Picture of Star Jar Geiger counter triggered LED decoration (2012 remix)
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.

What you'll need:

    A Geiger counter with pulse output (I'm using the Gieger counter from MightyOhm)
    A few strings of battery-operated LED decorations (I'm actually using USB-powered strings of stars from Poundland - you want something that'll comfortably run off 5V)
    Arduino-based microcontroller (I'm using an UNO)
    Female header (three sockets' worth)
    Male header (I used an 8 pin run)
    5V power supply for your Arduino (this will also power the Geiger counter)
    Assortment of connecting wires (I used a combination of multi-core, ribbon cable and solid core)
    Soldering equipment, wire cutters, wire strippers etc.
    Insulation tape or heat shrink
    Arduino IDE and an USB cable to connect to your microcontroller
    A jar or other receptacle to put the LEDs in

I'm also assuming you've read the original instructable - if not, now might be a good time to do so!