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Description

The PC817 Optocoupler is used to provide electrical isolation of a signal between 2 circuits by using an optical bridge.Optocouplers, also called Photocouplers or Opto-isolators consist of a combination of an infrared LED and a phototransistor in a single package that is used to optically couple an electrical signal through the device without using an electrical connection. The device is uni-directional and can only pass a signal in one direction. Optocouplers are used to provide electrical isolation between two points in a circuit. Most often, they are used in a digital circuit to provide electrical isolation between a uC and a high energy output circuit such as a motor or to provide an additional layer of protection when using something like a relay to control a high energy device. They work by blocking any electrical spikes that might otherwise find their way back down the line to the uC. Inserting one of these in line with a uC pin will help to protect that pin, but in order to fully isolate two parts of a circuit, it also requires that separate power systems be used on the two sides of the circuit so that there are no electrical sneak paths back through the power system. This is typically over-kill for most hobby applications, but something to consider when full isolation is desired. Internally, the device has an IR LED on one side and a phototransistor on the other side of the device. Driving the LED causes the base of the phototransistor to also be driven, thus turning on the phototransistor.

Characteristics