PLC has many features, such as high performance, compact structure, powerful function, and cost-effective. It can be widely used in textile and chemical fiber, machine tools, cables, food and beverage, packaging, steel, construction machinery, air conditioning, elevators, printing and other machinery manufacturing industry.The controller refers to the main command installation of changing the wiring of the main circuit or the control circuit and changing the resistance value in the circuit to control the starting, speed regulation, braking and reverse of the motor in a predetermined sequence. It consists of a program counter, an instruction register, an instruction decoding encoder, a step generator, and an operation controller. It is a "decision making body" that issues orders, that is, it coordinates and directs the operation of the entire computer system. Commonly used controllers in automation factories are PLCs, industrial computers, etc. PLC uses a type of memory for its internal storage programs, performs logical operations, sequence control, timing, counting and arithmetic operations, and other user-oriented instructions, and controls various types of machinery or through digital or analog input / output production process.