Programmable Logic Controller (PLC) is a device that uses digital computer technology and specialized peripherals to achieve automated control of industrial processes. It plays a very important role in industrial production. In this paper, we will introduce the composition and characteristics of the programmable controller in detail.
First, the composition of the programmable controller
Central Processing Unit (Central Processing Unit, CPU): the core component of the programmable controller is the central processor, which is responsible for processing program logic, arithmetic operations and data transmission part, similar to the host CPU.
Memory (Memory): Memory includes the storage device of the programmable controller and the components for storing data. According to different functional requirements, memory can be divided into RAM, ROM, EPROM and other different types. Memory is used to store the program and data of the programmable controller, including the status of inputs and outputs, data values, etc.
Input/Output (I/O) Module: I/O module is the interface that inputs control signals and information from external devices into the programmable controller, or outputs control signals and information from the programmable controller to external devices. It usually includes an input module and an output module. The input module is used to detect external signals and convert them into digital signals for input to the central processor. The output module converts the digital signals output from the central processor into electrical signals to activate external actuating devices via electromagnetic relays, pneumatic devices, motors, and so on.
Bus: Bus is the communication interface for information transfer and sharing of resources (e.g. memory) between modules within the programmable controller. Bus mainly includes data bus, address bus and control bus.
Power supply module (Power Supply Module): power supply module for the programmable controller to provide the required power supply voltage and power. It usually includes regulated power supply, power conversion, over-voltage, over-current and short-circuit protection and other functions.
Communication module (Communication Module): Communication module is the programmable controller and the host computer or other external devices for data exchange, monitoring and control of the interface part. Communication module can be used in the form of serial communication port, Ethernet port, communication module.
Second, the characteristics of programmable controllers
Reliability: programmable controllers usually use modular design, each module is independent of each other, failure can be replaced locally, will not affect the work of the entire system.
Program flexibility: programmable controllers can be programmed to achieve different control functions. The program can be modified and expanded according to the actual demand, in order to adapt to the adjustment and change of the process.
Easy to use and maintain: The programming language of programmable controllers usually uses symbolic logic, which is easier to understand and operate than traditional wiring. At the same time, the standardized control software and programming tools for standardization, making the maintenance of the system easier.
Strong anti-interference ability: programmable controllers use digital signal processing technology, can effectively inhibit electromagnetic interference and other sources of interference on the system to improve system stability.
Strong expandability: programmable controller has good expandability, can be expanded by adding I / O modules, communication modules and other extended functions, as well as through the network for remote monitoring and control.
Reliable data storage: programmable controllers usually have non-volatile memory, so that the system can be restored to the state before the power outage in the event of a power outage or abnormal restart to avoid data loss and process interruption.
Third, the summary
Programmable controllers are an important part of modern industrial automation, with components such as a central processor, memory, I/O modules, buses, power supply modules and communication modules. Characteristics of programmable controllers include high reliability, program flexibility, ease of use and maintenance, high immunity to interference, high scalability and reliable data storage.
