With all the focus on biological problems, we might forget that sometimes it’s handy to know about radiation hazards, too. [Ryan Harrington] shows us how to make a Geiger counter with very few parts, and you can see the results in the video below.

The glut of surplus Russian tubes has made this a common project, but we were amused to see the main part of the high-voltage supply was gutted from a cheap electronic flyswatter sourced from Harbor Freight. Even without a coupon, it only costs about $4.

There’s also a stack of zener diodes, a transistor, and some resistors. A battery, a piezo speaker, and a switch round out the bill of materials. Even then, the switch was upcycled from the flyswatter, so there’s not much to buy.

We see these flyswatters on deep sale sometimes, so maybe next time we do we’ll stock up. You could probably use the high voltage module for other projects, too. The module puts out enough voltage that it needs 400V worth of zener diodes to clamp it. [Ryan] used four 100V zeners.

The transistor causes the speaker to click. Apparently you can omit it, but the clicking becomes much harder to hear. Even with no radioactive material around, you’ll hear clicks occasionally from background radiation. But if you get the device near a smoke detector or a lantern mantle, you should hear a lot more clicks.

This reminded us of another cheap build with a camera flash. Want something more complex? Try this one.


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Muhammad Bilal

I am highly skilled and motivated individual with a Master's degree in Computer Science. I have extensive experience in technical writing and a deep understanding of SEO practices.

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