Bunnie Huang, cracker of the Xbox and creator of the Chumby, wanted to do something to help people in Japan following the Fukushima Daiichi disaster. He created a reference design for a cheap, reliable, stylish Geiger counter for everyday carry, under the auspices of Safecast, a group that works on ongoing disaster relief in Japan. Being a consummate hardware hacker, bunnie has documented the steps he took along the way to create his free/open Geiger counter.

After much discussion and review with the Safecast team, we decided that a key component of the user experience should be a graphic display, instead of a 7-segment LED readout. Therefore, a 128×128 pixel OLED panel was incorporated into the design. The OLED panel would be mounted behind a continuous outer shell, so there would be no seams or outward design features resulting from the introduction of the OLED. However, as the OLED is not bright enough to shine through an opaque white plastic exterior shell, a clear window had to be provided for the OLED. As a result, the naturally black color of the OLED caused the preferred color scheme of the exterior case to go from light colors to dark colors. User interaction would occur through a captouch button array hidden behind the same shell, with perhaps silkscreen outlines to provide hints as to where the buttons were underneath the shell. I had originally resisted the idea of using the OLED because it’s very expensive, but once I saw how much an LND7317 tube would cost in volume, I realized that it would be silly to not add a premium feature like an OLED. Due to the sensor alone, the retail price of the device would be in the hundreds of dollars; so adding an OLED display would help make the device “feel” a lot more valuable than a 7-segment LED display, even though the OLED’s presence is largely irrelevant to the core function of the apparatus.

Safecast Geiger Counter Reference Design