An Optocoupler also known as Photocoupler or Optical Isolator is a component that transfers electrical signals between two isolated circuits using light. It physically and electrically separates a low-voltage control circuit (like a microcontroller) from a high-voltage or noisy power circuit (like a motor or AC mains). It is basically a solid-state relay that optically interconnects two electrically isolated circuits.

In this tutorial, I am going to talk about the PC817 Optocoupler which is one of the most common and inexpensive 4-pin optocouplers.

Video: https://www.youtube.com/watch?v=Rj9H0beMQq8
Blog: https://diyfactory007.blogspot.com/2025/12/blog-post.html