Geiger Counter - Radiation Sensor Board for Arduino and Raspberry Pi
Concerned or curious about radiation leaks? This small, portable, lightweight Geiger counter works with a free downloadable app for your iPhone to precisely measure beta and gamma rays from microsieverts per hour.
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Geiger Counter Kit - Radiation Sensor
Build Your Own Geiger Counter
Here's a more sophisticated Geiger counter, with a windowed tube that can detect alpha radiation as well as a USB output.