Automotive Relays - What Are They And Why Do You Need Them? What is a relay? A relay is an electromechanical or electronic draw through which a heavy load

can be switched ON & OFF with a nominal input of recent & voltage. This article

focuses on electro-mechanical relays passe in automotive applications.

How does a relay work?

The utility and function of a relay can be best understood by thinking of a lever.

A lever is inserted at a corner of a heavy load and by placing a wedge (fulcrum)

under the lever, the heavy load can be easily lifted by a runt amount of exertion.

Similarly, a heavy electrical load drawing heavy recent can be switched on & off

by applying a slight amount of unusual through a coil(solenoid) . What happens is

this - the coil gets magnetized with the new and attracts or repels a

plunger(a rod passed through the coil) . The attracting or repelling of the plunger

either connects two switching contacts in the relay (also known as NO or Normally

Open/Single Throw/Form A) or separates them (NC or Normally Closed/Double

Throw/Form C), as required. As soon as the energisation of the coil is stopped,

the main contacts go serve to their novel residence.

In automobile applications relays of different configurations with single or

multiple contacts are worn for different applications.

Why is a relay required?

Apart from switching a circuit with heavy load, on & off, a relay is required to

1. Conserve energy

2. Prolong the life of device

3. Improve the efficiency of a procedure.

For example let us remove the switching of two headlamps of an automobile. If the

same is switched on through a normal switch at the dashboard, the voltage plunge

from the battery to the lamps through the switch will be vast and the heat

generated in the circuit due to resistance will be much. The heavy unusual

will be drawn by the lamps which will not only heat the circuit but also drain the

battery heavily.

To give an example of the attain of voltage topple, a chart is given below:

Operating Voltage. incandescent Intensity of a Lamp.

100% 100%

95% 83%

90% 67%

85% 53%

To switch on a 12V-60/100 Watt Halogen lamp, a typical 12V Relay allows a voltage

drop of only 0.02V and the coil recent is only 2 milliamps.

Another critical function of the relay is hasty switching off(0.05Sec Max.) . The

more time the contacts of a switch prefer to crash at chubby load, the more sparks

will be generated due to electromagnetic attain on contacts in a switched on

state. Prolonged sparking will mean more wear of the contact points and the effort

of contacts melting and generating a fire. International standards have very stringent relay specifications. The endurance of a relay is generally specified in millions of switching operations.

Where should a relay be installed?

Wherever manual switching has been musty for express switching of a Lamp or Motor or

any gadget exceeding 10 Amps of load, a splendid relay must be build in the circuit.

It is best if the relay can be kept as reach as possible to the load (but not in a hot situation surrounding come the engine)

How should a relay be installed?

1. Wires connected to the manual switch should be connected to any Coil terminal

of the Relay.

2. The load should be connected to any one contact terminal of the Relay (unless

Positive/Negative are specified) and the other to the definite terminal of the

battery (for Negative Ground circuit), with an appropriate Fuse.

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