The Programmable Logic Controller (PLC) is a digital electronic device with a microprocessor. It is a digital logic controller used for automatic control and can load control instructions into memory for storage and execution at any time. Programmable controller consists of internal CPU, instruction and data memory, input and output unit, power module, digital analog unit modular combination.
Widely used in the field of industrial control. Prior to the advent of programmable logic controllers, it was common to use hundreds of relays and counters to form an automated system with the same function. Now, simple programmable logic controller modules have basically replaced these large devices. The system program of the programmable logic controller has been initialized before leaving the factory. Users can edit the corresponding user program according to their own needs to meet different requirements of automatic production.
The original programmable logic controller only had the function of circuit logic control, so it was named programmable logic controller. Later, with the continuous development, these computer modules with simple functions have been equipped with many functions, including logic control, timing control, analog control, multi-machine communication and so on. The name was also changed to Programmable Controller, but because it was also short for PC and Personal Computer, and because of years of habitual use, the term was often used. The abbreviation PLC is still used in the term.