How does PLC control the opening and closing of contactor?

The output signal of PLC and the output COM connect the power supply and the contactor coil into a loop, and whether the contactor coil is electrified or not is controlled by the switch output. Generally, an intermediate relay transition (PLC output -DC24V-AC 220V) is added.

PLC: A programmable memory used to store programs and execute user-oriented instructions such as logic operation, sequence control, timing, counting and arithmetic operation, and input them through digital or analog input; #47; Output controls various types of machines or production processes.

The PLC control relay is connected to the control contactor: the output of PLC is connected to the coil of relay. So as to control the on-off time, and then use the relay to control the motor, solenoid valve and so on.

Extended data:

When designing the external wiring diagram and ladder diagram of PLC according to the relay circuit diagram, we should pay attention to the following problems:

(1) shall conform to the syntax of ladder diagram language. Because of the different working principles, ladder diagram can not completely copy some processing methods of relay circuit. For example, in a relay circuit, the contacts can be placed on both sides of the coil, but in a ladder diagram, the coil must be placed on the far right side of the circuit.

(2) Proper separation of some circuits in relay circuit diagram. When designing the schematic diagram of relay circuit, a basic principle is to minimize the number of contacts used in the diagram, because this means saving costs, but it often makes the control circuits of some coils intertwined.

(3) When designing a ladder diagram, the first problem is that the design idea should be clear, and the designed ladder diagram should be easy to read and understand. We don't particularly care whether to use more contacts, because it won't increase the cost of hardware, but it takes a little more time to input programs.

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