Brigadoon - An Occasional Corner on the Internet
Geiger Counter
Designed by Mark Little
 
The Geiger Counter was built from a Geiger Counter kit available from Oatley Electronics. The kit was mounted in a case and the battery pack replaced by a regulator that allows the kit to run from +12V.

An open collector output is provided as the output of the PCB. Currently, this output feeds the speaker as per the kit, but later it will be fed into a counter than will be used to record the particles detected.
The background radiation normally detected by this device is about 20 pulses per minute. The pulse tend to come in bursts, rather than at a constant rate, so the background radiation reading need to be averaged over a long period.