Autonomous signaling device of mains voltage disconnection. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Indicators, sensors, detectors

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Some household electronic automatic installations require a constant supply of 220 V AC, such as incubators, cold stores, security systems, and many software-controlled devices. Therefore, unpredictable power outages are highly undesirable, especially at night, when they can go unnoticed. To reduce the likelihood of unjustified losses, I propose to make a simple device.

In less than one hour, you can assemble a simple transformerless 220 V AC outage alarm (Fig. 1), which contains a minimum of parts and does not require any adjustment. The device emits a loud intermittent sound signal 2...3 s after the power supply is turned off. The duration of the sound signal is at least 3 minutes.

The device contains only three active elements: a silicon epitaxial-planar field transistor with a pn-junction gate and an n-type channel, a blinking HL2 LED, and a piezoceramic sound emitter with a built-in BF1 generator. Nothing good comes for free, and simplicity requires some sacrifice. However, slightly increased costs for the purchase of a flashing LED and a tweeter pay off with a XNUMX% repeatability of the design.

The mains voltage is rectified by a half-wave rectifier on diodes VD1 and VD2. To improve the reliability of the XNUMX/XNUMX device, two rectifier diodes are installed.

Excess rectified voltage is quenched by resistors R1, R2. The parameters of these resistors are chosen so as to avoid damage and fire of the device in the event of an accident in the mains, when 220 V or more is supplied instead of 380 V, which often happens both in cities and in rural areas.

Through the signal LED for turning on the HL1 network, the resistor R3 and the zener diode VD3, high-capacity capacitors C3, C4 begin to charge. The maximum voltage to which they are charged is limited by the zener diodes VD5, VD6 at the level of 22 ... 24 V. The process of fully charging these capacitors takes about 8 minutes.

In the presence of a supply voltage of 220 V, the transistor VT1 is closed by a negative gate-source voltage (7 ... 9 V), which is obviously greater than the cutoff voltage of this field-effect transistor.

When the mains voltage is turned off, the capacitor C2 is quickly discharged through the resistor R3. This leads to the opening of the transistor. At zero gate-source voltage, this transistor operates as a source of a stable current, the value of which weakly depends on the drain-source voltage. When the transistor channel is opened, the chain of a flashing LED and an electronic buzzer is initially supplied with a voltage of 10 V, which is limited by the stabilization voltage of the protective zener diode VD4. The LED starts flashing at a frequency of about 2 Hz, in time with it B.1 emits a two-tone beep. Capacitors C2, C3 gradually release the accumulated energy, beeps continue until the voltage across these capacitors decreases to 2,2 ... 2,5 V.

For those who cannot purchase a blinking LED or want to build this device a little differently, Fig. 2 shows a circuit of a current interrupter that can be used to replace a blinking LED in this design. The breaker is included in the circuit in accordance with the specified polarity instead of HL2. In this version of the signaling device, the duration of the alarm signal is doubled.

Details. Resistors can be used types MLT, C2-23, C1-4 of the corresponding power. Oxide capacitors C3, C4, it is desirable to take modern imported small-sized ones with low leakage current (the author used Philips capacitors). Good results are also obtained with 4 domestic capacitors of the K50-24 type (2200 μFCh63 V).

Diodes VD1, VD2 can be taken types KD102B; KD209A-G; KD 221V, G; KD105V, G; 1N4004. Zener diode VD3 - any low-power 7 ... 9 V (KS175A, KS182Zh, KS191M). VD4 can be taken types KS210B, KS580A, D814B, KS512A. Two zener diodes connected in series VD5, VD6 can be replaced by one type KS520V, KS522A, KS524G, KS222Zh. It is desirable to take the HL1 LED with an increased brightness of the glow, since it operates at an average current of less than 1 mA. Many LEDs of the KIPD21, KIPD36, L-1513, L-1503, L-934 series are suitable. A blinking LED can be taken of any type that allows a supply voltage of 9 ... 12 V, for example L-36BSRD, L-816DCRD, L-796BGD [2]. The sound emitter is suitable for any type with a built-in generator with an operating voltage of 10 ... 15 V, consuming a current of not more than 6 mA at Upit = 10 V, for example HPA17AX.

You can use the table from [3]. The type of "tweeter" indicated in the diagram makes a very loud sound already at an operating current of more than 600 μA.

It is advisable to take a field effect transistor with an initial drain current of about 1 mA. The closest in this parameter are transistors of types 2P303A, KP303B, KP303Zh. Transistor type KT3102B can be replaced by KT3102A-V, I, K; KT315V-D; KT342A; SS9014; SS9013. Transistor type KT3107B - KT3107A, V, G, D, I, K; KT361G, D, K, P; KT501D-M; SS9015; SS9012.

When assembling and setting up the device, it should be remembered that it is galvanically connected to the ~220 V network. The luminous HL1 LED will inform you in time that the signaling device is not disabled. You can use the recommendations from [4].

To forcibly turn off the sound signal, a momentary button P2K, PKN can be provided, when pressed, capacitors C15, C1 are forcibly discharged through a resistor with a resistance of 2 ohms and a power of 3 W.

References:

1. Aleshin P. Voltage outage signaling device//Radio. - 2002. - No. 5. - P.52.
2. Ryumik S. All about flashing LEDs//Radiohobby. - 2002. - No. 1. - P.31.
3. Aleshin P. Sound emitters of the firm "Ningbo East Electronics Ltd."//Circuit engineering. - 2002. No. 6. - P.57.
4. Butov A. Converter 220...220 V // Radiomir. - 2002. - No. 4. - p.8.

Author: A.L. Butov

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