What is an optocoupler?
An optocoupler or also known as an optoisolator is a switch that is activated by infrared light emitted by a diode led into a phototransistor or any other device capable of detecting infrared. When this light is interrupted or blocked by some object, the circuit opens acting as an open switch.


Parts of an optocoupler
The optocoupler is made up of 2 main elements, which are: an infrared led and an element capable of detecting infrared light, such as a phototransistor, a photostream, a MOSFET phototransistor, Photodarlington, etc.

optocoupler parts

How does it work
Despite being a somewhat complex device, its operation is easy to understand, since it only has a transmitter and a receiver. The emitter is an infrared led that sends a light beam to the receiver, which is normally a phototransistor, when this device picks up the signal it acts as a closed switch and when it is interrupted it acts as an open switch.

Optocoupler function

Optocoupler Types
Currently, there are different types that are distinguished, either by their output or by their type of use.

DIP encapsulation
This type is mainly used in electronic boards since its operation is based on activating and deactivating the circuit through voltage. They are mainly used to isolate possible interferences between two stages that operate at different voltages. such as the control stage with the power stage. There are different versions that are distinguished by their type of output.

Phototransistor: It is the most common of all and controls direct current at its output.
Fotodarlington: A darlington array that has two transistors together is added, which translates to a large current gain.
Fototriac: It is designed to control alternating current at its output.
Schmitt trigger: In this, its output is logical either 0 or 1.
AC input – transistor output: With this type, you can make a change from alternating current to direct current.
Optocoupler types

As sensor
This type is used as an optical sensor since the emitter and the receiver are linearly placed and when the infrared light is emitted it bounces off a surface which makes it return to the receiver when the receiver does not receive any signal, it means that there is no nearby object.

optocoupler sensor

As optical switch
This is practically the most attractive of all since it is used as an interface in logic circuits, it is usually used for the user to swipe a card or some object with little thickness. When you pass the object the signal is interrupted and this causes a change of state which indicates that your logic circuit can act either to activate or deactivate anything, such as a motor, a lock, a simple led, etc.