geiger-muller-tubepower supplystep-up
I have one of these HV dc converters and I was wondering if I can use it to supply a small Russian SMB21 Geiger muller tube. What other parts would I need to add not to fry the GM tube? Keep in mind I would also like to add a nice Arduino nano and display and turn it into a simple Geiger counter.
The step up dc dc converter is a EMCO A series A04P
You have to apply a high voltage, like +500 V DC via 3 or more series resistors to the central anode, and connect the cathode via a 100 k\$\Omega\$ resistor to ground. The HV supply has only to source less than a mA. If an ionizing particle passes through the GM-tube, it will cause a brief discharge current, which in turn will give a brief pulse over the resistor.
You'll need a radioactive source to test it. The higher the radioactivity the more pulses per minute you'll get (and the more unhealthy it is!). The pulses are short, IIRC in the order of microseconds, depending on the kind of particle. You'll need a storage scope to see them, or trigger a monostable multivibrator (MMV) with them, so that they're stretched in time.
Wikipedia has some good examples about dimming. For as simple solution as possible (by electrical terms) I would use a transformer, full wave DC bridge and a thyristor. Again, wikipedia has a great picture of that
Note that thyristor dimmers usually make some radio frequency noise but as I see it, this is one of the simplest AC dimmers.
You will find more info about different dimmers on http://en.m.wikipedia.org/wiki/Light_dimmer
And although you would like to keep out from MCUs, at least think about them. If the thyristor-stuff goes over your head, try to use MCUs. You will find them to be very useful for your future projects.
Best Answer
This site is an excellent reference in everything geiger-countery you might ask. There's a nice schematic which shows the complete circuit, including the power supply and the detection parts:
In general you just need a Mohm-range resistor to limit the current through the tube, and a few transistors/resistors (the "impulse detection" part).
After that it's just simple arduino code (attach interrupt, etc.)