|source code (github)|
it was designed using through hole components, on a single layer PCB board. It features the Atmel 328p microcontroller, as the central processing unit, that runs the firmware code. There's a slot to mount a SBM-20 Geiger tube, a connector for the Ethernet module and one for the Nokia 5110 LCD screen. Both the LCD and the Ethernet adapter can be removed, allowing you to configure the final device: make that a portable dosimeter, a monitoring station or both. A speaker provides audible signals, including clicks and alarm, and a push button permits user interaction with the software. The bottom part of the PCB can be used to mount a battery holder for two alkaline batteries in series, or the unit can be powered using the DC connector, via a LM317 regulator. The entire board runs on 3V, and the high voltage inverter boosts that up to 380V (configurable in software up to 500V). The inverter uses a ferrite core transformer, connected to a switching transistor controlled via PWM signal by the microcontroller. An ADC port reads the high voltage level via a resistive divider, and adjusts the duty cycle so that the output voltage matches the value configured in the software. Therefore this is an efficient regulated high voltage supply.
PocketMagic DIY Dosimeter Geiger Counter