Your costly electrical and electronic equipment to be cut over / under voltage to save from the harmful effects of very high and very low mains voltages.
The circuit has auto reset and utilities readily available components. It makes use of the comparators in Timer IC 555 Power is extracted to achieve a reliable operation of various parts of the power supply circuit of the relay and the control circuit .
Is held , the utility loop 2 while comparator 1 output ( connected to reset pin R ) is low by shorting pins 5 and 6 of the IC 555 are positive input of the comparator is a two 1/3rd of the voltage Vcc. As a negative input terminal 2 is less positive than 1/3rd VDC, the output of the comparator is high and the two built-in switch = set, its Q output (pin 3) is high. At the same pin 7 is in a high impedance state and the LED is connected to pin 7 is thus turned off. The output ( pin 3) reverses ( goes low) when pin 2 taken positive than 1/3rd of Vcc . At the same time pin 7 goes low ( output Ǭ internal flip- flop is high) and the LED on pin 7 is ON . Both timers (IC1 and IC2) are configured to operate in the same way. PresetVR1 fits under voltage ( eg 160 volts) cut by observing that LED1 is lit only when the offer slightly higher than 160 V AC.
In this regard, the output on pin 3 0f IC1 is low , the transistor T1 and the OFF state. As a result RESET pin 2 of IC2 remains high as it is connected to Vcc 100 kilo - ohm resistor R4.
Preset VR2 is adjusted over voltage (eg 270 V AC) by the observation that only LED2 turns off when the power is cut slightly less than 270V AC . Use the RESET pin 4 of IC2 high, the output pin 3 is also high. As a result, T2 leads and power relay RL1, connecting load on the network via its N / O This is the case when the supply voltage exceeds 160 V AC, but less than 270 V AC .
When the supply voltage exceeds AC 27oV causes output pin 3 of IC2 goes low and T2 cut- relay RL1, in spite of the RESET pin 4 is high. If the supply voltage drops below 160 V AC, 3 - Pin IC1 high and LED1 is turned off. The 3 - pin high performance results of the transistor T1 and reset pin 4 of IC2 are pulled low. Therefore, IC2 output is low and transistor T2 does not conduct. As a result, RL1 is energized, whereby the load is disconnected from the power supply. When the voltage increases over 160 V (but less than 270 V AC) , to the load connected to the power supply for energizing the new relay.