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I'm currently making a geiger-counter and therefore I need to crank my 5VDC up to around 400 VDC, the current is very low, around 0.015-0.02 mA. What would be the best way to generate 400VDC from my 5v source?

Anindo Ghosh
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Majorleq
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3 Answers3

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A MAX641 with a suitable FET, see for example this circuit of a Geiger counter (p 34/39).

Incidentally, one of my current projects is to build a Geiger counter for LEGO Mindstorms NXT with a Soviet SBM-20 tube, which needs 400V and at most 50µA. The power supply is 4.3V at 20mA, and I plan to use a MAX641 with a BSP126 or BSP130.

There is also this thread (in german) about circuits for an SBM-20.

starblue
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Maxim has a design for a G-M tube power supply that takes a 5V input:

http://www.maxim-ic.com/app-notes/index.mvp/id/3757

It looks easy to make, and should be quite cheap and very compact.

Leon Heller
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  • Interesting, I will definitely have to try that. – Majorleq May 21 '11 at 17:13
  • +1 because it's a nice hobbyist's approach using a simple inductor and really just standard parts. I think even the operational amplifier could be replaced with a 324 or something similar, because I guess the thing need not be super precise. Using a step-up configuration with an auto-transformer might be built smaller and with better efficiency, though. – zebonaut May 21 '11 at 17:28
  • A suitable auto-transformer is going to be tricky to design, and expensive. – Leon Heller May 21 '11 at 17:34
  • With a few modifications the Maxim op amp and reference in that design could be replaced with a TL431, making the circuit even cheaper. – MattyZ May 22 '11 at 20:48
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Here are plenty of designs to choose from, with or without microcontrollers, most producing 400V out of 5V or even less: http://www.pocketmagic.net/2012/10/diyhomemade-geiger-counter-2/

And here is a portable dosimeter: http://www.pocketmagic.net/2012/12/diyhomemade-portable-radiation-dosimeter/

And a geiger muller based radiation monitoring station, operating since October 2012 continuously: http://www.pocketmagic.net/2012/10/uradmonitor-online-remote-radiation-monitoring-station/

Simpler , but not so good, a very basic geiger clicker schematics (just for didactic purposes): http://www.pocketmagic.net/2012/01/diyhomemade-geiger-muller-clicker-v2-0/

A few details on the operation:

  1. Microcontroller version: The uC generates a PWM signal that is fed to the driver transistor that controls the coil. The output is rectified and then measured via a voltage divider and one of the uC's ADC port. By doing so we can then adapt the PWM for the exact voltage value we are interested to get, in this case 400V. This basic mechanism assures a perfectly regulated supply, while keeping ripple to a minimum.

  2. Non-microcontroller versions: An Armstrong oscillator with a blocking transistor that is commanded by a set of zenner diodes, selected to match the desired output voltage. When the voltage exceeds 400v, the blocking transistor kicks in, and the oscillation stops. By doing so, we get a regulated supply, but the ripple voltage is not as good as in the case of the microcontroller version. Nevertheless this is a very simple and easy to build inverted.

PeterJ
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radhoo
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  • Hello radhoo! While the links are interesting, it would be better if you added some information in the answer as a summary. It would improve both the usefulness and the "popularity" of your answer. Also, be moderate in linking to your blog, it might be considered self promotion. – clabacchio Jun 10 '13 at 12:31
  • hey clabacchio, thanks for your suggestion, I added more details on the functionality. As per the many links, there is nothing I can do, I have many projects related to the question, hence there are also many links. cheers! – radhoo Jun 12 '13 at 13:57