When you believe of a radiation detector, you’re most likely believing of a Geiger tube as well as its high voltage circuitry. That isn’t the only method to determine gamma radiation, though, as well as [Alan] has a fantastic circuit to determine even fairly weak radiation sources. It utilizes a extremely little photodiode, as well as draws so bit power it’s ideal for jobs with the smallest power budgets.

The detector circuit utilizes a miniature solar cell and a JFET wired up in a little brass tube to block many of the light as well as to offer some EM shielding. This, in turn, is connected to a little amplifier circuit with a LED, Piezo clicker, as well as in [Alan]’s situation a little counter module. The photodiode is really sensitive sufficient to spot the little amounts of gamma radiation created from a smoke alarm americium source, as well as likewise registers [Alan]’s other much more powerful radioactive sources.

The circuit only draws about 1mA, however [Alan] states he can most likely get that down to a few micoAmps. A ideal radiation sensor for lightweight as well as low power applications, as well as provides us the motivation to put a high altitude balloon job together.