In modern industrial automation, the “PLC (Programmable Logic Controller)” is virtually ubiquitous. From production lines and packaging equipment to water treatment and building automation, it serves as the system's brain, determining the stability and efficiency of the entire automated process.

I. Core Functions of PLCs

At its core, a PLC is an industrial-grade computing and control unit.

It acquires field signals, executes logical judgments, and controls output devices—serving as the critical link in achieving automated control.Compared to traditional relay systems, PLCs offer superior interference resistance, high reliability, and flexible programming. They can be expanded and interconnected to meet diverse requirements.

II. Leading Brands and Functional Differences

1· Siemens

Renowned for stability and system integrity, the S7 series seamlessly integrates with HMIs, frequency converters, and industrial Ethernet.

Advantages: High compatibility, powerful engineering software;

Disadvantages: Higher cost, steeper learning curve for beginners.

Case Study: Yingke Wastewater Treatment Plant Automation Upgrade (Siemens S7-1500)

The project employed S7-1500 series PLCs to automate pump station start/stop, liquid level monitoring, and remote supervision. Field devices were connected via Profinet network, with real-time data transmission to the central control room enabling unmanned operation.

Results: Manual inspection frequency reduced by 60%, energy consumption cut by approximately 15%.

2. Mitsubishi Electric

FX and Q series widely adopted in packaging, machine tools, and assembly lines.

Advantages: Fast response speed, moderate pricing;

Disadvantages: Limited number of expansion modules.

Case Study: Guangyi Food Factory Packaging Line (Mitsubishi FX5U)The FX5U series PLC controls conveyor belts, weighing systems, and sealing machines. Combined with high-speed I/O modules, the system precisely synchronizes process actions, reducing errors.

Results: 20% increase in packaging efficiency, 30% reduction in failure rate.

3·Schneider Electric

The Modicon series is renowned for its open communication and modular design.

Advantages: Supports multiple industrial buses, easy integration;

Disadvantages: Relatively weak software ecosystem.

Case Study: Chuangfeng Intelligent Building Lighting System (Schneider Modicon M221 + KNX)

Integrating PLC with KNX bus enables centralized control and zoned management of lighting, HVAC, and blinds. Users remotely operate systems via touch panels or mobile apps, balancing energy efficiency and comfort.

Result: Overall building electricity consumption reduced by approximately 18%.

IV. How to Select the Right PLC?

There is no “best PLC,” only the PLC best suited to project requirements.Consider the following when selecting:

1·Control scale and I/O quantity

2·Communication needs (Ethernet/IP, Profinet, etc.)

3·Software ecosystem and after-sales support

4·Cost and scalability

Conclusion:

PLCs serve as the nerve center of industrial automation, connecting not only machinery but also efficiency, data, and intelligence.

With the deep integration of AI and IoT, PLCs are evolving from “controllers” into the “brains of smart manufacturing.” Enterprises that master PLC application capabilities will gain a competitive edge in the automation wave.