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faker-counter

A prop Geiger counter.

This is a fake Geiger counter I used as part of my Halloween costume in 2023. I went as "Oppenclimber", a mashup of J. Robert Oppenheimer (suit & tie, fedora, pipe, security badge, radiation goggles) and a rock climber (climbing harness & gear). I also carried this device, which has a speaker that plays actual digitized sounds of a real Geiger counter at two different levels: a "background" level of a few quiet clicks, and a "high" level of crazy clicks; the level is controlled by a somewhat-inconspicuous button that you push while pointing a "sensor wand" that actually does nothing. It also has two LEDs - green and red, for low and high levels - and a little analog voltmeter whose needle swings in accordance with the clicking.

Hardware

  • CircuitPython microcontroller (needs to support I2S for audio - 3 GPIO pins)
    • The prototype, on a solderless breadboard, used an Adafruit Feather RP2040.
    • The second, final, version used a Raspberry Pi Pico.
      • The only downside to the Pico is that the onboard storage was so much less, I had to create downsampled versions of the audio files. Which still sounded fine - you don't need much bandwidth for a bunch of clicking!
  • 3 watt I2S audio amp, such as an Adafruit MAX98357A
  • Push button to increase click rate.
  • Surplus analog voltmeter, 5 volts full scale.
  • Green LED for low activity, red LED for high.
  • Small speaker. I used an Adafruit 3W 4 Ohm speaker
  • 3 resistors, 1 diode, 1 capacitor (see schematic below).
  • A box; I used a second-hand cash box.
  • Some kind of speaker grill to hide the hole in the box. I used a piece of open-cell foam.
  • USB battery pack.
  • Old broken non-contact voltage tester as the "sensor".
  • A nice braided USB cable as the "sensor" cable.
  • Stickers! I also created artwork which I then printed at a local photo kiosk and glued them on.
  • Solderless breadboard & leads, or "perma-proto" board & solder.

Circuit Diagram


Software

CircuitPython (version 8.2.7 used), of course! Plus the code included here. There are no additional Python libraries to install!

Finished Project









References, Notes

  • Thanks to Paul Price for the VU circuit.
  • It's not as loud as I'd like. In my Halloween party setting, it was just loud enough.