Answer: Central processing unit (CPU), memory, input/output interface circuit (I/O interface circuit), power supply, communication interface.
Answer analysis:
PLC (Programmable Logic Controller) is an industrial automation control system, and its hardware structure is mainly composed of the following five basic components:
1. Central processing unit (CPU):
- The CPU is the core of the PLC, responsible for processing input signals, executing program instructions, controlling output signals, and providing monitoring and diagnostic functions.
- It consists of a controller and an arithmetic unit. The controller controls the various components of the entire computer to work in an orderly manner, while the arithmetic unit performs arithmetic and logical operations.
- The performance of the CPU directly affects the computing speed and processing power of the PLC.
2. Memory:
- The memory is used to store system management programs, monitoring programs and system internal data, as well as user programs and working data.
- The system memory includes RAM (random access memory) and ROM (read-only memory). RAM is used to store temporary data and program running results, and ROM is used to store fixed system programs and monitoring programs.
- The user memory includes the user program storage area and the working data storage area. The user program storage area stores the application programs compiled by the user, and the working data storage area is used to store data such as input and output status, timer/counter set values and elapsed values.
3. Input/output interface circuit (I/O interface circuit):
- The input interface circuit is used to collect external signals, such as sensor signals, button signals, switch signals, etc., and convert these signals into signals that can be processed by the internal circuit of the PLC.
- The output interface circuit converts the low-level signals inside the PLC into various signals required by the actuators (such as contactors, solenoid valves, etc.) in the industrial production site to control external devices.
4. Power supply:
- The power supply module provides a stable power supply for the PLC system to ensure the normal operation of all components of the system.
- It usually converts the external input AC power into a DC power supply that meets the working needs of the internal circuit of the PLC after rectification, filtering, voltage stabilization, etc.
5. Communication interface:
- The communication interface is a bridge for data exchange between the PLC and external devices (such as computers, instruments, etc.).
- It supports multiple communication protocols and interface standards (such as Ethernet, serial port, USB, etc.), enabling PLC to connect to other devices and transmit data.
These five parts together constitute the hardware system of PLC, realizing the control and monitoring of industrial automation equipment. In practical applications, PLC can also be configured with other auxiliary modules as needed, such as extended I/O modules, analog input and output modules, special function modules, etc., to expand its functions and scope of application.