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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Voltage relay with audible alarm. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Protection of equipment from emergency operation of the network, uninterruptible power supplies Permissible fluctuations of alternating voltage in a household electrical network 220 V - ± 5%. A more significant increase in voltage can lead to failure of consumers of electrical energy. In cities, compared to villages, the electrical network is more stable, which is ensured by the presence of numerous compensation substations, whose powerful transformers equalize "voltages with changes in energy consumption. However, despite this. in the evening and at night, especially in summer (when heating electric devices) due to a natural decrease in electricity consumption (everyone is sleeping), the voltage in the network can increase to 245 - 250 V. Knowing this, you can ensure the safety of electrical devices in your home. It is almost impossible to constantly visually "monitor" the electrical network (for example, by reading the readings of a voltmeter plugged into a 220 V socket). For these purposes, I propose to use an audible signaling device, the circuit of which is shown in the figure.
If the mains voltage exceeds 230 V, a loud melodic sound signal will sound. Next, you should immediately disconnect electrical devices from the network, leaving only lighting lamps (you can still put up with their failure - "burnout"). The simplicity of the device, the diagram of which is shown in the figure, makes it accessible for burning, and the skilled hands of a radio amateur can create an effective device that signals an unacceptable voltage in the home electrical network and takes measures to disconnect consumers from it. The device is implemented on the KR1436AP1 chip (foreign analogue of KA2410). Today, it can be purchased at radio parts stores relatively inexpensively (7 - 8 rubles per copy). In terms of functionality, cost and versatility of use, it resembles the popular KR1006VI1 microcircuit; they both have a compact DIP-8 molded plastic package with a two-row pin arrangement. This makes it convenient for printed wiring of electronic components. As part of the KR1436AP1 microcircuit, functionally designed for the buzzer of an analog telephone set. includes several electronic components. This is a Schmitt trigger - a signal shaper, two pulse generators with a frequency ratio of 1:25 (the parameters are adjusted by external RC elements). output amplifier and reference voltage source. The last node provides power modes and stabilizes the operation of the generators and the output amplifier. The external power supply voltage of the circuit can vary in the range from 5 to 29 V. moreover, it can be unstabilized. Consider the electrical parameters of the KR1436AP1 microcircuit. The output voltage (with an external power supply with a maximum voltage of 29 V is 17 - 21 V. The maximum allowable load current is not more than 35 mA, which allows you to connect even a low-power electromagnetic relay of the RES-15 type to the microcircuit output. Output resistance (impedance) 200 300 Ohm .Power dissipation 0,4W. Since the main purpose of this microcircuit is to work in an analog telephone line, inside the "black box" - the DIP-8 case, there is a Schmitt trigger with hysteresis. The threshold for turning on the internal components of the microcircuit depends on the external applied DC voltage. In the classic version, the trigger voltage ranges from 17 to 21 V, while the holding voltage (the threshold at which the internal components of the microcircuit are de-energized) is 9,7 12 V. This switching mode of the KR1436AP1 is recommended by the developers. Pin 2 of the chip remains free. Consider the diagram of the signaling device. An alternating voltage of 220 V is constantly supplied through the limiting resistors R1 and R2 to a rectifier diode bridge consisting of diodes VD1 - VD4. The relatively high resistance of the limiting resistors at the input of the circuit is due to the low current consumption of the node (2 mA and 5 mA in idle and sound alarm modes, respectively) . The insignificant current consumption in the sound signaling mode is explained by the use of the ZP-18 piezoelectric emitter (ZP-Z, ZP-25 and similar can be used). The voltage rectified by the diode bridge is smoothed by the oxide capacitor C1 (K50-12, K50-20, K50-35 and similar) and stabilized by the VD5 zener diode. When a voltage less than the threshold value arrives at the DA1 microcircuit, the internal stabilizer does not supply voltage for the remaining components of the microcircuit, since the threshold value of operation