Radio watchman. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

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The described design is a security device that generates an alarm signal received over the radio channel in case of fire, when entering a protected room, etc.

As a receiving device, you can use portable radio stations such as "Meshchera", "Ural", as well as car radio stations in the CB range. The range, depending on the antennas used, can reach 3 ... 5 km.

(click to enlarge)

The figure shows a diagram of the device. Two generators are assembled on the D1 chip. The generator on D1.1, D1.2 is tuned to a frequency of 1 Hz and controls the operation of the second generator on D1.3, D1.4 with a frequency of 1 kHz.

Rectangular pulses through the UPT on VT1 and the key stage VT2 control the operation of the transmitter.

The transmitter master oscillator is assembled on a VT3 transistor with quartz frequency stabilization. Quartz is selected depending on the frequency of the receiving radio station. For example, the radio station "Ural" has a channel of 27,150 MHz. To work on the 3rd harmonic, you need quartz at 9,05 MHz. The power amplifier is made on a high-frequency transistor VT4 (KT904). Communication with the master oscillator is inductive, through L1, L2.

Coordination of the amplifier with the antenna - through the P-loop. As an antenna, you can use a stranded wire 1 ... 1,5 m long or a telescopic antenna from a radio receiver. The device is powered by a stabilizer with a voltage of 10..12 V, current - up to 1 A.

As a sensor, you can use push-button switches, reed switches, or simply contact plates mounted on doors and windows.

The security loop is a PEV-2 wire with a diameter of 0,3...0,5 mm, stretched along the perimeter of the protected premises.

In standby mode, point 4 is connected through a loop to a common wire (point 5). Transistor VT6 is locked. Relay K1 is de-energized.

When the loop breaks, the transistor opens and the relay is activated, becoming self-locking and supplying 12 V power to the alarm unit through contacts K1.2. The transmitter starts emitting pulses at a frequency of 27,15 MHz, modulated at a frequency of 1 kHz.

When an object is armed, for example, using a reed switch, indoors, inside a car, the power is turned on with the S2 "On" button. When the door closes, the magnet installed on the door closes contacts 1-3 of the reed switch. In this case, the capacitor is charged through the resistor to the voltage of the power source. In case of unauthorized opening of the door, the magnet leaves the reed switch, and contacts 1-2 are closed. The capacitor is discharged onto the winding of relay K1, the relay is activated, becoming self-locking through contacts K1.1, and contacts K1.2 supplies power to the transmitter.

Details. When developing the scheme, the goal was to use non-deficient parts. In the case of installing a radio watchman in a car, you can use the K1 relay of the RES-22 type, passport 129, as well as any relay with an operating voltage of 10-12 V. A jumper is placed between points A and B. In this case, the network unit is not needed. In the network version, the RES-relay 22, passport 163.

For D1, a replacement is possible - K176LE5, K561LA7; VT4 - KT610, KT911, KT913, KT606 Reed switch - KEM-3 type. Network transformer - any, with an output voltage of 12. .24 V.

Inductor data for the 27 MHz band:

• L1 - 12 turns with PEV-2 wire with a diameter of 0,3 ... 0,5 mm;
• L2 - 3. 5 turns next to L1;
• L3 - 9 turns with PEV-2 wire with a diameter of 0,5 1,0 mm;
• L4 - 20 turns with PEV-2 wire with a diameter of 0,5 mm.

Coil frames - from UPCHI TV nodes with a diameter of 7,5 mm.

Resistors - MLT-0,125. Ceramic capacitors - KM5, electrolytic capacitors - K50-6.

The establishment of transmitters is described in the literature and is not given here.

This design has been tested and has been working flawlessly for several years.

Author: V.Panov, Kaluga; Publication: N. Bolshakov, rf.atnn.ru

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