Plc modules to today, has formed a large, medium and small series products of all sizes. Can be used for all sizes of industrial control applications. In addition to the logic processing functions, most modern PLC has a complete data computing capability, can be used for a variety of digital control. In recent years, large numbers of PLC functional unit that infiltrated into the position PLC control, temperature control, CNC and other industrial control. And Development Plc modules plus enhanced communication capabilities of human-machine interface communication module plc technology, the use of PLC control system composed of a variety becomes very easy. Easy to use, well engineering and technical personnel welcome PLC as general industrial control computer, industrial and mining-oriented industrial equipment. It is easy interface, the programming language is easy for engineering and technical personnel to accept. Ladder language graphic symbols and expression and relay circuit is very close, with only a small switch on the PLC logic control instructions can easily achieve the function relay circuit. Is not familiar with the electronic circuits, computers do not understand the principles and assembly language people use computers in industrial control to open the door. System design, construction workload is small, easy to maintain, easy to transform PLC logic instead of using store-wired logic, greatly reducing the external control equipment wiring, the control system design and construction period is much shorter, but also becomes easier to maintain. More important is to change the program of the same device high-speed counter plc has been possible to change the production process. It is suitable for many varieties, small batch production applications. Small size, light weight, low power consumption In ultra-small Plc modules, for example, recently produced varieties bottom size less than 100mm, weighs less than 150g, power consumption is only a few watts. Due to small size it is easy to mount inside machinery, mechanical and electrical integration is to achieve the ideal control equipment.
In the industrial production process, a lot of switching sequence control, which in accordance with the conditions of the order to move a logical and controlled chain protection plc controller manufacturers action in accordance with the logic of relations, and a large number of discrete data collection. Traditionally, these functions are controlled by pneumatic or electrical system to achieve. 1968 American GM (General Motors) companies to replace the electrical control device, following the requirements of the second year, the United States developed a digital control device company based integrated circuits and electronic technology, for the first time using procedural means used in electrical plc digital input output io module control, which is the first generation of high speed counter plc, said the Programmable Controller (PC). After a personal computer (referred to as PC) to develop, in order to facilitate, but also to reflect the high speed counter plc's features, programmable logic controller named Programmable Logic Controller (PLC), and now, still often referred PLC PC.
In the late 1970s, the programmable controller into the practical stage of development, the introduction of computer technology has been fully programmable plc programmable intelligent controller controller, its function occurred leap. Higher operation speed, ultra-small size, more reliable industrial anti-jamming design, analog operation, PID function and high cost laid it in modern industry. The early 1980s, the programmable controller in the advanced industrial countries has been widely used. Features programmable controller is a large-scale plc analog input output io module development of this period, high-speed, high-performance, product serialization. Another feature of this stage is the national production of programmable controllers increasing world production rising. This marks the programmable controller has entered a mature stage.
There are many definitions PLC. International Electrotechnical Commission (IEC) is the definition of the PLC: Programmable Logic Controller is a digital electronic computing operating plc programmable intelligent controller system, designed for applications in industrial environments. It uses a programmable memory, used in its internal storage to perform logical, sequential control, timing, counting and arithmetic operations such as operating instructions, and through digital and analog inputs and outputs, control types machinery or production processes. Programmable logic controller and related equipment, all with industrial control systems should be easy to form a whole, to expand the principles of the design of its functions. The mid-1980s to the 1990s, is the fastest growing PLC period, the annual growth rate has been maintained at 30 to 40 percent. During this plc analog input output io module period, PLC capability in handling analog and digital computing power, man-machine interface capabilities and network capabilities have been greatly improved, PLC gradually entering the field of process control, in some applications in the field of process control to replace the dominant DCS systems. PLC has the versatility, ease of use, wide adaptation, can be * high anti-jamming capability, programming and simple. PLC in the industrial automation and control especially in order to control the position, in the foreseeable future, can not be replaced.