Basic knowledge of PLC Introduction
Basic knowledge of PLC Introduction
In the field of automation and control, PLC is an important control equipment. Currently, there are more than 200 manufacturers to produce more than 300 varieties of PLC products, used in motor vehicles (23 percent), food processing (16.4%), chemical / pharmaceutical (14.6%), metal / mining (11.5%), pulp / made paper (11.3%) industries. In order to make you a beginner to more easily understand the PLC, basic knowledge of the development of the PLC, the basic structure, configuration, applications for an introduction, in order to help netizens.
A PLC course of development
In the industrial production process, a large number of switch order control, order of action in accordance with logical conditions, and controlling the motion of chain protection, and a large number of discrete data acquisition in accordance with the logical relationship. Traditionally, these functions are achieved by pneumatic or electrical control systems. U.S. GM (General Motors) in 1968 proposed to replace the following electrical control device requirements, the second year, the U.S. Digital developed a technology-based integrated circuits and electronic control devices, using procedural means for the first time used in electrical control, This is the first generation of programmable logic controller, called the Programmable Controller (PC).
In order to facilitate the development of the personal computer (referred to as PC) in order to reflect the features of the programmable controller programmable controller to be called the Programmable Logic Controller (PLC), and now, is still often the PLC referred to the PC. PLC definition. The International Electrotechnical Commission (IEC) of the PLC is defined as: programmable controller is a digital computing operation of electronic systems, specifically designed for applications in industrial environments. It uses a programmable memory, used to perform logical operations in its internal storage, sequential control, timing, counting and arithmetic and other operations instruction, and control all types of digital, analog input and output, machinery or production processes. Programmable controllers and related equipment, should be easy and industrial control systems form an integrated, easy to extend the principle of functional design. The 1980s to the mid-1990s, the PLC's fastest-growing period, the annual growth rate has been maintained at 30 to 40 percent. During this period, the PLC in the ability to handle analog and digital computing power, man-machine interface capabilities and network capabilities have been greatly improved, the PLC gradually entering the field of process control, in some applications to replace the DCS in a dominant position in the field of process control system
PLC has a versatile, easy to use and adapt to a wide range, high reliability, strong anti-jamming capability and simple programming. PLC in industrial automation and control, especially in the sequence control status in the foreseeable future, can not be replaced.
Second, the PLC composition of
PLC is divided into fixed and modular (modular) two points from the structure. Fixed PLC CPU board, I / O board, display panel, memory blocks, power, and these elements are combined into a non-removable as a whole. Modular PLC CPU module, I / O modules, memory, power supply modules, backplane or rack, these modules can be combined according to certain rules configuration.
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