Simple Mains High Low Voltage Cut-off Circuit

In this circuit we'll learn about a simple high low voltage cut off circuit with alarm which can be used for protecting all 220V or 120V operated appliances.

This straight forward circuit will shield electrical apparatuses from over voltage and also under voltage. The circuit likewise delivers a caution when power returns. A perfect circuit for home to shield your significant gears from voltage vacillations. The same circuit with a few alterations can be utilized to make a programmed voltage stabilizer.

At the point when the mains voltage is in the typical level, the voltage at the negative terminal of zener diode D4 will be under 5.6 Volts. At this condition transistor T1 won't lead. The same time voltage at the negative terminal of zener diode D5 will be more noteworthy than 5.6 thus the transistor T2 will be directing. The transfer will be enacted and the green Drove will be shining.

At the point when the mains voltage is higher than as far as possible the transistor T1 gets to be leading following the voltage at the negative terminal of D4 is more noteworthy than 5.6 V. In the meantime transistor T2 will be non leading which brings about the deactivation of relay to cut the mains supply from burden. At the point when the mains voltage is not exactly as far as possible transistors T1 & T2 gets to be non channeling making the transfer to de-actuate and cut the heap from mains.

The clock NE555 is wired as a monostable multivibrator with a clock width of 10ms. When the power returns after a cut off a negative voltage is gotten at the trigger pin which triggers the IC NE555. The transistor T3 gets forward biased and it drives the bell to deliver a beep as a sign of mains resumption. Additionally the transistor T1 is made on which thus makes T2 off. Therefore the relay transfer will remain de-actuate for 10ms and this gives the sufficient postponement and the supplies is shielded from surge voltages.
Notes.

To balance the circuit an autotransformer is required. Join the wires of autotransformer to the transformer mains terminals.

Set the voltage to 260V and conform VR1 to make the relay deactivated.

Presently set the autotransformer to 160V and conform VR2 with the goal that the transfer is de-invigorated.

VR3 can be utilized to change the volume of bell.

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