How To Use An Electrical Relay

A relay is an electromechanical device used for switching heavy electrical loads in response to relatively lower input signals.

It can be recognized as a square block of different sizes, depending upon the make and the specs of the particular relay.

Commonly the SPDT type of relays are used for the transfer of electrical power from a low to high.

Basically there are five pins in the above types of releyas. Two of them are the coil leads, across which the coil ends are soldered. Among the remaining three leads, one is the pole which moves in response to the magnetic field created

by the coil.

[Are you looking for a custom built circuit for a specific application, feel free to post it HERE]
One end of this pole is fixed and constitutes the lead while the other end makes contact with either of the two fixed points which are
called normally closed terminal and the normally open terminal, so in addition to the coil leads we have one pole lead and two fixed leads designated as normally colsed NC and normally open NO.

As the name refers to normally closed point remains connected to the movable pole and thus the leads of the NC point and the lead of the pole may show continuity when no power is applied to the relay, however once the coil is nergized, the pole moves and connects with the NO point disconnecting  from the NC point and vice versa.

The explanation makes it clear how to use an electrical relay and how the relay functions. 

Article Written By Swagatam

Swagatam is a blogger at

Last updated on 30-07-2016 243 0

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