[Swlug] DIY Geiger counter

[Rhys Sage]

It's the middle of my Friday workday. I've just done the 5:45 - 9:45 session and I'll go back for the rest in about 3 hours.

Sad to hear about your tree. I hate it when they chop trees down and here I've seen literally hundreds of acres of pine and assorted other trees vanishing underneath new shopping and residential estates. All of them are poorly built, largely from OSB and everything is built on sand. No proper foundations at all. American building, plumbing and electrics are laughably low quality.

I use ChatGPT to do what it does best - as a database. I fed it my list of semiconductors and asked it which was the fastest. Then after it told me the BC517 was, I pulled out my semiconductor book and checked the specifications just to make sure ChatGPT wasn't doing what it's also very good at - giving erroneous results. It is hard to fathom why they didn't feed it only accurate, verified data - they had to know at the back of their minds that feeding it random websites would bias the results. 

I looked at the 30,000 times gain of the BC517 versus the 110 times gain of the BC547 which I presume being used as a Darlington pair would result in gain of something like 10,000 with probably 10% loss.

I'd never heard of the Sziklai Pair. It sounds interesting. I'll see what I can do with the BC517 though.

The current plan is to put the BC517 on the BPX61 all powered by 4.7v from my adjustable buck converter then put the output into an ATTiny13 or an ATTiny85 with output from that going to a piezo speaker and a 1627 display module. I could be a hero and use 3 LED digits and some shift registers but I'd rather do it the easy way.

The 3-pronged figure is probably the symbol for a Geiger Muller tube. That circuit seems to use a 30v supply for the tube which seems a little low given that most need 350v. Perhaps they have a special low-voltage tube?

I played with ChatGPT some more and it came up with a circuit diagram that looks a bit bizarre. It gave me a monospace diagram:
          +4.7V
            │
            ├───────────────┬──────────┐
            │              ===         │
           10kΩ           100µF        │
            │              │           │
   BPX61    │              │           │
   ┌───┐    │              │           │
   │   │    │              │           │
   │  ─┼────┴───┬───┬──────┘           │
   │   │        │   │                  │
   └───┘        │  1kΩ                 │
      │         │   │                  │
     === 10nF   │   │                  │
      │         │   │                  │
     GND       ┌┴┐  │                  │
               │ │  │                  │
               └┬┘  │                  │
                │   │                  │
                │   ├──────── Signal to Arduino (Interrupt Pin)
                │   │
               ┌┴┐ === 10nF (Pulse Shaping)
               │ │  │
               └┬┘  │
                │   │
               GND  GND

That just looks a bit odd to me. 

Well, I'm back off to work now. It's got a bit warmer now - it was 50F so I was wrapped up warmly this morning. It's now 76F so I'm in a tee-shirt. This is the kind of weather when you have the car heat on in the morning and the AC on in the afternoon.

Rhys Sage