This instructable builds on top of the Geiger counter triggered LED decorations I made last year. This version powers the Geiger counter from the Arduino (itself now powered from a mains adaptor, so I no longer need to keep feeding them batteries) and the LEDs now fade in and out for a more gentle effect.
Detect particles and/or make a cool random number generator with this handsome Geiger counter kit. This easy-to-make pack of parts turns a simple Geiger-Muller tube (included) into a portable blink, beeping radiation detector. You can also connect an FTDI friend to the header, to get serial output for datalogging on your computer.