Over Voltage Protection Circuit, Auto Cut Circuit

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Over Voltage Protection circuit diagram

This Over Voltage Protection Circuit is very easy, simple and very useful.

Only one transistor and some other components are used in this overvoltage protection autocut circuit.

How to Connect the load:-
load is connected with NC (normally connected) pin of relay.

This Over Voltage Protection Circuit is a very useful auto cut circuit to the protection of any electrical or electronics appliances from high voltage. If any device needs 12volt to work properly than this can be damage by increasing the voltage. This Over Voltage Protection Circuit automatically cuts the current supply to any appliances from the input circuit. And when the voltage decreased at  normal level then automatic on the supply is. So it helps to protect the circuit from damage by the high voltage. If you use this circuit for auto cut on over 6volt then use a 6volt relay and the circuit need 6volt

Before using this circuit set the preset and check the relay or output to at which input voltage level relay gets activated. Increase and check the input voltage by multimeter and set the reset at the required position. This Over Voltage Protection Circuit can be used at both AC and DC appliances because it use a relay, but this circuit work only on AC power supply.

Working of Over Voltage Protection circuit

Over Voltage Protection Circuit, Auto Cut Circuit

At first, when the voltage is under or below the maximum limit ( at which it is adjust) the maximum voltage dropped through the resistance R2 to the ground and the base of transistor does not get enough power to switch on the transistor.

At this stage, the trangister is an off state, and really does not get supply and it is not activated.

When the input voltage of this circuit is increasing and cross a level then the input voltage through register R1 and preset also increased and when after dropping the voltage throw R3, enough

amount of voltage is the best of the transistor turned on it and supply passed between ammeter and collector.

Now relay is activated and the supply is disconnected to the appliances. And that is protected from high voltage supply.

Before using it should be adjusted by preset and tested the input voltage and set required the auto cut level according to suitable.


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Types of over-voltage protection

As with many electronic techniques there are several ways of implementing a particular capability. This is true for over-voltage protection.

There are several different techniques that can be used, each with its own characteristics. Performance, cost, complexity and mode of operation all need to be weighed up when determining which method to use during the electronic circuit design stage.

All three techniques are used and can provide effective power supply over-voltage protection. Each has its own advantages and disadvantages and the choice of technique needs to be made dependent upon the given situation.

Component list

PartsValueQuantity
Transformer12V 1A1
TransistorBC1471
Capacitor1000uf 35V1
DiodeIN40071
Rasistor2.2K1
Rasistor33K1
Preset5K1

Power supply over-voltage protection is really useful – some PSU failures can put damaging large voltages on the equipment. Over-voltage protection prevents this happening on both linear regulators and switch mode power supplies.


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