Introduction
As Europe's largest manufacturer of electronics and electrical equipment, Siemens plays a vital role in global industrial automation. Since the introduction of the SIMATIC brand in 1958, Siemens PLCs (Programmable Logic Controllers) have become core control devices in metallurgy, chemical engineering, and automotive manufacturing, thanks to their technological innovation and reliability. This article traces the development of Siemens PLCs and examines how they evolved from binary controllers to intelligent platforms for Industry 4.0.
1.Early Exploration: From Relays to Transistor Control (1958-1970s)
The birth of the SIMATIC brand marked the beginning of Siemens automation technology. In 1958, Siemens launched its first SIMATIC series product and released the SIMATIC G in 1959, which utilized transistor technology to replace traditional relays. This advance significantly enhanced the compactness and energy efficiency of control systems. The subsequent SIMATIC N series, introduced in the 1960s, incorporated silicon materials to further optimize device speed and stability, laying the groundwork for future digitization.
During this phase, PLCs were primarily hardware-based but demonstrated the potential to replace mechanical relays, offering preliminary solutions for industrial automation.
2. The Microprocessor Revolution: Breakthroughs with S3 and S5 Series (1970-1990s)
SIMATIC S3 (1975)
Siemens' first PLC product, the SIMATIC S3, was officially launched in 1975. It featured a binary controller design with a simple operating interface, primarily used for basic logic control tasks like production line switch control. Despite its limited functionality, the S3 series established a foundation for future products.
SIMATIC S5 (1979)
With the maturation of microprocessor technology, Siemens introduced the S5 series in 1979, effectively replacing the S3. This series was the first to incorporate microprocessors, allowing for more complex logical operations and introducing the STEP 5 programming tool, which could run on CP/M and MS-DOS systems. This transition marked a shift in PLCs from hardware to software programming. Typical models such as the S5-95U and S5-155U found widespread application in process control.
SIMATIC S5 PLC
Networked Early Stages
In the 1980s, the S5 series evolved into the U series models (e.g., S5-90U, S5-135U), improving modular design and enabling distributed I/O control, paving the way for industrial networking.
3. Digital Leap: The S7 Series and Totally Integrated Automation (1994-2000s)
The Birth of the SIMATIC S7 Series (1994)
In 1994, Siemens launched the groundbreaking S7 series, marking another revolutionary year for SIMATIC PLCs. Siemens introduced the first version of Profibus and integrated the industrial networking concept into the PLC realm. The SIMATIC S7 series includes three major models: S7-200, S7-300, and S7-400, targeting small, medium, and large control systems, respectively. Among these, the S7-300 became the most popular model, renowned for its wide range of CPU sizes suitable for nearly all applications.
Core Innovations:
- Modular Design: Allows flexible combinations, with the S7-300 offering 22 types of CPUs to meet different industrial scenarios.
- Windows Compatibility: The STEP 7 programming tool features a graphical interface, lowering the barriers for development.
- Network Communication: Integration of Profibus bus technology enables device-level networking.
The Concept of Totally Integrated Automation (TIA) (1996)
Siemens proposed the TIA (Totally Integrated Automation) concept to achieve seamless collaboration from design to production through a unified platform integrating PLCs, HMIs, and industrial software. The PCS7 process control system, released in 1996, combined the WinCC interface with Profibus networks, becoming a benchmark solution for process industries.
4. Intelligent Transformation: The Rise of S7-1200 and S7-1500 (2009-Present)
S7-1200 (2009)
The S7-1200, an upgrade to the S7-200, is characterized by its compact size and integrated Profinet interface, supporting distributed I/O expansion. Though aimed at the mid-to-low end of the market, its cost-effectiveness has made it a preferred choice for small automation systems.
S7-1500 (2012)
Established as the official successor to S7-300/400, the S7-1500 was designed for Industry 4.0 with several advantages:
- High-Performance Processor: Supports millisecond-level responses with a tenfold increase in code execution efficiency.
