The definition and development history of PLC

PLC is the abbreviation of the programmable logic controller, and PLC is an electronic computing control system. It is designed based on the principle of a simple storage program and convenient expansion provides instructions such as sequence/position control, timing counting, input/output control, etc., and is widely used in the field of industrial automation control. Next, let's take a look at the definition and development of PLC history. Here are some answers.

Here is the content list:

l What is the definition of PLC?

l What is the history of PLC development?

What is the definition of PLC?

Industrial Automation Products have the characteristics of strong versatility, convenient use, wide adaptability, high reliability, strong anti-interference ability, and simple programming. The International Electrotechnical Commission (IEC) defines PLC in its standard as a programmable logic controller is an electronic system for digital operations, designed for use in industrial environments. It uses a type of programmable memory for its internal storage program, executes user-oriented instructions such as logic operations, sequence control, timing, counting, and arithmetic operations, and controls various types of machinery through digital or analog input/output or production processes. The programmable logic controller and its related peripheral devices are designed according to the principle that it is easy to integrate with the industrial control system and expand its functions.

What is the history of PLC development?

The rise of programmable controllers is inseparable from the requirements of the development of modern industrial automation in the United States. A Wide Range of Quality Products at Great Prices originated in the 1960s. At that time, the General Motors Corporation of the United States, solved the problems of time-consuming modification of the circuit of the relay sequence control system and difficult maintenance and repairs to solve the adjustment of the factory production line. Before the appearance of programmable logic controllers, the general control, sequence control and safety interlock logic control in the automobile manufacturing industry had to rely entirely on numerous relays, timers, and specialized closed-loop controllers. They are bulky and have serious noise. Not only does the annual maintenance work consume a lot of manpower and material resources, but also the wiring maintenance of the relay-contactor system also has high requirements for the proficiency of maintenance personnel.

In response to these problems, General Motors of the United States invited public bids in 1968, requiring the design of a new system to replace the relay system, and proposed the famous "General Ten" bidding indicators. Subsequently, according to this idea, the American Digital Equipment Corporation (DEC) successfully developed the first PDP-14 controller in 1969, and used it on the automatic assembly line of automobiles and achieved success. Since the system was mainly used for sequential control and could only perform logic operations, it was named Programmable Logic Controller (PLC). The earliest PLC only had a simple logic on/off function, but compared with the traditional relay control method, it has the advantages of easy modification, installation, diagnosis, and less space.

In the early 1970s, PLC introduced microprocessor technology, enabling PLC to have arithmetic operation functions and multi-bit digital signal output/input functions, and can directly write programs with ladder diagram symbols. The use of this new technology has produced huge repercussions in the industry. Japan introduced this technology from the United States in 1971 and quickly developed its own DCS-8 programmable logic controller. Germany and France also had their technology from 1973 to 1974. China successfully developed its first programmable logic controller in 1977, but the microprocessor core used was MC14500. In the mid-1970s, PLC functions added technologies such as long-distance communication, analog output and input, and NC servo control. After the 1980s, High performers’ high-speed communication network functions were introduced, and some special output/input interfaces, man-machine interfaces, high-function function instructions, data collection and analysis capabilities, and other functions were added. The function of PLC has long been beyond the operation function of digital logic, so in recent years PLC is often referred to as Programmable Controller.

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