Protection against over voltage under voltage using oamp

Over voltage & under voltage

protection circuit

Over voltage & under Voltage protectionThe above circuit is protected against when voltage is high & low.

Sl no. Name of the Component

Specification Quantity

1. Transformer 230/12 v ,600 mA

1

2. Diode 1N4007 53. Capacitor 100µF, 25v 14. Resistance 470 & 1K ohms 35. Potentiometer 10K 26. Zennor Diode 3v 27. Transistor BC547 28. Relay 12v, S.P.D.T. 1

Transformer A transformer is a static electrical Device that transfers energy between two or more circuits

through electromagnetic induction.A varying current is the transformers primary

winding creates a varying magnetic flux in the core and a varying magnetic field at the secondary

induces a varying electromotive force (EMF) or voltage in the secondary winding. Making use of Faradays' Law in conjunction with high magnetic permeability. Core properties, transformers can

thus be designed to efficiently change AC voltages from one voltage level to another with power

networks.In this project 230/12 volt 600mA transformer has

been used.

DiodeIn electronic, a diode is a two-terminal electronic

component with asymmetric conductance; the name of the two terminals are anode & cathode.

The most common function of a diode is to allow an electric current to pass in one direction (called the diode’s forward direction), while blocking current in the opposite direction (the reverse direction).

The unidirectional behaviour is called rectification, and is used to convert alternating(AC) current to

direct current(DC). In this circuit diode is use for convert AC to DC

supply. We use 5 number of diodes which is 1N4007

CapacitorA capacitor (originally known as a condenser) is a passive two-terminal electrical component used to store energy electrostatically in an electric field. Capacitor are widely used in electronic circuit for

blocking direct current(DC) while allowing alternating current(AC) to pass. For this, we can

use capacitor like a filter circuit. We use 100µF 25 volt electrolytic capacitor.

ResistorA resistor is a passive two-terminal electrical

component that implements electrical resistance as a circuit element. Resistor act to reduce current flow, and , at the same time, act to lower voltage

levels within circuits. In electronic circuits resistors are used to limit current flow, to adjust signal

levels.Here we used 3 resistor one resistor is 470Ω and

other 2 is 1K Ω

Potentiometer The measuring instrument called a potentiometer is

essentially a voltage divider used for measuring electric potential(voltage). Potentiometers are

commonly used to control electrical devices such as volume controls on audio equipment. Potentiometer

are rarely used to directly control significant power(more than a watt). Potentiometer comprise a

resistive element, a sliding contact(wiper) that moves along the element, making good electrical

contact with one part of it.We used 2 potentiometer of 10K .

Zener DiodeA zener diode is a diode which allows current to

flow in the forward direction in the same manner as an ideal diode, but also permit it to flow in the reverse direction when the voltage is above a certain value know as the breakdown voltage.

When reverse bias breakdown voltage is exceeded a conventional diode is subjected to high current

due to avalanche breakdown.We used two 3.3 volt zener diodes in this project

TransistorBC547 is an NPN bi-polar junction transistor. A transistor, stands for transfer of resistance, is

commonly used to amplify current. BC547 is mainly used for amplification and switching purposes. If

has a maximum current gain of 800. The transistor terminals require a fixed DC voltage to operate in

the desired region of its characteristic curves. This is known as biasing.

RelayA relay is like an automatic switch. Here we use SPDT Relay(Single Pole Double Throw Relay) an

electromagnetic switch, consist of a coil, 1 common terminal, 1 normally closed terminal and one

normally open terminal. When the coil of an SPDT relay is at rest, the common terminal and the

normally closed terminal and the normally open terminal have continuity.

Mains over voltage and under voltage protection circuit Explained

Our mains AC domestic power may be full of ups and downs or fluctuations, which maybe quite fatal to our sophisticated appliances like TV set, DVD players, Refrigerator etc. A very simple circuit presented when installed in the house electrical may help in restricting the issue to a great extended.

Working PrincipalThe main part of the circuit is the transistors T1 & T2, which works as an inverter configuration meaning T2 responds opposite to T1.

The sensing voltage which is derived from the DC supply voltage itself is fade to the base of the T1 via pre-set P1. The pre-set is used so that the tripping thresholds can be determine precisely and the circuit understands when to execute the control action. P1 is set for detecting high voltage limits.

Initially when the voltage is with in the safe window T1 remains switched OFF & this allows the required biasing voltage to pass through P2 & reach T2, keeping it switched ON.

Therefore the relay is also kept activated and the connected load receives the required AC voltage.How ever in case suppose, the mains voltage exceeds the safe limit, the sensing sample voltage at the base of T1 also rises above the set threshold, T1 immediately conducts and grounds the base of T2.

This results in switching OFF of T2 & also the relay and the corresponding load. The system thus restricts the dangerous voltage from reaching the load and safeguards it as expected from it.

Now suppose the mains voltage goes to low T1 is already switched OFF and at the situation T2 also stops conducting due to the settings of P2, which is set so that T2 stops conducting when the mains input goes below a certain unsafe level

Thus the relay is once again tripped OFF, cutting of power to the load and prompting the required safety measures

Application of the project

The effect of over voltage & under voltage in electrical appliances is very bad. We see that each and every year many electrical appliances got damage for ups and downs of supply mains AC voltage. So our project can be used for protecting against this type of damage like -

It can be installed after the main switch by doing so it can protect against high & low voltage scenario.

We know over & under voltage is very fatal for motors, so our project can also be used for protection of motors.

It’s a safety device and in electrical engineering safety is the first priority, so we can use it where we want safety of the equipment.

This Project is made by- Ankan Biswas

Rajdip Das Shimul Majumder

Suraj Gope Subhomoy Mondal Soumyodeep Hore

Sanjit Das

The end

Amader ei project ti amader ottonto priyo bandhu Sorgio BARA k utsarga korilam. Bandhu tumi jekhanei theko shanti te theko, tomar attar shanti kamona kori…