Connecting Geiger Counter for Arduino and Raspberry Pi to radmon.org

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2 months 2 days ago - 1 month 3 weeks ago #4268 by pilovis
I also tested the SBM-20 tube on this device.

Conversion factor for SBM-20 tube.

Russian SBM-20
60Co 1/150 = 0.00664
226Ra 1/198 = 0.00504

Please note that conversion factor varies depending on the tube sensitivity at different isotopes, Cobalt60 and Radium226

Nevertheless, based on my testing compared to the local university lab readings, and based on what Libellum (the company that manufactures the kit) declares here:
www.libelium.com/wireless_sensor_network...els_geiger_counters/
the most appropriate value for SBM-20 tube with this circuit seems to be 0.00277
Last edit: 1 month 3 weeks ago by pilovis.

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2 months 1 day ago - 2 months 1 day ago #4269 by pilovis
based on first data results (to be confirmed with extensive testing), it seems that the SBM-20 tube is much more stable and accurate than the chinese J305β tube the manifacturer is using on this device.

The SBM-20 tube i'm using was bought after the Chernobyl disaster as a spare part of my old russian geiger counter, this tube was abandoned in a drawer for decades :cheer:


Last edit: 2 months 1 day ago by pilovis.

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2 months 1 day ago - 2 months 1 day ago #4270 by pilovis
A very interesting declassified document from U.S. Army Ballistic Research Laboratory about how to perform radiological monitoring in case of incidents involving the release of radioactive materials:

apps.dtic.mil/dtic/tr/fulltext/u2/a207901.pdf
Last edit: 2 months 1 day ago by pilovis.

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2 months 1 day ago - 2 months 1 day ago #4271 by pilovis
After some extensive testing it seems to me that the chinese tube J305B, supplied with this device, is totally unreliable, the CPM reading varies from 3 to 15 without any apparent reason, even if I shielded it from U.V. and Alfa radiations.

By using the SBM-20 tube everything works well and readings are correct and stable.

In my opinion this chinese tube is a sort of piece of junk, like many low cost chinese products :sick:
Last edit: 2 months 1 day ago by pilovis.

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2 months 1 day ago - 2 months 1 day ago #4272 by pilovis
If you want to use the SBM-20 geiger tube instead of the junky J305By default tube, you need to do a little modification on the radiation board:
the C2 capacitor of 1 uF (see image below) should be increased at about 2 uF to higher the H.T. from 370V to 400V to better supply the SBM-20 tube.
Actually the SBM-20 works even at 370V, but obviously 400V is better.

It's enough to solder in parallel to the existing C2 cap another electrolytic cap of 1 uF, be careful with the polarity, on SMD capacitor the line is the + (positive), in the ciclindrical standard capacitor the line is the - (negative).



In case you would need 500V for another kind of tube, the capacitor should be increased up to 10 uF.
Last edit: 2 months 1 day ago by pilovis.

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1 month 3 weeks ago - 1 month 3 weeks ago #4298 by pilovis
Sometimes it may happen that the "measure" process involved in the CPM measurements could die, in that case you will notice "0" CPM readings for long time.
To avoid that I wrote the following script that continuously checks if the "measure" process is running and if not it launches the other script to restart it.

geiger-check.sh
#!/bin/bash
#####################################################################
# Check if "measure" process is running, if not launch the "restart-geiger.sh" script
# -x flag only match processes whose name (or command line if -f is
# specified) exactly match the pattern. 
#####################################################################
# start loop
while [ 1 ]
do
#check if the process is running
if pgrep -x "measure" > /dev/null
then
# if so do nothing
    echo "Running" > /dev/null
else
# if not lauch a script
    echo "Stopped" > /dev/null
    /bin/sh /root/restart-geiger.sh
fi
# wait 30 seconds before doing another check
/bin/sleep 30
# end loop
done

restart-geiger.sh
#!/bin/bash
#
# just to be sure, kill any "measure" process it may be running.
/bin/kill $(ps aux | grep 'measure' | /usr/bin/awk '{print $2}')
/bin/sleep 1
# restart CPM reading processes and send it to background
/bin/sh /root/print_rad2csv.sh &
Last edit: 1 month 3 weeks ago by pilovis.
The following user(s) said Thank You: mw0uzo

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