The automatic switch of radio equipment with protection against unauthorized inclusion. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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The automatic switch of radio equipment with protection against unauthorized inclusion. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches

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In amateur radio literature, various designs of circuit breakers have been repeatedly covered. Many of them have significant drawbacks, for example, to connect to the device, you need to remove the cover, breaking the seal, the ability to turn off the load only at the end of the transmission.

I propose another version of the switch (Fig. 1). This design can be made at will both in the form of a separate unit, and mounted directly on a TV, radio, tape recorder, etc.

(click to enlarge)

You can power the auto switch from any low-power transformer with a secondary voltage of 6-9 V (not shown in the diagram). The time the load was in the on state was chosen arbitrarily, and with these ratings, the time of the driving circuit of the C1R1 generator, as well as when switching the outputs of the counters made on the DD3 and DD4 microcircuits, is approximately 90 minutes (the average time of a feature film).

If during this time the sensor plate is not touched again, the load will automatically disconnect from the network. Of course, the time the load is in the on state can be easily changed in one direction or another by selecting the R1C1 circuit, changing the switching of the outputs in the DD3 and DD4 microcircuits, as well as introducing additional counters and switches. The auto switch consists of a time relay, which contains a master oscillator on the elements DD1.1-DD1.3, a frequency divider DD3, DD4, a trigger on DD2, a sensor device on transistors VT2-VT4 and relay K1, and an actuator on VT1, relay K2, thyristors VS1, VS2, stabilizer on VT5.

To start the circuit breaker, it is necessary to connect it and the load to the network. When the power is turned on, the pulse from the output of the C2R2 chain will set the trigger DD2 to zero, the relay K2 will de-energize. At the inverse output 2 of the trigger DD2, a log "1" will be set, which will disable the operation of the master oscillator, relay K1 will de-energize, the load will be disconnected from the network. To turn on the TV, you need to touch the sensor plate with your hand, while relay K1 will work and its contact K1.1 will close.

At the output of the trigger "S" DD2 (pin 6) a short pulse will appear, which will set it to the state of the log. "1". At the output 1 of the trigger DD2, a log "1" will be set, the relay K2 will work, which, with its contact K2.1, will close the control circuit of the thyristors VS1 and VS2, the load "R.N." connect to the network. Since the log "2" is set at the inverse output 2 of DD0, then simultaneously with turning on the load, the prohibition from the master oscillator (MG) is removed, and the counting of pulses by the counter on DD3 and DD4 begins. After the time has elapsed (~ 90 min), if you do not touch the sensor plate again with your hand, the decline in the positive output pulse of the counter, inverted in element DD1.4, will switch trigger DD2 to the zero state, while the master oscillator will be disabled, relay K2 will turn off, the load is disconnected from the network.

To restart the load, touch the sensor plate. In order not to disconnect the load (in this case, the TV), you need to touch the sensor plate again at least once (before 90 minutes have elapsed). After touching the touch plate again, the TV will stay on for 90 minutes.

If the touch plate is installed in a certain place known only to the owner, then only you can turn on your TV (radio, tape recorder, etc.). The touch plate (sensor) can be any metal part of the apparatus lining, screw, pin, handle, etc., not connected to the body. If the length of the wire connecting the sensor and the circuit is more than 30-50 cm, it must be shielded, since false alarms are possible due to pickups.

A correctly assembled circuit from serviceable parts does not need adjustment and starts working immediately. You may have to pick up capacitor C2. Selection is necessary only if, after the initial connection to the network, spontaneous connection of the load occurs without first touching the sensor plate. To connect a more powerful load, the type of thyristors must be changed to KU202N, and also installed on radiators.

Chips can be replaced with similar K176, K564 series. Transistors KT361, KT315 with any letter index. Relays K1, K2 are any that reliably operate at voltages up to 7 V and possibly low current. The value of the fuse depends on the current consumption of the load. It should also be remembered that the unused inputs of the DD2 chip (8, 11, 10) must be connected to the case, and the input 9 of DD2 to the "+" bus. To avoid malfunctions, it is desirable to install the device closer to the DD2, DD3, DD4 microcircuit cases.

The printed circuit board (Fig. 2) is made of double-sided foil fiberglass with a thickness of 1,5 mm.

Automatic switch of radio equipment with protection against unauthorized inclusion

Details VD3, VD2, R6, VS1, VS2 are installed outside the board. Blocking capacitors type KM 0,068 uF.

References:

Biryukov S. Time relay for amateur photographer // Radio.-1988.-№12.-S.53-55.
Borovsky V.P. and others. Handbook of circuitry for radio amateurs.-K .: Tekhnika, 1987.

Author: V.G. Braichenko

See other articles Section Clocks, timers, relays, load switches.

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