folks at work so we got 4 Arduino Duemilanoves for pla.. evaluation. I actually have one of them here next to me right now driving some RGB leds as a moodlight. What a nifty little board! Big thanks to sivu at Paeae Technologies for bringing those finally to Finland!

More stuff coming up.. like moodlight schematics and maybe I’ll show how to play Bubble Bobble theme on Arduino ;)