- Cloud Integration Capabilities: Built-in OPC UA protocol allows direct interfacing with edge computing and cloud platforms.
- Safety and Scalability: Offers redundant CPUs and fail-safe modules suitable for high-reliability applications.
Product Iteration and Market Strategy
Siemens announced the discontinuation of the S7-300 in 2023, with spare parts no longer available after 2033, urging users to migrate to the S7-1500.
5. Introduction to SIMATIC S7 Controllers
Having established a foundation in Siemens PLC history, let's review three leading SIMATIC PLC models on the market: S7-300, S7-1200, and S7-1500.
|
Feature |
S7-300 |
S7-1200 |
S7-1500 |
|
CPU Clock Speed |
48 MHz |
100 MHz |
400 MHz |
|
Profinet Support |
No |
Yes |
Yes (Advanced) |
S7-300 PLC Controller
The S7-300 PLC has become the most popular product among the first series of S7 offerings, helping establish Siemens as a leader in the automation industry. The S7-300 features a serial bus connector design and is suited for a broad range of complex process control tasks.
Compared to the S7-400, the S7-300 has fewer functionalities, memory, and I/O capabilities. However, its smaller footprint and cost-effectiveness afford it greater market prominence by balancing processing capability and expense.
Siemens offers 22 different versions of the S7-300 CPU, categorized into standard, compact, fail-safe, and technology types. Each type meets various requirements for different-sized factories. The compact CPUs maintain similar coverage to standard CPUs but are optimized for space-critical environments. Fail-safe CPUs integrate safety level control within a single device, while technology CPUs cater to advanced motion control applications.
The S7-300 PLC has been in the market for nearly thirty years, and Siemens has announced its official phase-out, with the industry migrating towards the more modern S7-1200 and S7-1500 PLCs.
S7-1200 PLC Controller
Launched to address several technical challenges presented by the S7-300, the S7-1200 offers smaller embedded I/O while maintaining modular scalability. However, it is not considered a formal successor to the S7-300, a role reserved for the S7-500. The S7-1200 serves as a transitional model, capable of fulfilling most functions of the S7-1500, with software easily transferable between the two models. Its compact dimensions, along with embedded I/O, make it an excellent choice for control panels. Many new applications have either transitioned to the S7-1200 system or rely on the distributed I/O blocks of the S7-1500.
S7-1500 PLC Controller
The S7-1500 series combines all the flexibility and scalability advantages of the S7-300 while anticipating the future of control automation technology. Many case studies around this series focus on Industry 4.0 and data analysis. The S7-1500 PLC is categorized into three types: standard, compact, and fail-safe, with applications similar to those of the S7-300.
The S7-1500 boasts significant improvements in processing speed, performance, and code length. Additionally, Profinet serves as the standard protocol used by S7-1500 controllers, equipped with protocols and networking capabilities suitable for edge and cloud computing.
Recent comparisons between the S7-1500 and S7-300 were conducted to select the best solutions for new automation projects. However, following the announcement of the S7-300's discontinuation, the S7-1500 has become the official solution, with many companies planning to transition to it.
6. Future Trends: Industry 4.0 and Sustainability
Siemens PLC innovations have consistently aligned with industrial demands. Currently, the S7-1500 supports artificial intelligence algorithms and digital twin technology, facilitating predictive maintenance and energy efficiency optimization. Furthermore, Siemens consolidates engineering software through the TIA Portal platform, enabling full lifecycle management from virtual debugging to actual production.
Conclusion
From the 1958 SIMATIC to the contemporary S7-1500, the history of Siemens PLC development represents an evolution of industrial automation technology. Through continuous technological innovation and market adaptation, Siemens has not only advanced the intelligent transformation of manufacturing but also led the way in global automation trends during the Industry 4.0 era. As cloud computing and AI continue to integrate, Siemens PLCs will remain central to industrial digitization.
