Isolation devices commonly used in electrical applications include optocouplers, relays, and transformers.
The optocoupler is a flow-controlled component, which uses light as the medium to transmit signals: electricity → light → electricity, the input end is a light-emitting diode, and the output end is a photosensitive semiconductor. The core application of optocouplers is isolation and is often used in systems where there is no common ground between the input and output. Therefore, the withstand voltage between input and output can reach thousands of volts.
Many communication modules are also isolated by optocouplers, which makes it easier to realize the connection between various systems, and there is no need to consider whether it is a common ground.
Optocoupler control relay (low power), in order to enable the optocoupler to effectively drive the relay, the impedance of the output terminal should be small, so the current of the input terminal should be large