HomeCircuitsOver voltage and Under Voltage Protection Circuit Diagram

# Over voltage and Under Voltage Protection Circuit Diagram

- # Introduction:

The Under Voltage and the overvoltage protection circuit is a circuit which protects you from The higher Voltages and the Lower Voltages Conditions. For the Lower Voltage, You can see some flickers in the Lights. And for the higher voltage one, the Circuit will be fully damaged. This is because of the High Potential. In particular, Cases Like If a Motor is Running in Low voltage then the Coil of the Motor may Burn. This circuit will Disconnect all the connected appliances When there are Lower and upper voltage situations.

watch the youtube video for more detailed instructions.

## Few Things about Upper and Lower Voltage Protection Circuit:

1.  This is a Basic Circuit Based upon Dual comparator IC
2. The Circuit needs 2 input. One is a Constant 12V input for running the circuit. and another is a Variable Sense voltage. This variable voltage senses the voltage whether it is High or Low.
3. A relay is connected in such a way that if the voltage is in a certain limit then only the relay will be on. and if the voltage is higher? lowe then the relay will be off.
4. One of the comparators of LM393 is used for setting lower threshold voltage and the other one is used for setting higher threshold voltage by rotating the potentiometer.
5.  Now the red LED indicates the higher voltage yellow LED is for lower voltage.
6.  In both cases, the relay will be off. but if the voltage is in a certain limit then only the green LED lights up and the relay will be on for external loads.

## Circuit Schematics:

Here is the basic schematics of the Upper / Lower Voltage Circuit.  I have made the Circuit Diagram by using EasyEDA.com.

## How the Upper/ Lower Voltage Works?

1. LM393 has 2 Comparators. one of the comparators is sensing the Higher voltage and another comparator is sensing the Lower Voltage.
2. For setting the Threshold we have used two potentiometers.
3. Rotate the Potentiometer and set the voltage range for the operation of the circuit.
4. we are using a Transformer for the sense voltage. We all know that the transformer has a certain turn ratio. Let’s Determine transformer has 220V Primary and 12V secondary.
5. Now in General situations when the line voltage is 220V then the Secondary voltage of the Transformer will be 12V.[It will be the rated voltasge]
6. Suppose a Low Voltage Situation when the voltage is around 180V. In this case, the primary voltage of the transformer is low. Gradually the secondary voltage of the transformer will be Low. Now the Tricky part Now we will set this low Voltage secondary output as the Low set voltage.
7. Just apply the same process for the High Set Preset. Let’s Determine that Linne voltage has increased up to 300V.  In this case, the Primary is 300V. Not it is Obvious that the secondary voltage will be higher. At next wee will use this secondary voltage and set it as the High Set threshold.
8. In this, we have added the Higher and the Lower voltage values in the Comparators. Now the Comparator Compares the voltage and Turns on and off the relay according to the voltage.

## Several Important Notes:

• When the line voltage is higher than the transformer’s rated voltage then the transformer will produce more heat. In some cases, the Transformer may be damaged. This is because of the transformer turn Ratio. The Transformer was made for 220Volts, not for 300V. So it means the turns ratio is for the 220v.
• So, my point is if you want to Give the circuit Longlife then I will suggest you make a custom turn ratio transformer. where the transformer can handle the 300V easily.
• Now for Powering the circuit, I will Suggest you use an SMPS. Because the Smps is the only Powersupply that can give constant regulated power to the board.

## PCB Making:

1. The Circuit Has many Components. So, I decided to make a Prototype PCB for the schematics.
2. I have used EasyEDA for Making the PCB. Then I generated the Garber files for the PCB.
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