is 17-21 V, and the maximum supply voltage in accordance with the nameplate electrical characteristics is 29 V. When the mains voltage increases above 230 V, a constant voltage of 1 V or more will be supplied to pin 1 of DA17, as a result of which emitter B1 will generate an audible signal. A significant excess of the voltage in the 220 V network is not dangerous for the node, since a VD5 zener diode is installed at the input of the microcircuit, which turns on when the DC voltage exceeds 27 V and stabilizes this voltage, protecting the microcircuit. Instead of the KS529A zener diode, in extreme cases, you can use the D816V zener diode. According to the rules for the inclusion of zener diodes. VD5 can be composed of two series-connected devices such as D814D or KS213Zh. Then the stabilization voltage of the zener diodes adds up. Inside the KR1436AGP chip there is a power supply unit with hysteresis. This means that it is enough for the voltage to rise at least once to the threshold value at the DA1 input. so that the chip generators turn on. And they will turn off, like all other nodes, when the supply voltage at the input (pin 1) decreases to 9.7 - 10 V. This property of the microcircuit is especially valuable, since it allows you to fix even a single power surge in the network in order to take appropriate security measures . "Forewarned is protected". When the threshold voltage in the DA1 chip is exceeded, two internal generators implemented on Schmitt triggers start working. The first is formed by a trigger and a C2R3 circuit, the second also consists of a trigger and a C4R4 timing circuit. Infra-low frequency pulses (0,5 - 1 Hz) from the first generator control the operation of the second. The influence of the first generator is that the pulses of the two generators appear alternately at pin 6. Such a mixed signal is two-frequency. This two-frequency signal will sound the piezoelectric emitter B1 when the voltage in the AC network exceeds 230 V. To stop the sound, it is necessary to interrupt the power supply of the device for a short time by disconnecting it from the mains. When the signaling device on KR1436AP1 often turns on in the audible warning mode, evidence of repeated mains voltage surges, it is necessary to think about eliminating the very causes of mains voltage instability. The consequence of delay and inaction in this case may be the failure of expensive appliances: refrigerator, TV, music center, etc. The adjustment of the device is reduced to the precise setting of the threshold for the operation of the electronic assembly, assembled according to the above scheme. It is advisable to do this in the late evening or at night, when the voltage in the network increases. A DC voltmeter is connected to the output of a diode rectifier assembled according to a bridge circuit. Parallel to the mains outlet - AC voltmeter. By changing the resistances of resistors R1 or R2, stable switching on of the microcircuit generators is achieved at a network voltage of 230 V or more. When the resistance of one of the limiting resistors decreases, the signaling device becomes more sensitive to an increase in the mains voltage and vice versa. Piezoelectric emitters of the ZP type have a characteristic dependence of the radiation power (sound loudness) on the frequency of sound pulses. Therefore, it is possible in the same device to achieve an increase or decrease in the volume of the emission of an audio signal. With the values \u22b\u47bof the elements indicated in the diagram, the volume of the sound will be sufficient to be heard several meters away (in another room). By changing the resistance of the resistor R4 within 1 - XNUMX kOhm, it is possible to tune the internal oscillator of the microcircuit to the resonant frequency of the emitter BXNUMX. while the volume of the sound increases significantly. All fixed resistors are of the MLT type. Diodes VD1-VD4 - type KD105B, KD243A-KD243G. you can use diode assemblies KTS402A. KTS407A. KTS405A. Capacitors C1, C2 - oxide, type K50-35. The remaining capacitors are ceramic, type KM or similar. The body of the device is plastic; in the author's version, the body of the network adapter is used, in which a step-down transformer was previously placed along with a stabilizing unit. The installation of elements is arbitrary. The use of such a device, which reacts even to short-term power surges in the network, will help prevent the failure of expensive electronic equipment that is left connected to the network around the clock. Attention, important! Since the device uses a transformerless power supply, the common wire of the device must not be grounded! Author: A.Kashkarov
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