Relay Wiring Diagram and Connection Procedure

Hey, in this article, we are going to see Relay Wiring Diagram. A relay is a switch that connects and disconnects electrical or electronic circuits according to the electrical signals applied to it. As internal parts, it has a magnetic coil, movable open contact mechanism and closed contact mechanism. There are different types of relays available. Most have normal open(NO) contacts and normally closed(NC) contacts. So, in normal conditions, the open contacts remain open and closed contacts remain closed, but when an electric supply is applied to its magnetic coil, the open contacts become closed and the closed contacts become open.

In the below wiring diagram of the relay, you can understand how to wire a relay for your circuits. First, let's know how to choose a relay, identify terminals, and the connection procedure.

How to Wire a Relay: Procedure

There are various types of relays available in the market according to no. of pins, function, voltage-current type and ratings, and application criteria. So, first, choose which is the best for your project or circuit.

Now, time to identify the terminals or pins and their function. You can get the terminal identification or internal circuit diagram of every relay printed on their body or their user manual. So, first, identify the magnetic coil terminals where the power supply is to be applied. Now, identify Normally Closed Contact terminals, then Normally Open Contact terminals.

Now connect the power supply to the coil terminals. Connect the NO terminals to the circuit where you are required to break the circuit in normal condition and close the circuit when the power supply is applied to the relay. Connect the NC terminals to the circuit where you are required to close the circuit in normal condition and break the circuit when the power supply is applied to the relay.

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Relay Wiring Diagram

Here, you can see a simple wiring diagram of a relay to understand its working principle in a circuit.

Now, let's discuss about this wiring diagram. 

It is the DC supply-operated 5-pin relay. Also, it is known as SPDT Relay. Pin no 1 is the positive pin of the magnetic coil(also known as coil terminal 1). Pin no 2 is the negative pin of the coil(also known as coil terminal 2). Although there is no polarity of the coil you can connect them in any manner. So we connected a DC power source across terminals 1 and 2 through an SPST switch. Using this switch we can turn on or turn off the power supply to the relay coil when we wish.

Terminal 3 is common for both NO and NC contacts. Terminal 5 is NO and Terminal 4 is NC. It means that in normal conditions terminal 3 is connected to terminal 4. When we apply the power supply to its coil, terminal 3 will be connected to terminal 5.

Here, you can see we connected two LEDs. The Red colour LED is connected to the NO terminal and the green colour LED is connected to the NC terminal. So, in normal conditions, the green colour LED will glow but when we apply the power supply to the relay by turning on the switch, the red colour LED will glow.

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