Programmable logic controller(PLC) is a digital electronic device with a microprocessor, It is a digital logic controller for automatic control, which can load control instructions into the memory for storage and operation at any time. Before the advent of programmable logic controllers, it was generally necessary to use hundreds of relays and counters to form an automation system with the same functions. But now, the simple programmable logic controller modules that have been programmed have basically replaced large-scale equipments. PLC are widely used in the current industrial control field. In the field of industrial control, the application of PLC control technology has become an indispensable member of the industry.