[Swlug] DIY Geiger counter

[Rhys Sage]

My 10M resistors finally arrived. I'd ordered a set from AliExpress and in the hope of getting them faster, also from eBay. It turned out the 10M 5% resistors from eBay were about 17% out of line at 12.4M. My AliExpress resistors were 10M 1% and they were also out of line. The one I'm using is 9.82M so, reasonably close.

I also ordered a boost converter and set that to 27v exactly as per the writeup in the journal. Results look better. My test sample is a Tritium capsule. That might arrive tomorrow.

What I expect to see is peaks on the scope when I bring the tritium source close by. Thus far I have not shielded the circuit. I'll try wrapping the circuitboard in paper and then bacofoil at some point. I want to try the tritium capsule next.

Since work has slacked off a bit at the moment and my middays are free from 8:30 til 1:15 I might get something done in the lab as soon as the tritium arrives.

I've added photos of the scope readout, both sides of the circuit board and the circuit, The black/white wires are +/- from the 27V boost converter which runs off a PP3 battery. The yellow/green wires go to the BPX61 photodiode. The blue/white wires go to the scope or to an Arduino (eventually).

Having to order stuff from China takes an age and does curb enthusiasm. I dragged my feet all day over going to the lab to build the circuit,almost convincing myself that it was never going to work and that I should work on 'er indoors pickup truck instead.

Rhys Sage
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