Acoustic relay. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Acoustic relay. 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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I present to your attention an acoustic relay. This circuit is quite simple even for beginners, it has only one microcircuit, one transistor, several capacitors, resistors and two relays.

It all started with the fact that I have a lamp hanging on the wall in my country house, and when I go up to my 2nd floor late in the evening, it is difficult to turn on this lamp in the dark until you reach it :-). Based on this, the idea came to my mind to assemble such a thing that would turn on the light with a clap, and turn it off at the second clap.

I did not come up with this scheme myself, but simply joined two designs into one. It turned out pretty compact! And I decided to shove my creation right into the lamp, or rather, where the electronics of this lamp used to be. There was a lamp brightness control, and now an acoustic relay. Who did not understand what kind of lamp this is, see the picture:

acoustic relay

Relay working principle

Let's start from the moment when a beep sounded in the microphone. The microphone, being the sensor of the device, converted the sound of a clap into an el. a signal that enters through the capacitor C1 to the input of the K157UL1A microcircuit, which is a preamplifier. Further, the amplified signal from the microcircuit is fed through the capacitor C6 to the cascade assembled on the transistor VT1. It is both an AC voltage amplifier and a DC amplifier. From the collector of the transistor VT1, the signal goes to the relay K1, which turns on, but not for long, it depends on the duration of the sound signal. This time is enough for the contacts of relay K1 to close and send a signal to the trigger made on relay K2. When the trigger turns on, relay K2 is activated, which turns on the load with some contacts, and controls the trigger with others. The correct operation of the trigger is achieved by selecting the resistance of resistors R8 and R9.

(click to enlarge)

Acoustic relay setting

At the first clap, the lamp should light up, and at the second clap, it should go out. If it lights up with a pop, and immediately goes out after it, then the current flowing through the resistor R9 and the winding of the relay K2 is lower than the release current. In this case, you need to twist the variable resistor R9. This can also be observed: the lamp turns on, but does not turn off. This indicates that the current flowing through the resistor R8 and the relay winding K2 is higher than the release current, and it holds the relay armature. So you need to twist the resistor R8.

Download file printed circuit board in LAY format

Authors: Tera (Dmitry), dmitryter89 [dog] yandex.ru, Sergey Ilyushkin; Publication: cxem.net

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

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