PROJECTS: GEIGER COUNTER
makeprojects.com/v/29
3. TUNE THE COUNTER
Turn on the Geiger counter and if you have a
radiation source, bring it close to the GM tube.
Now simply adjust potentiometer R6 until
you hear clicking and see the LED blink. Each
click and flash represents the detection of
one alpha, beta, or gamma particle passing
through the tube (but not all such events are
detected; it depends on the tube’s sensitivity).
Without a radiation source, background
radiation from natural sources on Earth and
cosmic rays will cause the Geiger counter
to click. Where I live, background radiation
triggers about 16 counts per minute (CPM)
with an LND 712 tube.
That’s it — you’ve made a Geiger counter!
The terminal block in the corner of the PCB
has 2 pairs of output contacts for connecting
to other devices: +3V–5V digital pulse signal
(labeled “D” on the board) and ground
(labeled “G”).
3
STEPS 4 THROUGH 6 ARE OPTIONAL. They explain how you can connect your Geiger counter’s output
to a portable data logger, an analog meter, a digital display with serial output, and the Radiation Network,
a public database that pools data from radiation monitoring stations worldwide.
4. CONNECT A DATA LOGGER
4a. Connect a 9V battery to
the EL-USB- 5 logger and plug
the logger into a free USB
port on your PC. 4a
4b. Run the installation CD,
and select the Set Up and
Start option. In the Name/
Mode of Operation screen,
select Count Events, and on
the next screen, set the trigger to “Rising edge” voltage
and the LED flash to Off.
4b
4c
4c. For Voltage range, specify
0V–3V. The board outputs
4V–5V, but the data logger
loads this output down to
about 2.8V.
In the Time Period screen,
choose 1 minute. Continue
through the rest of the installation wizard, which is all
self-explanatory.
106 Make: makezine.com/29
NOTES: For logging
radiation data from the
field with a small, portable
setup, I’ve used the EL-
USB- 5 Data Logger from
Lascar Electronics.
You can also use a smart-
phone with a data-logging
application.
You can specify a different
increment than 1 minute,
but note that the logger can
count up to 32,510 events
per period, at a maximum
data rate of 100 events per
second (with the LED off).
Gregory Hayes ( 3)
