[Swlug] DIY Geiger counter

[Rhys Sage]

Thanks for everybody's responses so far. I think what I'm going to have to do is to experiment.

Reading up on radiation, it seems that the emissions are rapid enough that during any particular sampling session. Using an ATTiny13 with its 1mhz clock speed, the samples should contain enough readings to represent an accurate radiation count.

The interesting thing is that using the ADC on the ATTiny13 I might get not just a frequency count but a strength count. I''ll have to experiment. 

What I'm aiming at is a handheld Geiger counter that can give a good indication of the radiation count in whichever of the count methods I eventually employ. I had thought of using Americium 241 from a smoke detector as my test sample. The problem with that though is that plastic blocks the alpha emissions. My detector crystal is in a plastic housing so probably no alpha reception. I did find out that the Americium 241 is an extremely hazardous substance which could be fatal even in the small quantity in a smoke detector. I don't think 'er indoors has seen an episode of Criminal Minds in which it's used so I'm still safe for the moment.

I was going to use a pair of BC547s, a capacitor and a resistor as the amplifier for the BPX61. Then I read around and the OPA134PA amplifier was recommended as producing less electronic noise though I can't imagine what noise a simple setup of BC547s would produce. 

I do have an oscilloscope though I'm not brilliant at using it due to the lack of information in the Chinese instruction leaflet. 

There are a couple of other ideas I have for the scintillation detector. Once I have the handheld unit working, perhaps a LORA unit though the websites seem to indicate nobody uses LORAWAN nearby. I could also tie it with some of my other ideas/projects. I have the kit needed to use solar power to generate hydrogen from water and I have built a shortwave CW transmitter. Those could be tied together to make a hydrogen balloon that carries a small solar panel, radio transmitter and scintillation sensor then float around the world broadcasting radiation readings, annoying radio hams the world over but providing useful information. I'm not sure how leak proof or practical the big lawn and leaf bags would be as hydrogen balloons but that's all just future thoughts.

For the moment I just want to get the Geiger counter working. At the moment I'm waiting for the paint to quit off-gassing before I put the crystal into the tube and seal it with the photodiode. It should be ready by tomorrow. I'll work on it all over the weekend.

Rhys Sage