With this kit, you’ll build an SLM for much cheaper than you can buy one. As seen in MAKE Volume 10.

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).

My daughter and I had fun making the solar-powered fan, electric car, and other projects. She’s a bit young for the kit, so as she used various bits to decorate a finish line for the solar car, I experimented with what else I could power, and for how long, with the 6-farad supercapacitor — those things are amazing. One recommendation: add your own alligator clips (without the leads) to make the solder-less joints less tweaky.