Currently, electronics is one of the most dynamically developing branches of science and technology. Its technologies are present in almost every area of human activity.

A Geiger-Muller counter is a device consisting of two electrodes placed in a gaseous medium at low pressure - a cathode with a large area and an anode in the form of a more or less thin wire, which creates a local high-intensity field in which the ion multiplication process develops. account of which a single ion pair can cause a powerful ionization avalanche and self-discharge ignition.

The principle of operation of the Geiger counter is simple. A thin-walled tube with a low pressure gas inside (Geiger-Müller tube) is exposed to a high voltage current. The generated electric field is insufficient for dielectric breakdown, so no current flows through the tube until a photon of ionizing radiation passes through it.

When beta or gamma radiation passes through the tube, it can ionize some of the gas molecules inside, resulting in free electrons and positive ions. The particles begin to move under the influence of an electric field, and the electrons pick up enough speed to ionize other molecules, which leads to a cascade of charged particles that conduct current for a short time. This short current pulse can be recorded using the above circuit, which creates a clicking sound, or, as in this case, sends information to an external microcontroller INT, which can perform calculations with this data.

The Geiger counter requires a high voltage power supply to operate.

The power is supplied to the meter through a ballast resistance of several megohms - it limits the current impulse and reduces the voltage on the meter after the impulse has passed, making it easier to extinguish. The value of this resistance is given in the reference data for a specific device - its too small value shortens the life of the detector, and too large - increases the dead time.

The DA1 microcircuit generates square-wave pulses of about 14KHz. Due to the fact that the transistor VT2 opens and closes, current jumps with a voltage of about 200V occur at the constant choke L2.

Pulse diodes VD1, VD2, VD3 and high-voltage capacitors C6, C7 form a voltage multiplier. After the multiplier, we get a voltage of 350-450V on the tube. Fine adjustment occurs with the multi-turn potentiometer R9 due to the feedback on VT1. As soon as the current becomes too large, VT1 closes the DA1 timer, thereby reducing the voltage.

The voltage at the output of the multiplier changes slightly when the batteries are discharged, its values ??remain within the tube plateau.

R12 is the tube terminating resistor and is set according to the tube documentation (5-15 mega ohms).

Registration and amplification of pulses is performed on an NPN transistor VT3. The transistor operates in the electronic key mode - every time a pulse comes from the tube, it opens, thereby changing the logic level on its collector. This state change is a trigger for DA2 and DA3. A single vibrator is assembled on the DA2 microcircuit. Its task is to stretch too short a pulse of 50 μs to flash the diode and turn on the piezo emitter.

The DA3 microcircuit performs the function of a repeater. It amplifies the current and does not allow external noise to flow into the signal line.

The main parameters of the electronic device:

Supply voltage - 4.5-5V

Supported counters - M4011, STS-5, SBM20, J305, etc. (operating voltage 330-600V)

Interfaces - SPI, AUX

Board dimensions - 93 x 108 x 20mm

Indication - signal line, buzzer, LED