Geiger Counter

The basic charging circuit produces in excess of 500V+, depending on the inductor used, leakage of various components, etcetera. The current output is limited by a 10Mohm resistor, which keeps short-circuit current under ~60uA. Thus this is a relatively safe project. The transistors used are by no means sacred; this design can be seen in several places across the web, and no two schematics use similar
Geiger Counter - schematic

transistors. The 2N3904 could be replaced with a 2N2222, the 2N3906 with a 2N2907, and so on. The 2N6517 is rated at 350V collector-emitter, so a substitute NPN transistor should meet these specifications. If in doubt, download some datasheets and see what looks like it will work. All four diodes should be rated for at least 600V. 1N4007`s are common, but anything similar can be used. The 15mH choke is a small, 0. 75" x. 2" diameter epoxy encapsulated inductor with a ferrite core. Anything around this value should work. If all you`ve got is a few 4. 7mH, just put two or three in series. The 0. 01uF capacitors should be rated for 300V or so. Given the low currents involved, this may not be absolutely necessary. For the `voltage regulator`, two NE-2 lamps are used; I`ve seen versions of this which used harder to acquire zener diodes. In my experience, all zeners do is cut down on power consumed by the supply, which here at United Neko is the least of concerns. You are most likely not going to be using this in a post-Apocalyptic world where batteries are scarce. The neons also look a bit more impressive as they gently flicker in their distinctive orange hue. The audio stage is simply an LM386N audio amplifier chip, probably one of the most common out there. If you don`t like this chip (many people do not, and it does give me hell at times), you could use an amp made from discrete transistors. Doesn`t really matter, as long as...

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