For my next trick I thought it would be nice to have a web interface “colour wheel” to control an RGB LED strip light. These are dirt cheap and usually come with a crappy infrared remote control. The real nice part about this is once you have it working you can do almost anything you want with it – make a gradual sunrise light for the dark mornings, a security light, an auto-off night light or simply pick the colour you want your room to be from a smart phone.
The basic idea of this design is to have the Arduino handle the control of the LED strip itself but allow the RGB values to be set via a serial connection. The Pi will be sending the RGB values via USB to the Arduino which in turn will use Pulse Width Modulation (PWM) to set the intensity of each LED.