The relay output is generally a strong power controlled by weak current. The output of the relay, the output current and voltage are written on the outer casing of the relay, that is, the weak current is used to control the strong current.
The relay output is generally a strong electric power controlled by weak current. This is the statement in circuit control.
In many automation equipment, the circuit ultimately needs to control some of the actuators (such as motors, electromagnets), the control of these components can be controlled by relays, triacs, transistors and other switching devices, so for the output of the circuit There are corresponding types of "relay output, bidirectional thyristor output, transistor output".
In fact, it is very simple. The ordinary relay is equivalent to a single-pole double-throw switch. There are three pins for controlling the external circuit. When the current is not controlled (the default state), the middle pin is connected to a left pin, and the middle pin is connected when the control current is applied. Passing the right pin, the relay is required to apply current to the electromagnet. Since this current is not small, the I/O port of the MCU alone is not enough for the relay to be connected. A drive should be added (power amplification, The relay is supplied with sufficient current), and then the MCU uses I/O port to control the drive, and then the drive circuit (driver chip such as UM2003) outputs enough current to make the relay pull in, which is the case.