Over Voltage Protector

Over Voltage Protector

The problem of voltage fluctuation is common which some time passes high voltage may destroy electrical appliance. To overcome this type of problem the team of dreamlover technology design a simple but effective circuit over voltage protector, protects electrical appliance from over voltage. The logic of over voltage protector is so simple.

Circuit Description of over voltage protector

The whole circuit of over voltage protector is build and fabricated around operational amplifier used as comparator. The inverting input is given to pin 2 of op-amp IC (IC1) with reference voltage of 5.1V from zener diode. Similarly, non-inverting input is given to pin no 3 of IC1 use as sensor for over voltage protector for sensing voltage fluctuation in the mains. The two transistors T1 and T2 conduct alternating (i.e. one at a time) according to the voltage of mains. When voltage is around or below 240V AC transistor T1 is in off-state where T2 energized relay RL1. Similarly, when voltage becomes beyond 240V (i.e. above 240V) T1 is in conducting-stage and T2 is in off-stage which de-energized the relay RL1 and switch-off the appliance.


Resistors (all ¼-watt, ± 5% Carbon)

R1 = 147 Ω/2W

R2 = 100 Ω/1W

R3 = 330 Ω

R4 = 100 KΩ

R5 = 1.8 KΩ

R6, R7 = 1 KΩ

VR1 = 10 KΩ

VR2 = 22 KΩ


C1, C4, C5 = 0.01 µF

C2 = 1000 µF/25V

C3 = 100 µF/25V


IC1 = µA741 (Operational Amplifier)

IC2 = 7812

T1= BC547

T2 = SL100

D1, D2, D3, D4, D5 = 1N4007

D6 = 1N4148

ZD1 = 5.1V zener diode


X1 = 230V AC primary to 7.5V-0-7.5V, 1A secondary transformer

RL1 = 12V, 200Ω 1 C/O Relay


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