LND712 Geiger Counter Data Logger with LND712 Tube
This is a very compact design that uses a modern LND712 counter Tube. This kind of tube is also widely used in modern commercial geiger counters, and its alpha sensitivity is also a very nice to have feature. The only drawback is its price, I paid around 100 Euros for it....
The high voltage generation is done by a nice little circuit I found in an application note provided by Maxim. It is a very efficient Low Power Design that only draws several microamperes.
The signal from the counter tube is fed through a small transistor stage, this stage provides interfacing to the 3.3 Volts processor core voltage.
The onboard RTC can provide very flexible Timing and Alarm Signals, the Atmel external Interrupts INT0 and INT1 are connected to the RTC to make use of this feature.
Once the counter value is measured, it can be stored in the dataflash memory or transmitted to a PC or whatever (ask for firmware).
The connection to the outside world is done by using a standard USB-UART Converter (FT232RL works great).
The power consumption of this circuit is very low when using the Power reduction modes of the Atmel controller. Depending on your program, it can be as low as several 10 microamperes. So this circuit is ideally suited for standalone long term measuring of radiactivity. Other sensors can be easily connected by using the I2C protocol, so this board is also a very good starting point for your own Ideas.
PCB Layout, PCB's available on request.
Data logger with battery Pack
Additional Information,Basics,DIY Kit, Links for Schematic