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I'm attempting to create my own Geiger-Muller counter based on an old, soviet STS-5 tube.

I want it to be as compact as possible. I don't want to use ready-made modules, like this one, instead I want to put everything on one PCB. My only struggle concerns the high voltage part. I want the circuit to be as compact as possible, hence I wonder if there's a simpler, more compact option to bring, let's say 9V to the required 400+ V DC. Using a simple transformer and a MOSFET to switch the 9V on primary would be the easiest method, but maybe there is something better, more compact, that I have no knowledge about yet?

Chetan Bhargava
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sp9dev
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    What current does it need to supply? A photoflash circuit may work well for that, although you'd need one modified to work off of a 9V tube rather than 1.5V. More generally, you want a flyback circuit. – TimWescott Nov 01 '19 at 21:15
  • @TimWescott From what I understand, the tube does not draw more than around 7mA during a peak (detection of a gamma particle, very short time) and in the microampere range while idle. I found a circuit like that: https://www.theremino.com/wp-content/uploads/2012/02/GeigerAdapter_Datasheet_ENG.pdf On page 8 a schematic diagram is shown, and from what I can understand it indeed uses a flyback circuit. – sp9dev Nov 01 '19 at 21:26
  • That's not quite a flyback -- it looks like someone left a Cockcroft-Walton multiplier in a room with a boost converter, and allowed them to breed. But it should do the job. Actually, if you use a real 40106 and not the 74HC equivalent, you may be able to get away with using that power supply circuit. – TimWescott Nov 01 '19 at 21:52
  • @TimWescott Would you consider the circuit presented here on page 18 a better approach? https://serwis.avt.pl/manuals/AVT3074.pdf – sp9dev Nov 01 '19 at 22:00
  • I like your first one better, because the voltage on the transistor is lower, it's regulated, and the multiplication ratio in the boost is lower. But that's just an opinion -- "better" depends on what you want. There are photoflash driver chips that will regulate the output voltage; on a super-zoot circuit, they would be "better", but you'd need to get the right transformer. – TimWescott Nov 01 '19 at 22:13
  • Keep in mind that 7mA at 400V is almost 3W so significant draw at 9V, maybe 350 or 400mA. Otherwise your high radiation reading may be limited by the power supply. Of course given the lack of sensitivity of those tubes, you probably won't have long to complain. – Spehro Pefhany Nov 01 '19 at 23:06

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Could be a duplicate to this: geiger tube dc power supply.

The supply listed there works well, I can attest to it (and the guy has sold hundreds of working Geiger Counters, using SBM-20 or SBT-5 tubes).

Of course as you want to make it compact, you should redesign the PCB to use small SMT components as opposed to the TH ones used in the kit.

anrieff
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