Under normal circumstances, the power input end of the PLC usually accepts an AC220V power supply to provide operating power for the PLC. At the same time, the output port of the PLC generally provides a DC24V power supply for powering the output devices connected to the PLC.
The following are some common situations and wiring methods for PLC input ports and output ports:
PLC input port:
- Switching signals: This includes buttons, travel switches, transfer switches, proximity switches, etc. The wiring is usually as follows: the switching signal line is connected to the input terminal of the PLC (usually represented as X0, X1, X2, etc.), and the other end is connected to the public port of the PLC (usually represented as the COM terminal).
- Analog signal: Analog signal usually comes from various sensors, such as pressure transmitters, liquid level transmitters, temperature sensors, etc. The wiring method will vary depending on the sensor type and operating range. Generally, factors such as signal type (voltage or current), signal range, and number of signal transmission lines (two-wire or three-wire) need to be considered.
PLC output port:
The output port of the PLC can adopt different output modes, such as relay output, transistor output or thyristor output, and the wiring method will depend on the type of PLC and output device used.
- Relay output: When the PLC uses relay output, the load capacity and relay type of the relay usually need to be considered. The output device is connected to the normally closed or normally open contact of the relay, and then the relay wire is connected to the corresponding output port of the PLC.
- Transistor output: A PLC can also use transistor output to control external devices. In this case, the output device is usually connected to the load side of the transistor, and the transistor lines are then connected to the corresponding output port of the PLC. Transistor outputs are often used to control low-power loads.
- Thyristor output: Some PLCs also provide thyristor output, which is usually used to control high-power loads such as motors. The wiring method will depend on the PLC model and equipment requirements.
Correct wiring is essential for the normal operation of the PLC. Before wiring, you should carefully read the manuals of the PLC and output devices to understand the correct wiring method and ensure that the electrical connections comply with safety standards and regulations.