What is a Relay?
A Relay is a Electromechanical switch which uses low voltage to switch higher voltage applications. Basically, a Relay is a four pin or a five pin(based on the type) device which consists of a tiny coil, a small spring, contact metal. The 2 pins of the Relay are connected to the tiny coil which magnetizes itself when it is energized by an external voltage. The other 3 pins are INPUT, normally opened, normally closed.
Types of Relay:
Relay comes with various types according to its usage.
For switching low current applications we can use normal relays like this
For switching high current applications we can use high current handling relays like this
which handles high current.
Types of pin in a Relay(5pin Relay):
Coil pins
INPUT pin of a Relay
Normally opened pin of a Relay
Normally closed pin of a Relay
Coil pins of a Relay
Coil pins of a Relay is connected to the coil inside the Relay which magnetizes the metal contacts in order to switch the output. we should give 5V for the coil in a 5V relay and a 12V for the coil in a 12V Relay. A normal 5V Relay consumes about 45-55mA of current. And A normal 12V consumes about 80-150mA of current, but these current values can vary according to the design and usage of the Relay for various purposes.
Common pin of a Relay
A Relay consists of two circuits coil circuit and the switching circuit. The coil circuit has 2 input pins. The switching circuit has 3 pins. Among the 3 pins one is the common pin which is common to both normally closed and normally opened pins. In this common pin the input voltage will be given in order to switch to the output through normally closed pin or normally opened pin.
Normally closed pin of a Relay
The normally closed pin of a Relay directly have contact with the INPUT of the Relay. This means that the Relay acts as a closed circuit even though the Relay coil is in OFF position.
Normally opened pin of a Relay
The Normally opened pin of a Relay does not have contact with the INPUT of the Relay. This means that the Relay acts as a open circuit when it is not energized but at the same time it acts as a closed circuit when it is energized.
By using the Normally opened pin of a Relay we can turn OFF and turn ON any appliances or motors.
Usage of Relays
Relays are widely used in controlling applications which operates by higher voltage or higher currents.
It is used in motor bikes for self starting motor, blinking of indicator lights, switching of headlight high beam and low beam etc.
It is used in automobiles like cars to switch the self motor or crank motor, switching head lights, hazards lights, wiper motor etc.
In automated homes, relays are used to switch home appliances automatically.
The bigger size relays are used to switch street lights and highway lights automatically by using a timer circuits which turns ON during night time and turns OFF during day time.
Have fun :)
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