Digital dosimeter GAMMA_1. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Digital dosimeter GAMMA_1. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Dosimeters

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Digital dosimeter "Gamma_1" is designed to determine the level of ionizing radiation. Responds to beta, gamma, and X-rays. The measurement is made for a time of 1 min in units of μR/h, also units exceeding the natural background radiation (NRF) ~=15-25 μR/h.

The device has on board

1) English-Russian display 2x16 characters with backlight.
2) 3 measurement modes single/cycle/sleep with low power consumption.
3) 2 cells of non-volatile memory for recording measurement values.
4) Buffer value of the previous measurement.
5) Adjustable alarm level with memory.
6) Light/sound visualization of radiation.

(click to enlarge)

Switching modes is done with the buttons "<" ">" (SB2 / SB3) Turning on / off the modes "V" "X" (SB1 / SB4) Initially, the single measurement mode is selected, press SB1, measurements are taken in a time of 1 min, after which the result is buffered for further recording of the value and viewing the previous measurement. To enable the continuous measurement mode, you must go to the menu "mode 1-test / 2-cycle" (Fig. 3) press "X"-mode 2, "V"-mode 1. To save the result, select the menu "Zone1 or zone2" press "V " Write from the buffer, press "X" to read from the cell.

To turn on the backlight, select the menu "Backlight on / off" - "X" - off, "V" - on. The alarm level is adjusted in the "Alarm/Level" menu, using the "X"--1, "V"-+1 buttons we change the level and save it to memory.

The level changes in units of NRF. If the selected level coincides with the measured level, an alarm sounds and the screen displays "attention high radiation level!".

In sleep mode, it is performed with reduced power consumption, the blocking generator operates in a pulsed mode, the backlight turns off on the screen every 10 seconds "scanning" is displayed, in this mode no values \u1b\u1bare recorded, it only reacts to an excess of radiation levels with a sound signal. The HL2 LED and the HA1 resonator indicate that a radioactive particle has hit the sensor, HL2 indicates that the battery is being charged. Using a single vibrator assembled on DD1, we convert the pulses from the sensor into an impulse of the required time and amplitude for the DD1 controller. Jumper JXNUMX (not set by default), turns on the second sensor and serves to increase the sensitivity of the device, but at the same time, adjustments should be made. Jumper JXNUMX (by default) turns on the acoustic emitter.

Digital dosimeter GAMMA_1

Replacing parts

Chips in Dip package, DD1-K561la7, K176la7, K1564la7, DA1-roll5, 78L05.
Transistors VT3,4 kt315, kt3107 and other low-power NPN.
Transistor VT2 kt361, and other low-power PNP.
The Geiger counter SBm20 is available in three versions and will be replaced by the STS-5, only the dimensions change.
Any LEDs for a current of 5-20mA.
Tact buttons are standard 5x7mm.
Acoustic emitter of piezoelectric type, can be ZP-19,
ZP-5, ZP-3, IMPORTED (HPE-227).
Sound generator from the HCMxxxx series, for voltage from 1-3V.

For surface mounting

Chips, DD1-CD4011B, DA1-L78m05cdt-tr, DD2-Atmega8 UA tqfp32,
Transistors VT3,4 BC847 and other low power NPN.
Transistor VT2 BC857 and other low power PNP.
Variable resistor R10 type PVZ3A-103

Digital dosimeter GAMMA_1

The blocking generator transformer is made on a ring made of ferrite with a permeability of 2500-4000, with a standard size from K16x10x4,5 mm to K20x12x6mm or an imported already rounded and varnished ring of the type B64290-L743-X83 16x9x5.

Windings 1-200** turns with PEV wire 0.07mm
2 - 8 turns with PEV wire or better with silk insulation 0.1-0.3mm
3-3 turns with the same wire.
Figure 6 shows how to properly wind and mount the transformer.

Digital dosimeter GAMMA_1. Interface

Design

We mount the digital part of the circuit on the board together with the buttons, the LCD module and the sound generator.

We make the high-voltage part of the circuit (Fig. 2) on another board, on it there is a blocking generator, a multiplier, and a detector chamber consisting of one or more Geiger counters, under them we cut out a rectangular window on the board.

In order not to significantly weaken the received radiation, we carefully cut a window in the lower part of the housing cover exactly under the detector chamber, which should be covered with thin plastic (for example, from a floppy disk) with often drilled holes.

The device is powered by a voltage of 6-9V, a krone battery or 2 series-connected batteries from a mobile phone with an internal charge controller remote in is used, if batteries are used, then the charge circuit should be excluded. Buttons can be taken from the old Tetris.

Setting

We adjust the contrast of the display with a resistor R10, R11 is the brightness of the backlight to the best result.

The most pliable section of the blocking oscillator circuit, for starters, we connect the output of the resistor R2, right according to the circuit, to the circuit section + 5v (kt1). Then we connect the oscilloscope to the VT1 collector, generation should be observed, if there is no generation, the ends of winding 3 should be swapped.

To write a program to the controller, you must

Write gamma_1.eep to EEPROM.

Write gamma_1.hex to FLASH memory.

The microcontroller is configured to operate an internal generator, the fuse setting is shown in Figure 5.

Digital dosimeter GAMMA_1. Fuzz setting

If you need to change the program, you must first completely erase the memory from the EEPROM and FLASH crystal in order to avoid errors.

Digital dosimeter GAMMA_1. How to wind a transformer

Digital dosimeter GAMMA_1. Detection chamber

Download source code and firmware (100 kB)

Author: Knyazev I.S. (Knazev33), Knazevis_ [dog] mail.ru, ICQ: 455864760; Publication: cxem.net

See other articles Section Dosimeters.

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