Acoustic relay for lamp. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting

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Incandescent lamps in terms of electricity consumption occupy one of the first places among other household appliances. Even in a small apartment, more than a dozen light bulbs are usually used. In order to reduce energy consumption, an automation device is needed.

The relay option described below is designed to work with incandescent lamps with a total power of up to 1000 watts. It is distinguished by simplicity, high reliability of the design, availability of the element base, easy repeatability and a minimum of adjustment. The device smoothly lights the lamps at full power for 0,5...2 s and slowly extinguishes them after the end of the exposure time for 15...20 s with a delay in the rate of decrease in the brightness of the glow at the very end of the process by 2...6 s. The acoustic relay has a high sensitivity, the level of which is easily adjustable, it is resistant to both impulse mains interference and short sound ones. After power-up, at least 97% of the power is supplied to the load.

The relay turns on the lighting if the level of acoustic noise exceeds the set value, and smoothly turns off the power to the load after a set time, if there is silence. The device, as it were, "reasons": if it is quiet, then there is no one in the room, and the lamps can be turned off after a while.

Let's turn to the device diagram (see figure).

(click to enlarge)

When the switch SA1 is closed, the mains voltage of 220 V is applied to the device, and the incandescent lamp EL1 quickly, but still smoothly lights up, regardless of whether there was sufficient acoustic impact from the BM1 microphone or not. The logic is simple: if you flip the switch, you need light. If the silence is not broken, the EL1 lamp will go out after 40...60 s.

A small-sized imported electret microphone is used as an acoustic sensor. The microphone amplifier is built on the half of the operational amplifier (op-amp) DA1, which is powered by a unipolar voltage. To do this, approximately half of the supply voltage, formed by a divider from R1, R2 and a microphone, is applied to its non-inverting input. This inclusion saves a few details. The sensitivity of the microphone amplifier is determined by the ratio of the resistances of the resistors R3 and R4. An amplified sound signal is detected on diodes VD1 and VD2. As soon as the voltage on the capacitor C6 exceeds the voltage on the capacitor C7, the comparator DA2.1 will switch, the voltage log "6" will appear at pin 1. Since the capacitor C6 charges relatively slowly, the lamp EL1 lights up at full power with a delay, which reduces the likelihood of it burning out at the moment of switching on. The 574 series op amps have FETs at their inputs, and their input impedance is very high. Therefore, to obtain a long time delay, a time-setting capacitor C6 of small capacity is sufficient.

When a log "1.2" appears at the output of DA1, a relaxation generator is turned on on a unijunction transistor VT1, the load of which is a pulse transformer T1. Since the second base circuit is powered by a pulsating voltage, the operation of the generator is synchronized with the mains frequency. This makes it possible to easily phase control the power supplied to the load. When the voltage on the capacitor C6 drops to 2 V, the voltage at the output DA1.2 also decreases. The pulses that open the triac are fed to its control output at each half-wave of the mains voltage with an ever-increasing phase delay, the EL1 lamp goes out smoothly. With the ratings R5, C6 indicated in the diagram, when silence sets in, the lamp operation time at full power is about 3 minutes, and the extinction period lasts about 20 s.

Low-current triac control units are powered by a simple parametric stabilizer, consisting of capacitor C10, resistor R11, rectifier bridge VD5, diode VD4, zener diode VD3 and capacitor C8 smoothing the rectified voltage. Capacitor C11 reduces interference penetrating into the network, the level of which increases for a short time before the lamp goes out.

Details. The device can use resistors C2-22, C2-23, MLT, BC and other appropriate power. The high-resistance resistor R5 can be made up of several resistors. Capacitors: C1 - types K10-17, KM-5, KM-6; C4, C9 - types K73-9, K73-17; C10, C11 - K73-16, K73-17 for a voltage of at least 400 V.

Capacitor C6 can be taken from the K53 series with possibly lower leakage currents, and can also be made up of several film capacitors. The remaining capacitors are types K50-35, K50-24 or imported analogues. Transistor VT1 can be taken from any of the KT117 series. KR1UD574A, KR2UD574B work steadily as DA2. You can also use op-amps of the K574UD2 (A-B) type, but they have a different pinout. The triac can be replaced by KU208D1, TS112-10-4, TS112-16-6 or another similar one for a voltage of at least 400 V and a current corresponding to the load. The diode bridge can be replaced by KTs422G, DB104, DB107 or 4 diodes, for example, KD243Zh, KD105B, 1N4007. Diodes 1N4148 can be replaced by any of the series KD103, KD521, KD522. Any low-power 12 ... 14 V zener diode is suitable, for example, D814D, KS512A, KS213Zh. The microphone can be used in the MKE-337-1, MKE-378 (A, B), MKE-389-1, MKE-332, MKE-333 series.

The transformer is wound on a K10Ch6Ch3 ring made of M2000NN ferrite. Before winding, the sharp edges are ground down, the ring is covered with a thin layer of epoxy resin or several layers of zaponlak.

Both windings are wound with PESHO, PELSHO wire with a copper core diameter of 0,08 ... 0,1 mm. The primary winding contains 130 turns, the secondary - 70. After winding, the primary winding is impregnated with zaponlak. You can also use quick-drying nail polish or BT-577 varnish. You can take the ring K12Ch8Ch3 or a ferrite cylinder from the IF coils of the Alpinist receiver.

Adjustment. By selecting resistor R1, you need to set the voltage to +6 V at pin 2 of DA1.1, by resistor R7 - voltage of +2 V at pin 5 of DA1.2, by adjusting the tuning resistor R3, set the desired acoustic sensitivity of the microphone amplifier. Instead of resistor R9, a 22 kOhm trimmer is temporarily connected. Slowly reducing its resistance, the brightest glow of the EL1 lamp is achieved. After that, the resistance of its introduced part is measured and, instead of the trimmer, a constant is set to the same resistance.

If the lamp does not light up at full power, then you need to change the conclusions of one of the windings of the pulse transformer.

A triac in a plastic case TO220 is installed on a heat sink with a load power of more than 40 watts. The maximum power of a controlled lamp or several incandescent lamps connected in parallel depends on the type of heat sink used. In the author's version, the device is mounted on two boards with dimensions of 65x32 mm and is intended for installation in a decorative protective glass of a pendant lamp with one lamp with a power of 100 W. If you install a diode in parallel with the SA1 switch, for example, KD226E, then the incandescent lamp will remain on until SA1 closes, but if you then try to turn it off by opening the same contact, you will see something interesting, but for this you need to first assemble what is described in this article device.

Since the design has a galvanic connection with the mains voltage ~ 220 V, the safety rules must be observed when setting up and operating the acoustic relay.

References:

1. Butov A.L. Acoustic light switch//Radio. - 2001. - N12. - C.30.

Author: A.L. Butov

See other articles Section Lighting.

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