Economical power supply for the Geiger counter. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Dosimeters
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In autonomous devices for continuous radiation monitoring using Geiger counters as radiation sensors, the main energy consumer is a device that converts the low voltage of the device's power source into a voltage of 360 ... 440 V, corresponding to the plateau of the counting characteristic of the halogen Geiger counter (see Appendix 4). A schematic diagram of an energy-efficient voltage converter is shown in fig. 80.
Rice. 80. Economical Geiger counter power supply (click to enlarge)
It is based on a blocking generator, on the output winding of which short (5 ... 10 μs) pulses with an amplitude of about 420 V are formed. Through the diodes VD3, VD4 they charge the capacitor C4. This capacitor will be the power source of the Geiger counter (recall that the conductivity of the Geiger counter in the pause between excitations is close to zero).
The energy efficiency of the converter is ensured by the fact that the interpulse pause in its blocking generator is set not by its own timing chain R1C3, as is usually done, but by a single vibrator (DD1.1, DD1.2, etc.) operating on microcurrents [2]. The duration of the pause in it tp@R3·C5 is chosen so that the voltage at the output of the converter in the background counting mode is close to the highest voltage value at the plateau of the counting characteristic of the Geiger counter. (In the future, the decrease in voltage at the output of the converter, its shift to the other edge of the plateau will be due only to a decrease in the voltage of the power source.)
The blocking oscillator will generate an extraordinary impulse to recharge the capacitor C4 if a provocative impulse occurs at the input 2 of the DD1.2 element. If this pulse occurs every time the Geiger counter is triggered, then this will keep the voltage at the output of the converter at a level that does not depend on the count rate.
The transformer T1 of the blocking generator is wound on a ferrite core made up of two rings M3000MN 12x8x3 mm. The rings are glued together, their sharp edges are smoothed with sandpaper, and the entire core is wrapped with a thin fluoroplastic or lavsan tape.
First winding II is wound, it contains 420 turns of wire PEV-2 0,07. The winding is carried out in one direction, almost turn to turn, leaving a "gap" of 1 ... 1.5 mm between its beginning and end. Winding II is also covered with a layer of insulation. Next, winding I is wound - 5 turns of wire PEVSHO 0,15 ... 0,2 - and along it - winding III - 2 turns of the same wire. These windings should be distributed as evenly as possible over the core.
The correct phasing of the transformer windings (the dots show their common-mode ends) must be observed during its installation. You should not experiment with this - you can burn the transistor.
In the converter: resistors Rl, R2 - type MLT-0,125, R3 - KIM-0,125; capacitor C1 - any oxide, C2, C5 - type KM-6 or K10-176, C3 - K53-30, C4 - K73-9.
Converters of such a structure essentially cover the very problem of supplying Geiger counters from low-voltage sources: the current consumed by such a converter is already a small part of the self-discharge current of most galvanic batteries.
Publication: cxem.net
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