Saturday, August 16, 2014

Third Edition of Arduino Compatible DIY Geiger Kit released

It's time to introduce new third edition of our Arduino Compatible DIY Geiger Kit. As previous second edition, it still works as radiation detector board, but has several significant improvements and also new functions.
New electrical circuit design allows extremely low power consumption and also improves HV stability under fast count. 

Benefits of original third edition:
  • Kit consumes less than 0.06mA at background, usually 0.035mA
  • Improved HV stability up to 1000uSv/h radiation load
  • More supported tubes, 400V and 500V range select
  • Tube over voltage protection, limiting HV spikes
  • Wide compatibility with different MCU for software developers
  • TRRS socket for direct connection to Apple devices for “Geiger Bot”
  • Only DIP components to solder, SMD already installed
  • Simple assembling, no need to read electrical circuit

High Voltage Test Results:
Here is the data for HV tests with Philips 18504 Geiger tube. Technical specifications of the tube:

Initializing Voltage: 275V-325V
Beginning of Plateau: 425V
Ending of Plateau: 650V

The kit was set for 500V configuration. High voltage was measured on the point after 1N4937 diodes multiplier before 4.7M load resistor. We used 10Giga Ohm divider to get much more realistic results for high voltage measuring.
18504 tube has mica window that allows to demonstrate very intensive radiation load count when Am-241 sample placed closely to mica. The distance between mica surface and Am-241 was less than 1.00mm. High speed count under this condition is identical to 1200uSv/h Gamma radiation load, or at least it simulates extremely high load count conditions.
Another sample for test was piece of Fiesta Ware that usually on other counters measured as 10000 CPM or 60uSv/h load.
Current drawn
HV measuring
Background Radiation 0.1uSv/h
Fiesta Ware 60uSv/h
Am-241 simulating 1.2mSv/h

The test results shows very good parameters of HV converter. On background radiation kit can operate during a year period with just one battery set, in case you use 4x Ni-MH 1800mAh or greater. Under heavy load the current drawn is increased, but HV voltage stays in tube plateau limits that helping to keep GM tube parameters in recommended limits. 

You have an option to power the kit with one or two AAA batteries, but you need to add step-up module to the board. Of course when using 5V step-up module, the current consumption will grow. You can find more technical details in user manual PDF. 

Now the board support direct connection to iPhone or iPad if you need to use Geiger Bot application.
And as before for developers, the kit can be used with your favorite microcontroller through 3 wires connecting VDD, GND, INT. Interrupts connection is configurable, you can use resistor or bypass capacitor by activating internal pull-up resistor inside your software.

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