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6406Re: [GPSL] Geiger Counter

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  • James Hannon
    Feb 1 5:57 AM
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      I really believe that the Geiger tube in the electronic goldmine kit is self quenching and does not need any external power supply manipulation to properly quench. What appears to be the tube is on this page http://www.imagesco.com/geiger/geiger-counter-tubes.html It is listed as having a fill gas of Neon, Argon and Bromine. Bromine is the quench gas. All a self quenching tube needs to operate properly is a steady HV supply within the plateau region of the tube and a high value series resistor.
      Here is another power supply circuit. I like this one because it is adjustable but it does have a lot of parts. http://pdfserv.maxim-ic.com/en/an/AN3757.pdf

      Jim Hannon

      -----Original Message-----
      From: "Mike Manes" <mrmanes@...>
      Sent 1/31/2010 9:52:41 PM
      To: "L. Paul Verhage" <nearsys@...>
      Cc: GPSL@yahoogroups.com
      Subject: Re: [GPSL] Geiger Counter

      Hi Paul,
      Looking over the SparkFun device, I don't see any means for the uP to
      control the G-M tube HV bias; Q1-Q2 comprise a free-running ~50 Hz power
      oscillator driving a step-up xformer that feeds a voltage tripler,
      D2-D4.  G-M tube discharge current is limited by R7-8 (11 meg).
      The R7-8 x C6 time constant is about 110 ms, which is a lot longer
      than the G-M tube quench time.
      But I think you have a good idea to use the uP to control the HV
      supply.  Not sure I've seen that approach taken before.
      BTW, I still think you should run it thru your altitude chamber
      before flying it.  Corona discharge could as a minimum ruin your
      data, if not your hardware.  I've seen it happen!
      73 de Mike W5VSI
      On 1/31/2010 19:33, L. Paul Verhage wrote: > > >
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