Vermes
Advanced Member level 4
The counter is made in BOB303 tube.
Principle:
The tube is filled with a mixture of gases. Constant voltage is set to its outputs – about 340V. The power is from an inverter build on a NE555, IRF840 transistor and a 230/6V transformer.
When beta or gamma particle passes through the tube, the gas ionizes – a small discharge occurs in a fraction of a second current flows through the tube. Impulse arises, which is headed by a monostable transistor to the generator, which is connected to a buzzer and a pulse counting microcontroller.
The microcontroller is AT89C2051, the program is written in C. For now, the device only signalizes if there is a radiation; in the future, there will be also an information on a LCD screen about the dose.
Link to video:
Information about the tube:
type: BOB-33
filling: Ne + Ar + chlorine extinguishing agent
threshold voltage (hi): 300V
work voltage: hi+40V
length of the plateau: 80V
slope of the plateau: 0.125%/V
deadtime: 150us
durability: 10^10 impulses
use: measurement of beta radiation medium energy and gamma. For portable devices
construction: glass tube
Link to original thread – Licznik Geigera, detektor promieniowania beta i gamma