Sound relay. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches
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In the sound relay, the diagram of which is shown in the figure, a small-sized loudspeaker from a pocket radio receiver is used as a sensor. The resistance of its voice coil should be of the order of 30-60 ohms. To better match the resistance of the sensor with the input of the device, the first stage is made according to the scheme with a common base. The second and third stages are assembled on transistors with different types of conductivity (npn and pnp).
The device works as follows. The sound signal received at the input of the device is amplified by all three stages and, acting as a switching signal, is fed to the control electrode of the thyristor D1. An actuator is connected to its anode circuit through the output sockets. For example, a flash, an electromagnetic relay that turns on the camera shutter, etc.
The sensitivity of the amplifier can be changed within certain limits by setting the variable resistor R7. The handle of this resistor is displayed on the front panel of the device.
To achieve greater clarity of relay operation in the first two stages, it is desirable to use silicon transistors with high gain and low leakage currents.
In the first two stages of the device, silicon transistors KT315G can be used, in the third stage - a silicon transistor MP 116. In this stage, it is also possible to use a germanium transistor, for example, MP25 or MP26 with any letter. The electromagnetic capsule DEM-4 can be used as a sensor.
Literature
- "Practical Wireless", 1972, January.
Publication: N. Bolshakov, rf.atnn.ru
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