Mightyohm Geiger counter online (via serial com port)
Posted: Thu Apr 18, 2013 2:46 pm
I have setup an online display of counts per minute from my Mightyohm Geiger Counter for background radiation, from Victoria Australia. I am interested in seeing if there are any long term trends, there is virtually no risk of fallout here, the nearest nuclear reactor is thousands of km away. The graphs can be found here:
http://www.chankly.com/geiger/cpm.html
and converted to uSv:
http://www.chankly.com/geiger/usv.html
Graphs of last hour, 4 hours, day, week, etc. Uploaded every 5 minutes (or hourly for the longer time ranges).
There were three aspects that may be of interest to the forum.
1) I used a serial com port converter rather than USB serial port as I preferred not to have to install a driver, when a com port should do the job. See photo attached of the converter (the USB connect is used for power only).
2) I power the Mightyohm from the 5V rail of the serial port converter, and I just used 3 signal diodes in series to reduce the voltage to 3V. This works fine as the current drawn is very low.
3) I pass the serial output from the Geiger counter to a log file, and then parse this log file a line at a time to collect the counts each second. These counts are then accumulated for one minute and stored in an rrdtool database (which provides the graphs). Modes supported are SLOW and FAST, as both provide similar output and I was able to test both. This conversion is done by a perl script. I chose to accumulate the 1 second counts in the perl script; though it would have been easier to take the CPM from the Mightyohm output. The reason I chose to do it that way is that I did not understand the FAST/SLOW mode displays both provided the same CPM information until after I did some testing of the script. This is all running on a Linux PC.
If there is any interest I can provide the perl script, instructions for Linux, rrdtool db configs, rrdtool graph definitions, and any more details required.
Regards, Alan F.
http://www.chankly.com/geiger/cpm.html
and converted to uSv:
http://www.chankly.com/geiger/usv.html
Graphs of last hour, 4 hours, day, week, etc. Uploaded every 5 minutes (or hourly for the longer time ranges).
There were three aspects that may be of interest to the forum.
1) I used a serial com port converter rather than USB serial port as I preferred not to have to install a driver, when a com port should do the job. See photo attached of the converter (the USB connect is used for power only).
2) I power the Mightyohm from the 5V rail of the serial port converter, and I just used 3 signal diodes in series to reduce the voltage to 3V. This works fine as the current drawn is very low.
3) I pass the serial output from the Geiger counter to a log file, and then parse this log file a line at a time to collect the counts each second. These counts are then accumulated for one minute and stored in an rrdtool database (which provides the graphs). Modes supported are SLOW and FAST, as both provide similar output and I was able to test both. This conversion is done by a perl script. I chose to accumulate the 1 second counts in the perl script; though it would have been easier to take the CPM from the Mightyohm output. The reason I chose to do it that way is that I did not understand the FAST/SLOW mode displays both provided the same CPM information until after I did some testing of the script. This is all running on a Linux PC.
If there is any interest I can provide the perl script, instructions for Linux, rrdtool db configs, rrdtool graph definitions, and any more details required.
Regards, Alan F.