Christine J

Member Since: March 13, 2011

Country: United States

  • Product SEN-09848 | about 3 years ago

    I took a closer look at this design and I have a few questions.
    First, the geiger tube is specified to operate at 500VDC, with a range of 450V-650V. My measurement of the Sparkfun board yields 251.5V, half the nominal voltage. This drive voltage is far outside the specification of the geiger tube, and so one cannot depend upon the specifications of the part. (the specs of the geiger tube are actually quite good. It is exceptionally linear for many orders of magnitude difference of radiation). My question is: have Sparkfun folks actually measured a calibrated radiation source?
    Second, the transistor Q4 is being driven without bias from an AC-coupled source (the geiger tube), and my measurements show the base is being driven to -12VDC when there is an event, but the reverse breakdown voltage for the base-emitter junction of a MPSA18 is 6.5V. It seems to me a clamping diode is required.

  • Product SEN-09848 | about 3 years ago

    If I can just put in my $0.02 worth: I think it might be better to create a new version of firmware that outputs via USB the number of counts per minute, each minute.
    For my implementation, I used a Basic Stamp 2. I picked off the OUT signal off the header holes on the edge of the board. I then count the number of events in a minute, and send that number to my linux box via a RS-232 serial port. I also modified a few perl scripts to calculate the average CPM over the course of an hour and automatically upload that data to twitter via ttytter.
    I can give more details if anyone is interested.

  • Product SEN-09848 | about 3 years ago

    Here is some hourly averaged data from Alsea Oregon over the last few days:
    Date hh:ss Average CPM
    2/17/2011, 19:00 28.7
    2/17/2011, 20:00 29.2
    2/17/2011, 21:00 29.1
    2/17/2011, 22:00 26.6
    2/17/2011, 23:00 24.1
    2/18/2011, 0:00 27.2
    2/18/2011, 1:00 27.4
    2/18/2011, 2:00 28.3
    2/18/2011, 3:00 29.1
    2/18/2011, 4:00 29.9
    2/18/2011, 5:00 28.2
    2/18/2011, 6:00 29.0
    2/18/2011, 7:00 29.2
    2/18/2011, 8:00 30.1
    2/18/2011, 9:00 29.4
    2/18/2011, 10:00 32.3
    2/18/2011, 11:00 27.9
    2/18/2011, 12:00 30.0
    2/18/2011, 13:00 29.2
    2/18/2011, 14:00 30.5
    2/18/2011, 15:00 32.0
    2/18/2011, 16:00 29.1
    2/18/2011, 17:00 28.6
    2/18/2011, 18:00 27.7
    2/18/2011, 19:00 28.1
    2/18/2011, 20:00 28.7
    2/18/2011, 21:00 31.7
    2/18/2011, 22:00 27.7
    2/18/2011, 23:00 29.1
    2/19/2011, 0:00 27.8
    2/19/2011, 1:00 29.7
    2/19/2011, 2:00 30.5
    2/19/2011, 3:00 29.2
    2/19/2011, 4:00 31.0
    2/19/2011, 5:00 31.1
    2/19/2011, 6:00 29.9
    2/19/2011, 7:00 33.4
    2/19/2011, 8:00 29.0
    2/19/2011, 9:00 31.6
    2/19/2011, 10:00 31.3
    2/19/2011, 11:00 32.5
    2/19/2011, 12:00 28.5
    2/19/2011, 13:00 31.6
    2/19/2011, 14:00 29.2
    2/19/2011, 15:00 31.5
    2/19/2011, 16:00 29.2
    2/19/2011, 17:00 28.2
    I also setup a twitter feed called AlseaORGeiger if anyone is interested in monitoring the feed.

  • Product SEN-09848 | about 3 years ago

    I was surprised there were any left when I ordered.
    I’m in the Central Coast range of Oregon, not too far from Corvallis. I will post data tomorrow, but a first test yielded 820 events in 30 minutes, or about 27 CPM. Folks can also look at http://www.radiationnetwork.com/ for levels in their location.
    I’d also be interested in software to feed twitter if someone is feeling creative. I might hack something together myself though.

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