Optocoupler Relay Driver with PC817

 

We all know that we can simply drive a relay with the help of transistor. But this method is not isolated. In many places we may require an isolation between the relay and the driving section.

In those places we use the optocouplers. Since these transfer the command using the light and have no electrical connection. Here, we are going to make a circuit of Optocoupler Relay Driver. Optocouplers are electronic components that are used to transfer electrical signals between two isolated circuits using light.

They prevent high voltages from affecting the circuit receiving the signal.

They contain an LED and a phototransistor and are manufactured in different packages. The simple optocoupler just has one LED and one phototransistor which we are using in this circuit.

The optocoupler relay driver circuits are used in various electronic projects. Here, we have made two types of circuits. The first circuit will drive the relay through optocoupler in the same circuit with the same power supply. Whereas the second circuit is completely isolated from the trigger source. The relay is powered with a separate circuit or power source.

Hardware Components

S.no Component Qty

1. Optocoupler PC817 1

2. Resistor 120R 1

3. Transistor 2N3904 1

4. Relay with 1N4007 diode 1

5. Connecting wires 1

6. Batteries 1

7. Breadboard 1

The working of both the circuits is simple, they are using only a few components. When a trigger signal is given the LED of the optocoupler lights up and this light energises the phototransistor inbuilt in the optocouplour. Once the phototransistor is activated it activates the relay driving transistor and hence the relay. They can operate at a wide supply voltage ranging from 3.6V to 12V DC.

The voltage of the relay should be the same as the operating voltage of this circuit.

Applications

Microcontrollers I/O switching

VoIP phones

Signal isolation

PC communications