What is optocoupler?

The optocoupler is the electronics component, it looks like a "IC" but its work as a transistor, but optocoupler is some different from transistor. 

The optocoupler is used to connect two isolated circuits, means it can connect two isolate circuits together without any electrical connection, the two circuits can communicate each other by optocoupler.

Such as transformer that it’s not has any electrical connection in two windings, but it connected by magnetic field, same like this optocoupler connected two circuit by lighting signal.

How to works optocoupler?

Like a transistor needs an electrical signal, and we apply signal on transistor's pin then it perform work of switching, same like optocoupler's transistor needs lighting signal then it perform work, and this lighting signal give LED to it, this LED has inside it.

The optocoupler has inside a LED and a photo transistor, it has only these two main workings parts, when voltage is supplied to LED's pins then it give     lighting signal to photo transistor, then photo transistor give the signal.

If voltage disconnected from LED so its photo transistor remain in open circuit condition, and this is normal condition of the optocoupler.

It’s internal some like this

How to use optocoupler

The typically optocoupler has Four pins

1-  Anode
2- Cathode
3- Emitter
4- Collector

The Anode and Cathode is the pins of LED, means these two pins used for input signal, and Emitter and Collector is the pins of photo transistor, and this two pins used for output signal.

When the anode pin used for the positive input current, and cathode used for negative input current, and Emitter pin used for input signal which signal we required in as a output signal.

Connection of optocoupler

How to check optocoupler by multi meter

First set multi meter at diode range or continuity range, then positive probe of meter connect to optocoupler's Anode pin and negative probe connect to Cathode pin and see the reading on multi meter, reading must come near about 1200 or 1100, if value below from this reading it means optocoupler is burnt.

After it, apply the left probe to right side, and right probe to left side, then value should not come, if value come then it means coupler is burnt

After done this , connect the multi meter probe to the emitter and collector, connect the first negative probe to the emitter and the positive pin to the collector, and vice versa, so value should come at one side not both sides, if value come only one side that means optocoupler is good, otherwise it's burned.

Opto coupler pins 

We can easily identify Opto coupler pins by its dot, in any opto has this dot symbol which denote to anode pin.

 

Uses of optocoupler

The optocoupler used in SMPS or Power supply and transmit analog or digital information between to circuit and etc.

It used in SMPS for for voltage maintenance it forward signal from output side to input side for voltage variation.

How to use optocoupler as a switch

The optocoupler can used as switch but it can't directly switching to any heavy appliances, because its collector ampacity is very low, means it can't support flow of high current, so if we want that heavy appliance switch by optocoupler then we require a relay.

We provide low electronics signal to optocoupler and optocoupler give signal to realy, thus relay can easily switching to any equipment.