1. Overview of PLC Technology
PLC (Programmable Logic Controller) is the core device in the field of electrical engineering and automation control. Since its emergence in the 1970s, PLC has rapidly become the standard equipment for industrial automation control due to its high reliability, flexibility, ease of programming, and maintenance. PLC can perform complex tasks such as logic control, timing control, and counting control. Additionally, it can achieve advanced functions like analog control and motion control by expanding with functional modules, making it an indispensable part of modern industrial automation.
2. Principle of PLC Technology
PLC (Programmable Logic Controller) technology is a widely used control system in industrial automation. Its basic principle is to use a digital electronic computer for specific industrial control applications. A PLC system consists of an input module, central processing unit (CPU), output module, and programming device.
The input module receives external input signals from sensors, switches, and other devices, such as button states and sensor detection values. The CPU executes pre-written control programs and processes the input signals based on program logic to make decisions. The output module sends the processed signals to actuators like electric actuators or solenoid valves to control the operation of the equipment.
PLC programming languages mainly include Ladder Diagram (LD), Function Block Diagram (FBD), Instruction List (IL), and Structured Text (ST). Ladder Diagram is the most commonly used programming language, similar to the circuit diagram in electrical control systems, making it easy to understand and write.
PLC operates in a cyclical scanning process: First, the input module scans and reads the states of all input signals; then, the CPU performs data processing and decision-making according to the program logic; finally, the output module updates the output to control the corresponding actuators based on the program’s results.
PLC technology is characterized by high reliability, strong flexibility, and wide adaptability, and it is widely applied in industrial control systems, such as in manufacturing, energy management, and transportation, providing effective solutions for automated production.
3. Working Modes and Process
PLC’s working modes typically include Stop Mode, Run Mode, and Programming Mode. In Stop Mode, the PLC does not perform any input/output operations, allowing only programming and debugging. In Run Mode, the PLC processes input signals according to the internal program and outputs control signals. The Programming Mode allows users to write, modify, and debug programs through programming software.
The PLC work process consists of three main stages: input sampling, user program execution, and output refreshing. During the input sampling stage, the PLC scans the status of all input ports and stores it in the internal input image register. In the user program execution stage, the CPU performs logical operations and processing according to the program instructions and stores the results in the internal output image register. In the output refreshing stage, the PLC outputs the states from the output image register to the corresponding output ports to control external devices.
4. PLC System Components
The PLC system is composed of hardware and software. The hardware includes the CPU module, I/O modules, power supply module, communication module, memory, etc. The software includes system software and application software. System software is essential for the normal operation of the PLC and includes the operating system, programming language interpreter, etc. Application software is the user-written program based on specific control needs to realize particular control functions, as shown in the diagram of the PLC system composition.
5. Features of PLC Technology
As a product of the modern era, PLC technology has unique features. First, it takes into account the resolution approval of repeater stations and the design practices for internal flow. These practices are defined as ideal internal flow practices. The projects must consider their availability. Second, the solution is simple and clear. The PLC process not only improves employee performance but also increases productivity and quality. This is one of the most popular features of PLC technology in other companies. Fourth, PLC systems are easy to maintain. Their self-diagnostic functions greatly reduce the likelihood of faults and ensure high reliability and resistance to interference in system operations. Fifth, PLC can be integrated into programming languages and translated into device languages, eliminating the need to learn different technical languages in disciplines like electrical engineering and automation. This is because PLC technology and automation installation processes are simple and widely applicable, reducing the difficulty of obtaining PLC technology.
PLC technology is highly integrated, and its functions have been reduced, which helps reduce energy consumption within sustainable concept structures. PLC interfaces using universal PLC technology must meet national standards. Optical transmission chains increase interference but also reduce external signal disturbances, ensuring the stability and reliability of data transmission. Moreover, PLC technology includes a filtering circuit to provide optical protection against electronic interference, promoting the overall safety and stability of the system.
6. Application Value of PLC Technology
PLC technology has numerous advantages in electronic automation control. The integration of PLC technology with relay technology makes its application in the Internet of Things possible and allows electric motor control to comply with conventional technical standards. PLC technology is valuable because it can influence industrial production and promote economic development. PLC plays an essential role in modern enterprise equipment and project management, optimizing the efficiency of electronic control systems and making full use of the benefits of facilities and related technologies.
PLC technology is highly controllable and supports translation of control levels into general languages. Based on an understanding of language structures and patterns, it also ensures the correct control methods are applied, enhancing the effectiveness of applications. Additionally, PLC technology has an automatic translation feature, ensuring usability for future users. Due to PLC’s advantage in collaborative interpretation, it is crucial to clarify the system structure when managing technical projects to reduce complexity and improve work efficiency. By using PLC technology, it can integrate with international communication standards, provide security for the replacement of PLC technologies from different manufacturers, and improve processing efficiency and performance levels. In the process, system performance is enhanced, and the management features of PLC technology continue to evolve.
During this process, the ability to prevent system faults is consistently optimized, ensuring the reliability of electrical and mechanical control. Thanks to its powerful anti-interference capabilities, PLC technology also includes detection and self-understanding functions, such as the development of additional tools within the PLC system. This facilitates timely fault detection by operators, leading to prompt troubleshooting.