|CHOUR - Very low power Geiger Muller counter PC-GM3|
Device : Geiger counter
Date : 2013-2015
Type : PC-GM3
Brand : Chour
Main parts: GM Tube SBM20, MSP430 Texas Instrument family processor, Imex module for High Voltage, RTC PCF84583
Main characteristic : Average power consumption around 20µA.
Software : Downloading.
Power consumption :
- In normal mode (running with battery, ground radioactivity, no alarm, no dialog...), the average power consumption is round 20µA.
- high voltage generator available on e-bay in 2015. IMEX-38-56-1 French documentation.
- A development board from Olimex based on Texas Instrument MSP430f449
- A Russian Geiger tube SBM20.
- a battery charger.
- a communication module USB-RS232 TTL
Inside the counter.
The functionnal specification (in French) are available here.
I consider that the Olimex module MSP430f449STK2 has a bug. Indeed, you cannot use the bargraph as a bargraph. You can fix this bug with these modifications (see the schematic below).
- Remove the resistors R9 and R10 (0 ohms).
- Cut the pin 42 and 35 of the LCD display.
- On the PCB, connect 42 with 40 and 35 with 37.
The software of the counter has a constant to generate two versions of the executable. A version uses the bargraph as an alert indicator (PCB not modified), the other uses the bargraph as a rate indicator of the counting.
Available on downloading page.
The Geiger counter under development. Below a trace of I2C communication.