Moodlamp
Here is my latest project: a simple moodlamp using a Prolight 3W RGB LED emitter. The LED itself comes on an aluminium star, but i needed to build a bigger cooler made out of an aluminium profile (usually used for rack mounting). I used two screws to fixate the LED on the aluminium sheet.
Without an additional cooler the LED will get very hot after a short while.
The electronics are very simple, an ATmega8 running at 20 MHz on breadboard. Three FETs to drive the emitters and three current limiting resistors. I first used a voltage regulator, but then i figured that the switch mode power outlet would already deliver enough current… but at a very poorly regulated voltage: I set it to 4,5 Volts and measured 5,6 Volts at the output, even under full load. Good thing i added a diode there to limit the voltage a bit so it doesn’t go higher than 5,5 Volt.
The source code is quite simple, it’s running through the HSV color space (not using V though, it’s always 1). You can adjust the speed the hue is increasing and you can adjust saturation using the two potentiometers.