https://github.com/thedocdoc/Pocket-Geiger-Type-5/tree/main

A solid state low power Geiger

A Geiger counter built from a type 5 Pocket Geiger Radiation Sensor from Radiation Watch. The prototype was calibrated by a known Cesium 137 source and was found to be spot on.

Sensor - https://www.sparkfun.com/products/14209 Note: This product is for educational purposes and should not be directly relied upon for determinations regarding one’s health or safety.

Example output-

Display acknowledged. 
Counts Per Minute (CPM): 1859.00 Radiation (uSv/h): 35.05
Counts Per Minute (CPM): 1867.00 Radiation (uSv/h): 35.21
Counts Per Minute (CPM): 1862.00 Radiation (uSv/h): 35.11
Counts Per Minute (CPM): 1870.00 Radiation (uSv/h): 35.26