What is a PLC ?
A PLC integrates computer technology, automatic control technology, and communication technology. It uses user-oriented "natural language" programming for control, making it suitable for industrial environments. It is simple to understand, easy to operate, and highly reliable industrial control equipment. A PLC is a general-purpose automatic control device with a microprocessor at its core, developed from relay sequential control.
Technicians would say: PLC is an advanced control technology.
Salespeople might say: PLCs are money and market; they can sell PLCs directly even without understanding the technology.
The owner of an automation company might say: PLC is a profitable industrial control product.
In fact, PLC is just about time.
The advent of PLCs has reduced the production cycle of automobile production lines from 6-9 months to 6-9 weeks, and the same applies to steel, petrochemical, and other industries. The establishment of automated control systems has significantly shortened production cycles and increased production volume. What does this saved time mean for businesses? It means profit. Wireless PLCs further improve time efficiency.
PLC products themselves do not create any value; their powerful value is only revealed when they are meticulously crafted by engineers and applied in production. It is precisely this time-saving value created by PLCs that has led to their mature and widespread application across various industries, from FA (Factory Automation) to PA (Power Automation). This is due to their stability, low cost, and increasingly broad functional extensibility.
Basic functions of a PLC
It includes logic control, timing control, counting control, stepping control, data processing, loop control, communication networking, monitoring, power outage memory, and fault diagnosis.
The difference between a microcontroller and a PLC
Essentially, a PLC is a pre-built microcontroller system. Furthermore:
1. A PLC is a relatively mature control system composed of a single-chip microcomputer. It is a mature and stable single-chip application system product that has been debugged and is highly versatile.
2. Microcontrollers can be used to form various application systems, making them more versatile. In contrast, a "microcontroller" is simply an integrated circuit that must be combined with other components and software to form a system.
3. From a project usage perspective, using a PLC for a single project or a few projects with infrequent repetitions is quick and convenient. It offers high success rates and reliability, but at a higher cost.
4. For large-scale supporting projects, the use of microcontroller systems has the advantages of low cost and high efficiency, but considerable R&D strength and industry experience are required to ensure system stability.
What should a complete beginner learn to learn PLC?
First, you need to understand electrical engineering knowledge, how electrical appliances are controlled, and various actuators. Then, you need to understand how PLCs work, their input and output circuits, and finally, the corresponding processes.
1. When learning PLC, the first step is to choose which manufacturer's PLC to learn from. Japanese PLCs have high internal software integration and are easy to use. In the early days, OMRON and Mitsubishi were more widely used, but now, due to trade and international cooperation, Siemens and Rockwell PLCs are more commonly used.
2. PLC is not a single programming technology; it's a systematic and professional course. A PLC can be broadly considered a highly reliable PC with an embedded operating system. First, you need a deep understanding of PLC programming languages such as ladder diagrams. Reaching this level allows you to understand pre-written programs and design programs for engineering needs. This industry also requires the application of VB and VC++ for serial communication and distributed control systems. Some large programs also require knowledge of databases.
3. PLC is a discipline that emphasizes application. Therefore, more practical experience is essential. For example, every time you go to the site for debugging, call up the program on-site to examine it, understand its structure, and see how it differs from other programs and its characteristics.
Recommended books for PLC beginners with no prior knowledge: "PLC Programming Theory, Algorithms and Techniques (2nd Edition)", "PLC Programming and Troubleshooting", "Quick Learning and Application of Mitsubishi PLC Programming", "Quick Introduction to Siemens S7-200 Series PLC Programming Instructions and Ladder Diagrams", and "PLC Programming for CNC Machine Tools".
