Automatic lighting switch. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches
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The automatic lighting switch allows you to turn off the lighting 3 minutes after the switch button and turn on the light for the same time when a loud sound signal is given (clap, call, voice, etc.).
The machine is connected in parallel with the contacts S1 of the light switch. The supply voltage is supplied to the machine when the contacts S1 are disconnected. In this case, the capacitor C3 is charged through the resistor R7, the diode V4 and the control electrode circuit of the thyristor V5, as a result of which the thyristor V5 opens and closes the diagonal of the rectifier bridge V6-V9. The lamp will remain on. As the capacitor C3 charges, the control current of the thyristor V5 decreases and after 3 minutes the thyristor will close. As a result, the diagonal of the bridge V6-V9 opens and the lamp H1 goes out.
When exposed to sound vibrations, a series of pulses appear at the output of microphone B1, which, through the capacitance C2, act on the thyristor V3 and open it. Capacitor C3 is discharged through resistor R10 for about 4 s and keeps thyristor V3 open. Due to this, through the resistor R7, the diode V2, the thyristor V3, a pulsating current is supplied to the control electrode of the thyristor V5. The thyristor V5 opens, the diagonal of the bridge V6-V9 is shorted and the lamp H1 starts to burn until the capacitor C3 is discharged. Resistor R3 regulates the sensitivity of the machine to sound signals.
Details. Diodes V6-V9 type D226 KhPRI switching loads up to 100 W) or D246 (when switching loads up to 1 kW); any carbon microphone, for example, capsule MK-59 or MK-10; capacitor C3 type K50-7; zener diode V1 types D808-D813, D814A-D814D.
The establishment of the machine is reduced to the selection of the resistor R8. With a decrease in resistance R8, the sensitivity of the thyristor V5 and the time delay of the machine increase.
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