A zoetrope is a mechanical device that animates a series of pictures by spinning them fast enough that the images appear to merge together and move, My digital zoetrope works on a similar principal, by flashing the LEDs while they are spinning it is possible to display text, patterns and possible even simple animations. My design uses an Arduino Pro mini powered by a system of brushes and a magnet and hall effect sensor for position detection.
I used an Arduino Pro Mini from Sparkfun as the projects controller, the motor is just a small hobby motor which can be bought cheaply or salvaged for free. You'll need 7 LEDs and resistors for them, use resistor values slightly lower than those specified for your LED type, the LEDs will be switching on and off very quickly so they're not at as much risk of being damaged by the current, The resistors I used where too high so the LEDs arn't as bright as they normally would be when it is spinning.
The Hall Effect sensor was bought several years ago so I'm missing its actual parts number but it has an analog output on its middle pin that gives a reading that is proportional to the magnetic field strength on the sensor. I also used a small neodymium magnet to trigger the sensor.
I used two tins to create the base of the zoetrope, the square tin just acts like a case but the round tin lid on top must be conductive as it will be the Arduinos negative supply..