What are PLC？

The concept of PLC
The Chinese meaning of PLC (Programmable Logic Controller, PLC: editable logic controller.

Before the PLC appeared, the traditional circuit looked like this (as shown below).

By inching the SB2 button to close the normally open contact, the KM1 AC contactor coil is energized, the KM1 main contact of the AC contactor is closed, and the three-phase asynchronous motor is powered forward. The SB3 normally open contact is to control the reverse rotation of the motor.

It can be seen from the circuit diagram that the function of the traditional circuit is fixed and the contacts are limited. If you want to modify the function of the line, it will affect the whole body, and the corresponding line must be disconnected. If you need to control many motors, you need to connect many corresponding lines. And when a fault occurs, it is very troublesome to check the line on site.

After using the PLC, it is very simple and easy to connect these components to the PLC. (As shown below)

You only need to connect suitable components such as switch buttons to the PLC input, and loads such as indicator lights to the output.

Then write the program shown in the figure below on the programming software, and write the program to the PLC to run.

By pressing the switch button connected to the outside of the PLC, through the PLC scanning program, the X000 normally open contact is closed, and the Y000 coil is controlled to conduct, and the corresponding Y point outside the PLC can output and control the load.

Advantages of PLC:

If the key X00 is pressed externally to control Y001, only the program needs to be modified. Re-write to the PLC to run, without disconnecting the wires, press X00 and press the button to control asynchronous loading.

Some programs can be written in programming software.

And there is no limit to the number of normally open and normally closed contacts used in the programming software.

It is also possible to monitor the actual situation through programming software monitoring program, fast live broadcast, and troubleshooting is also very easy.