# How to Connect Relay in Circuit?

In this tutorial we are going to learn about How to Connect Relay in Circuit?

As per below image of relay can see there is generally five pins like this:

1. NO (Normally Open)
2. NC (Normally Close)
3. C   (Common)
4. Coil +(Positive Volt)
5. Coil -(Negative Volt)

As per above image for Relay can see common pin, this pin is connected with centre pole of the relay which moves in response to coil voltage ON/OFF switching.

As per above image for Relay can see normally close pin, this pin is connected with normally closed contact. Normally closed refers to the internal connection of this pin with the pole of the relay.

As per below image for Relay can see normally open pin, this pin is connected with the normally open contact. Normally open refers to the internal open connection of this pin with the pole of the relay. However when the coil is energized, this pin connects with the pole while the other normally closed pin disconnect.

As per above image for Relay can see normally coil pins, A diode must be connected across the relay coil to allow safe discharge of the reverse current stored inside the coil, as soon as it is switched OFF.

As per above image for Relay can see normally coil + pin, +DC cathode side of the diode should be connected to the positive supply, and this supply should match the relay coil voltage specs, Example 12V for a 12V relay.

Working of Relay :

In below circuit can see, A transistor driver is generally applied for switching a relay ON/OFF as depicted here, A positive trigger at 1K end actuates the relay and vice versa.

Relay Load, in circuit can see, the load which is a light bulb and the input 220V can be changed as per specification.

When apply a positive trigger to the transistor base .When the switch is closed positive supply triggers the transistor, which operates the relay coil, pulling the contact N/C to N/O. due to this immediately toggles ON bulb, as the 220V connects the bulb through the N/O and pole contact.

When switched OFF, the relay reverts to its earlier form.