First, I will explain the basics of how everything works. The Geiger counter uses a special tube filled with an inert gas at very low pressure to detect radiation. Inside this tube there is a cylindrical piece of metal that acts as a cathode. Inside this cylinder there is a small metal piece of wire that acts as an anode. When a high voltage is present at the anode of the tube, nothing happens, but when ray particles enter the tube, it causes ionization of the inertial time, and it starts to conduct an electric current. This current can be measured with special devices, but in this scheme there will be only a detection signal of the presence of radiation.
Geier counter circuit
The Geiger counter consists of two parts: a high-voltage power supply - a converter and a detector.In the above scheme, the high-voltage circuit consists of a timer 555, on which a generator is built. The timer 555 generates rectangular pulses, which through the resistor opens and closes the transistor periodically. This transistor controls a small step-up transformer. From the output transformer, voltage is applied to a voltage doubler, where it rises to about 500 volts. Then, the voltage is stabilized by using zener diodes up to 400 volts, necessary to power the tube of a Geiger counter. The detector consists of a piezo-electric element connected directly to the anoud tube without any amplifiers.
Tools and Parts
To complete this project, you need various tools and materials. Tools:
Stripper for stripping wires.
Gun withhot glue.
Details:most of them can be found from old electronic devices.
Transformer 8: 800 - it was a transformer power source of a broken alarm clock.
The tube of the Geiger is purchased -HERE.
Resistors 47K (x2).
Capacitor 2.2 nF.
Any N-channel MOSFET.
1n4007 diode (x2).
100 nf capacitor at 500 volts.
Zener diodes - 100 volts (x4)
Piezoelectric element (from an old microwave oven).
Generator Assembly with MOSFET Transistor
Once you have gathered your tools and materials, it's time to go to the component soldering. The first thing you need to solder is a generator and a transistor. To do this, install each component on the breadboard board in the most efficient way. For example, solder MOSFET near where with a transformer.This will help you use less wires when soldering. As all the parts are smacked between each other, cut off the excess wire.
Solder the transformer and voltage doubler with stabilization
After assembling the generator, you need to solder the transformer winding with less resistance between the MOSFET power plus. Then solder the transformer output from the high-voltage winding to the doubler. Then, solder all capacitors and zener diodes. After soldering a high-voltage power supply, you need to check it with a voltmeter to see that it is assembled correctly and gives the correct voltage. If you have another Geiger tube, not like mine, look at its specifications to find out its supply voltage, which may be different. Then add the appropriate zener diodes.
Adding a Geiger tube and detector
The final part and it remains for me to add the tube itself — the counter and the detector. Begin to solder the wires to each end of the tube. Then, we solder the anode to the output of the regulated power supply and the cathode to the piezoelectric element. Finally, solder the piezoelectric element to the common wire. The noblest use of a detector consisting of only two components is the simplest Geiger counter. Most of the more complex counters contain transistors in the detector. No current limiting resistors are needed in this detector because of very small currents.
Finally, it is time to check the Geiger counter! To do this, first connect the meter to the power supply.Then, take the radioactive source for verification. Using pliers, hold the radiation source near the Geiger tube. You should hear a few noticeable clicks that are heard in the piezoelectric element. This means that the counter is working properly. To hear and see this, watch the video. Thank you for reading!