FOREWARNED IS PROTECTED

WARNED — IS PROTECTEDPermissible variation of AC voltage in household electrical network In the 220 — ±5 %. A more significant increase in voltage may result in damage to consumers of electric energy. In the cities, compared to villages, mains is more stable, which is ensured by the presence of numerous compensation substations, powerful transformers which equalize” voltage with changes in energy consumption However, in spite of it. in the evening and night hours, especially in summer (when not in use electric heating devices) due to the natural reduction in electricity consumption (all asleep), the voltage could rise to 245 — 250 V.

 
Knowing this, you can ensure the safety of electrical devices in your home. Constantly visual to “follow” electric network (for example, a reading of the voltmeter plugged in 220V) is almost impossible. I propose for this purpose to use an audio signalling device, scheme of which is presented in the figure.
 
When exceeding the voltage more than 230 In will sound loud melodious beep. Next, you should immediately disconnect the electrical device from the network, leaving only the lighting of the lamp (the failure of “burnout”, you can still accept). The simplicity of the device, scheme is presented in the figure, makes it available for VOC combustion, and skilful hands Amateur radio operator can build an effective device that signals invalid voltage for home electrical and the adoption of measures to disconnect users.
 
The device is implemented on the chip КР1436АП1 (foreign analogue КА2410), in shops of radio components it is possible to purchase relatively inexpensive (7 — 8 rubles. for instance). In functionality, cost and versatility it resembles a popular chip КР1006ВИ1 they both feature the compact housing of molded plastic DIР-8 with two-row arrangement of conclusions. This makes it convenient for printed wiring electronic assemblies.
 
In the composition of the chip КР1436АП1 functionally designed for buzzer analog phone. includes several electronic components. This Schmitt trigger — a signal generator, two pulse generator with frequency ratio 1:25 (the parameters adjusted by the external RC-elements). output amplifier and voltage reference. The latter unit provides the modes and stabilizes the generators and the output of the amplifier. The voltage of the external power supply can vary in the range from 5 to 29 V. it can be unregulated.
Consider the electrical parameters of the chip КР1436АП1. Output voltage (with external power source with a maximum voltage 29 is 17 — 21 V. the Maximum load current less than 35 mA, allowing you to connect the output circuits even low-power electromagnetic relay type RES-15. Output resistance (impedance) 200 to 300 Ohms. The power dissipation of 0.4 watts.
 
As the hook the main purpose of this chip — it is a work in analog phone lines inside the “black box” — housing DIР-8, placed a Schmitt trigger with hysteresis. The trigger threshold for internal nodes of the chip depends on the external applied DC voltage. In the classic version of the triggering voltage ranges from 17 to 21, despite the fact that the holding voltage (the threshold at which the internal nodes of the chip are de-energized) is 9.7 12 V. This actuation mode is recommended КР1436АП1 developers. The terminal 2 of the chip remains free.
 
Consider the diagram of the device of the alarm device. Alternating voltage of 220 V is constantly supplied through a current limiting resistors R1 and R2 to the diode bridge rectifier composed of the diodes VD1 — VD4 to the Relatively high resistance of restrictive resistors at the input of the scheme is due to the low current consumption of the node (2 mA and 5 mA in modes of peace and chime, respectively). Slight current consumption in the alarm sound mode is due to the use of piezoelectric transducer SN-18 (you can apply SN-W, SN-25 and similar).
 
Rectified diode bridge voltage is smoothed by the capacitor C1 oxide (K50-12, K50-20, C50-35 and similar) and stabiliziruemost a Zener diode VD5.
 
When applying for a microcircuit DA1 a voltage less than the threshold value of the internal stabilizer is not producing the supply voltage for the remaining nodes of the chip, since the threshold triggering 17-21, and the maximum supply voltage in accordance with the nameplate electrical characteristics is 29 V.
 
Circuit diagram of beeper high voltage household power
 
A circuit diagram of beeper high voltage household power
 
If you increase the voltage above 230 V on pin 1 DA1 receives a constant voltage 17 and, consequently, the emitter of Q1 will generate a beep. A significant excess of the mains voltage of 220 V for a node not dangerous, as input circuits includes a Zener diode VD5, which is turned on when excess DC voltage is above 27 and stabilizes this voltage, protecting the circuit. Instead of the Zener diode КС529А, in a pinch, you can use Zener Д816В. According to the rules of inclusion of the Zener diodes. VD5 can be composed of two series-connected devices of the type Д814Д or КС213Ж. Then, a voltage stabilizing Zener diode is formed.
 
Inside the chip there are КР1436АГП supply unit with hysteresis. This means that sufficient voltage at least once to grow to the threshold at the entrance of DA1. to the generators of the chip involved. And they will turn off, as all other nodes, while reducing the supply voltage at the input (pin 1) to 9.7 — 10 V. This property of the chip is especially valuable because it allows you to record even a single jump of voltage in the network in order to adopt appropriate security measures. “Forewarned is protected.”
 
If the threshold voltage in the chip DA1 begin to work two internal oscillator implemented with a Schmitt triggers. The first is constituted by a trigger circuit C2R3, the second consists of a trigger and timing circuit C4R4. Pulses of infra — low frequency (0.5- 1 Hz) with the first generator drive the second. The impact of the first generator is that terminal 6 appear alternately pulses the two generators. The mixed signal is a dual-frequency. This dual-frequency signal and will sound the piezoelectric emitter of Q1 when voltage at the AC over 230 V
 
To stop sound you need for a short time to break the purpose of the power device, disconnect it from the network.
When switch on КР1436АП1 is often included in sound mode warning evidence of repeated surges in the mains voltage, you need to think about eliminating the actual causes of instability of the mains voltage. The consequence of delay and inaction in this case could be the failure of expensive equipment: refrigerator, TV, stereo, etc.
 
Establishing device is reduced to the precise setting of the threshold electronic unit assembled according to a given scheme. It is desirable to do in the late evening or at night, when increasing the voltage.
 
The output of the diode rectifier assembled in the bridge circuit, connect a DC voltmeter. Parallel to a wall outlet — AC voltmeter. Change resistor R1 or R2 to achieve a stable incorporation of the generators of the chip when the voltage of 230 V and more.
 
Decreasing the resistance of one of the limiting resistors, the indicator becomes more sensitive to the mains voltage increase and Vice versa.
 
Piezoelectric transducers of type ZP have a characteristic dependence of the radiation power (sound volume) of the frequency of the sound pulses. Therefore, it is possible in one and the same device to increase or decrease the volume of the radiation sound When specified in the diagram element values the sound volume is enough to hear it a few feet away (in another room). Change in the range of 22 — 47 kOhm of the resistor R4 cannot configure internal oscillator of the chip at the resonant frequency of the emitter Q1. the volume of the sound increases significantly.
 
All constant resistors of MLT type. Diodes VD1—VD4 — type КД105Б, KD243A—КД243Г. it is possible to use diode assemblies КЦ402А. КЦ407А. КЦ405А. Capacitors C1, C2 oxide, type K50-35. The remaining ceramic capacitors, the type of KM or similar.
 
The device is made of plastic; in the original use case of the network adapter, where you have previously posted a step-down transformer with a stabilizing node Mounting elements may be arbitrary.
 
The use of such devices responsive even on a short-term surges in the network, will help to prevent failure of expensive electronic equipment, leave the clock plugged in.
 
Attention!
 
Since the device uses a transformerless power supply, the common wire of the device to ground is impossible!
 
A. KASHKAROV, St. Petersburg

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