[Swlug] DIY Geiger counter

[Daniel Morris]

I'd have thought a depth gauge would be more urgent :‑J

I do hope you're keeping safe.

 Daniel

On Thu, 6 Mar 2025 at 16:34, Rhys Sage via Swlug
<swlug at mailman.lug.org.uk> wrote:
>
> I'm in the middle of a project - to build a Geiger counter. It's a fun project so far.
>
> I have all the bits I need (I think) but as with all projects there's a lot of experimentation and changes made on the fly.
>
> I'm using a Thalium-doped Cesium Iodide crystal in combination with a BPX61 photo diode. For those that don't know- the BPX61 is slightly more sensitive to green light. The crystal emits blue/green light when struck by gamma radiation. Whether it emits light when struck by Alpha, Beta or X-Ray, I don't know. I do know there are other crystals more suited to those.
>
> The BPX61 output will feed into an OPA134PA amplifier and then that will in turn feed into a microcontroller. Given that the events generated by radioactive decay are very brief, would microcontroller speed make much difference? I could use an ATTiny13/ATTiny85 or something small like a micro RP2040 or an ESP32 C3 Super Mini.
>
> With a regular Geiger counter,does the system store the events somehow or does it just rely upon measuring maximum pulses when a pulse happens during a sampling period?
>
> Rhys Sage
>
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