2. PLC Programmable Logic Controller: As we all know, it is an electronic system of digital arithmetic operations, which is specially designed for applications in industrial environments. It uses a programmable memory in the internal stored program to perform logical operations, sequence control, timing, counting and arithmetic operations, and other user-oriented instructions, and controls various types of machinery through digital or analog input / output or production processes . . Programmable controller is a new type of universal automatic control equipment developed for industrial environment by combining computer technology and automation control technology. It seems to be an alternative to traditional relays. With the rapid development of microelectronics and computer technology, programmable controllers have more computer functions, which can not only implement logic control, but also have functions such as data processing, communication, and network. Because it can change the control process through software, and has the characteristics of small size, convenient assembly and maintenance, simple programming, high reliability, strong anti-interference ability, etc., it has been widely used in various fields of industrial control, which greatly promoted the mechatronics Into. deal with. The following PLC products are very popular in our market: Schneider’s Quantum, Premium, Momentum and other products; Rockwell (including AB) PLC products, currently SLC, Micro Logix, Control Logix and other products; Siemens currently, there are SIMATIC S7-400 / 300/200 series products. GE products; Japan’s Omron, Mitsubishi, Fuji, Panasonic and other companies.