MAKE contributor John Iovine has been designing and improving affordable Geiger counters for decades. After Japan’s nuclear crisis last spring, his company was swamped with orders. Now they’re working on even better designs and DIY kits.

This analog counter detects beta radiation above 36 kilo-electron volts (keV) and gamma above 7keV, signaling each radioactive particle detected with an LED flash and a click in the headphones. For digital output, logging, and graphing, add the DMAD-03 digital meter adapter kit ($60).