This module allows microcontrollers to control high-voltage devices (AC or DC) using opto-isolated relays. Each channel can be triggered by either HIGH or LOW logic, selectable via jumpers. This family includes the N25, 4N26, 4N27, 4N28. Functional operation of the device is not implied at these or any other conditions in excess of those given in the operational sec. We will learn three methods, first method is by connecting relay directly with the optocoupler output pins, second method is by using external PNP transistors, and third method is by using external NPN transistors. Any standard optocoupler such PC817, TIL111, or MCT2E can be used in the discussed. The 4N25 Optocoupler (also known as an optoisolator) is an electronic component that allows electrical signals to be transmitted between two isolated circuits using light.
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