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How Does A Relay Work?!!

posted Jul 31, 2017, 7:48 AM by Rohit Bhaskar   [ updated Jul 10, 2018, 11:30 AM by Chirag Trasikar ]
For a lot of engineers this post might just be like twilight ( useless and a complete drab. No offense to twilight fans!! or i might just get up tomorrow with people pelting stones at me…). But for many others this post might just come in handy.


Before we get to how a relay works, lets see what it does and what is it used for. The most simple definition is that a relay is an electrically operated switch. Relays use an electromagnet to mechanically operate a switch. They are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal.

The following video will tell you the basics of its working


As you saw, a relay consists of two separate and completely independent circuits. The first is at the bottom and drives the electromagnet. In this circuit, a switch is controlling power to the electromagnet. When the switch is on, the electromagnet is on, and it attracts the armature (blue). The armature is acting as a switch in the second circuit. When the electromagnet is energized, the armature completes the second circuit and the light is on. When the electromagnet is not energized, the spring pulls the armature away and the circuit is not complete. In that case, the light is dark.


There are different types of relays based manufacture and working. You can see all thee types of relays on the wikipedia page….HERE

Relays are found hidden in all sorts of devices. In fact, some of the first computers ever built used relays to implement Boolean gates. Relays are used in electronics to switch a smaller current which in turn will control larger current. They prevent the user to have direct contact to the main device being controlled that might be holding high voltage. These devices are comparable to a remote control which is used to make a big electronic equipment work. Relays are being applied at home, industries and even on the street!! Another application of relays is that it is used in automobiles as control switches for the ecu (engine control unit).