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