Hi friends, I am writing this post to reduce the length of the video I am posting on youtube. This article works as a companion of my videos on the same topic. In this article let us learn how to use a 2 Channel Opto coupler relay with an Arduino Uno This is a Typical 2 Channel opto coupler relay available on Amazon India. At least that is where I bought one. This is a 5v relay. That means you need to give it a supply of 5v for it to operate. This relay needs supply on two pins.