220V Over Under Voltage Cut Off Circuit using Transistors

Two transistors and a few other simple components are all that are needed to create an efficient circuit for the mentioned precautions which may surprise some people.

What is a 220V Over Under Voltage Cut Off Circuit:

A protective electronic circuit known as a 220V over under voltage cutoff circuit is designed to keep an eye on the voltage level of a 220V power supply and disconnect the load when the voltage exceeds specified levels either above the safe operating range or below it.

This kind of circuit is frequently used to protect electrical gadgets and appliances from possible harm brought on by changes in the mains voltage.

Circuit Working:

Parts List:

According to the above circuit diagram T1 and T2 are set up as an inverter which means that T2 reacts opposite to T1 which is a simple configuration.

In simple words T2 turns off while T1 works and vice versa.

The preset P1 directs the sensing voltage which comes from the DC supply voltage itself to the base of T1.

The circuit can decide when to start control actions since the preset is used to correctly set the tripping thresholds.

Instructions for modifying the automatic preset cutoff and to identify high voltage limitations, P1 can be modified.

T1 stays OFF at first when the voltage is within the safe range enabling the necessary biasing voltage to flow through P2 and reach T2 which keeps it ON.

As a result the connected load gets the required AC voltage and the relay remains active.

However the sensing sample voltage at the base of T1 also exceeds a certain threshold if the mains voltage rises over the safe limit.

The base of T2 is right away grounded by T1.

As a result T2 the relay and the connected load are deactivated.

This method protects the load as expected by preventing the harmful voltage from reaching it.

Now T1 is already off if the mains voltage falls too low.

In this situation P2s qualities cause T2 to stop conducting as well since they are set up to do so when the mains input drops below a certain dangerous threshold.

As a result the relay goes off once more shutting off the loads power and triggering the required safety precautions.

The threshold range is somewhat wide even if the circuit is rather accurate.

This suggests that only voltage levels over 260V and below 200V or above 130V and below 100V for 120V common supply inputs allow the circuit to activate.

As a result the circuit might not be the best choice for people looking for highly accurate tripping spots and settings that they can adjust to suit what they like.

Transistors must be replaced by a few operational amplifiers to do this.

Formulas:

The below mentioned following formula is used to calculate the voltage dividers output voltage Vout:

Voltage Divider formula for T1 transistor:

V_out = (P1 / (R1 + P1)) * V_in

where:

• The output voltage is indicated by Vout.
• The resistor values in the divider are represented by R1.
• The dividers default value is P1.
• Vin is the main voltage input.

Voltage Divider formula for T2 transistor:

V_out = (P2 / (R2 + P2)) * V_in

where,

• The output voltage is represented by Vout.
• The dividers resistor values is indicated by R2.
• The dividers default value is P2.
• Vin is the voltage input.

How to Build:

To build a 220V Over Under Voltage Cut Off Circuit using Transistors follow the below steps for connections and assembling:

Assemble the parts:

• Gather all the required components mentioned as per the above circuit diagram.

Calculate the pinouts of transistors:

• Find the NPN transistors T1 and T2s pinouts.
• The emitter, base and collector are the three legs of a transistor.

Connect Transistors T1 and T2 together:

• The transistors should be connected in an inverter setup with the emitter of T2 connected to the collector of T1 and vice versa.
• Refer to the circuit diagram for help.

Join P1 and P2 Presets:

• Connect P1 to T1s base and make the necessary adjustments to detect high voltage limits.
• When the necessary biasing voltage reaches T2 connect P2 such that it stays ON as long as the voltage stays within a safe range.

Connect the Relay:

• Wire the relay to T2s collector.
• When T2 conducts this assures that the relay is turned on.

Build a preset limits:

• Check the accurate tripping thresholds for high and low voltage limits by adjusting P1 and P2.

Include Safety Measures:

• As needed include resistors, capacitors and diodes to provide constant working and component protection.

Source of Power:

• A DC power source should be connected to the circuit.

Testing:

• By turning on and off the relay one can test the circuit with different input voltages to make sure it functions properly.

Modifications:

• If necessary fine tune the circuit by modifying the default resistors for best results.

Important Information:

• Make sure all the connections are made correctly by carefully following the provided circuit schematic.
• Based on the needs of the circuit use the proper resistor, capacitor and diode values.
• When handling electrical components be careful and follow to all safety rules.
• To ensure safety and accuracy while designing the circuit it might be helpful to speak with an expert or seek advice from one if you are unfamiliar while designing electrical circuits.

Conclusion:

This 220V Over Under Voltage Cut Off Circuit using Transistors are often used to protect electronic equipment and appliances from damage in areas where voltage fluctuations occur frequently.

These type of circuits are used in a number of situations including as commercial, industrial and residential ones.

References:

Overvoltage