An optocoupler, also known as an opto-isolator or photocoupler, transfers electrical signals between circuits using light. This unique design ensures that the two circuits remain electrically isolated. Optocouplers are very useful when you need to isolate different sections of a circuit, for example in power. In choosing appropriate values for R1, the value for the current limiting resistor is set to produce the correct forward current (I F) through the infrared LED in the optocoupler. Often in MCU boards I see optocouplers even when the power supply is the same on both sides.
