OPTOCOUPLER 817 SINGLE

Optocoupler PC817 used here has an LED and a phototransistor in it. So when this circuit is powered the LED will receive the voltage and light up. This light will turn the phototransistor on and the optocoupler switches on. The output coming from this optocoupler will not activate the relay directly. that’s why we have used a 2N3904 NPN transistor at the output of this optocoupler. This transistor will receive current at its base and will be activated which drives the relay.

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

Applications and Uses

• Microcontrollers I/O switching
• VoIP phones
• Signal isolation
• PC communications