What is a programmable logic controller? The programmable logic controller is a kind of digital operation and operation electronic system specially designed for application in the industrial environment. It uses a programmable memory to store instructions for performing logic operations, sequence control, timing, counting, and arithmetic operations, and control various types of mechanical equipment or production through digital or analog input and output. process.
A programmable logic controller is essentially a computer dedicated to industrial control. Its hardware structure is basically the same as that of a microcomputer. The basic composition is shown in the figure below, and the basic composition is described in detail as follows:
Power supply
The power supply is used to convert alternating current into the direct current required by the PLC. At present, most PLCs use switch-mode stabilized power supplies.
Central Processing Unit (CPU)
The central processing unit is the control center of the PLC and the core component of the PLC. Its performance determines the performance of the PLC.
The central processing unit is composed of a controller, arithmetic unit, and registers. These circuits are all concentrated on a chip and are connected to the input/output interface circuit of the memory through an address bus and a control bus. The role of the central processing unit is to process and run user programs, perform logical and mathematical operations, and control the entire system to coordinate.
Memory
Memory is a semiconductor circuit with memory function, and its function is to store system programs, user programs, logic variables, and other information. Among them, the system program is the program that controls the PLC to realize various functions. It is written by the PLC manufacturer and solidified in the read-only memory (ROM), which cannot be accessed by the user.
Input unit
The input unit is the input interface that connects the PLC to the controlled device and is the bridge for the signal to enter the PLC. Its function is to receive the signal from the master component and the detection component. The input types are DC input, AC input, AC, and DC input.
Output unit
The output unit is also the connecting part between the PLC and the controlled device. Its function is to transmit the output signal of the PLC to the controlled device, that is, convert the weak current signal sent by the central processing unit into a level signal to drive the executive element of the controlled device. The output types include relay output, transistor output, and thyristor output.
In addition to the above parts, PLC also has various external devices of different models, its function is to help to program, realize monitoring and network communication, the commonly used external devices are programmers, printers, cassette tape recorders, computers. and many more. If you want to learn more about electronic components, please visit Jotrin. Here are the latest and hardest electronic components to find.
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