Top 7 IEC 61131-3 Programming Languages and Their Uses

Did you know that in today’s modern factories, robots equipped with Programmable Logic Controllers (PLCs) can perform intricate tasks with precision, speed, and reliability, revolutionizing industrial production?

PLCs are the brains behind the operation, controlling machinery and processes to ensure smooth and efficient operations. They are pivotal in industrial automation, from manufacturing to energy management systems. However, programming these controllers can be a daunting task.

Enter IEC 61131-3, a standardized language designed for PLC programming. Its importance lies in providing a common framework for programming, making it easier for engineers and technicians to understand and maintain automation systems across different platforms and vendors.

In this blog, we’ll dive deep into IEC 61131-3 programming languages. We’ll simplify the complexities, offer practical insights, and provide step-by-step tutorials to help you master PLC programming with ease. Whether you’re a beginner or an experienced professional, join us on this journey to unlock the full potential of industrial automation through IEC 61131-3.

What is IEC 61131-3 Programming Language?

IEC 61131-3 Programming Language is a set of standardized programming languages used in industrial automation for programming Programmable Logic Controllers (PLCs). 

These languages include Instruction List (IL), Structured Text (ST), Function Block Diagram (FBD), Sequential Function Chart (SFC), and Ladder Diagram (LD). 

Each language has its syntax and features tailored for specific programming tasks, offering flexibility and versatility in PLC programming. 

IEC 61131-3 ensures interoperability and ease of maintenance across different PLC platforms and vendors. It has become the de facto standard in the industry, enabling engineers and technicians to develop, troubleshoot, and maintain automation systems efficiently.

Major Features of IEC 61131-3 Programming Languages

IEC 61131-3 Programming Languages offer a range of features tailored for industrial automation:

1. Standardization

IEC 61131-3 provides a standardized set of programming languages, ensuring compatibility and interoperability across different PLC platforms and vendors.

2. Flexibility

The suite of languages, including Instruction List (IL), Structured Text (ST), Function Block Diagram (FBD), Sequential Function Chart (SFC), and Ladder Diagram (LD), offers flexibility in choosing the most suitable language for specific programming tasks and preferences.

3. Modularity

Languages like FBD and LD allow for modular programming by breaking down complex processes into manageable functional blocks, enhancing code reusability and maintainability.

4. Ease of Use

With intuitive graphical and text-based syntax, IEC 61131-3 languages are accessible to both novice and experienced programmers, facilitating efficient development and troubleshooting of automation systems.

5. Debugging Support

Built-in debugging features such as online monitoring, breakpoints, and variable inspection streamline the debugging process, enabling rapid identification and resolution of errors in PLC programs.

Best IEC 61131-3 Programming Languages and Their Uses

IEC 61131-3 is a standard for programming languages used in programmable logic controllers (PLCs) in industrial automation. It defines several programming languages that can be used for different purposes in PLC programming.

1. Instruction List (IL)

IL is a low-level, text-based language in IEC 61131-3, resembling assembly language. It consists of simple instructions represented by mnemonic codes, making it efficient for basic control tasks. While less intuitive than graphical languages, IL offers precise control and is commonly used for performance-critical applications in industrial automation.

Uses of This Programming Language

• Basic control tasks such as on/off control.
• Direct manipulation of memory and registers.
• Simple arithmetic and logical operations.
• Sequencing and branching operations.
• Fast execution of performance-critical tasks.

2. Structured Text (ST)

ST is a high-level, text-based language similar to programming languages like Pascal or C. It allows for structured programming with conditional statements, loops, and user-defined functions, facilitating complex algorithm implementation in PLC programs. ST is widely used for its readability, flexibility, and support for mathematical operations.

Uses of This Programming Language

• Complex mathematical algorithms and calculations.
• Conditional statements and loops for decision-making.
• Text manipulation and string handling.
• User-defined functions and libraries for code reusability.
• Communication protocols and data handling operations.

3. Function Block Diagram (FBD)

FBD is a graphical language in IEC 61131-3, representing control logic using interconnected function blocks. Each block performs specific functions or operations, and connections between blocks define data flow. FBD offers visual clarity and modularity, making it suitable for both simple and complex control systems in industrial automation.

Uses of This Programming Language

• Modeling of process control systems.
• Interconnection of function blocks for complex logic.
• Signal processing and filtering operations.
• Control of motor drives and actuators.
• Implementation of PID controllers and analog signal processing.

4. Sequential Function Chart (SFC)

SFC is a graphical language designed to model complex sequential control logic using steps, transitions, and actions. It resembles a flowchart, allowing for the hierarchical organization of control sequences and state-based programming. SFC is particularly useful for representing procedural control logic and coordinating multi-step processes in PLC programs.

Uses of This Programming Language

• Modeling of complex sequential processes.
• State-based control and hierarchical organization of tasks.
• Coordination of multi-step processes.
• Batch processing and recipe management.
• Implementation of state machines and event-driven logic.

5. Ladder Diagram (LD)

LD is a graphical language inspired by relay ladder logic, commonly used in PLC programming. It represents control logic using rungs composed of contacts and coils, resembling electrical schematics. LD is intuitive for electrical engineers and technicians, facilitating easy visualization and debugging of control logic in industrial automation applications.

Uses of This Programming Language

• Representation of relay logic control.
• Control of industrial machinery and equipment.
• Implementation of safety interlocks and emergency stops.
• Monitoring and control of sensors and actuators.
• Logical operations such as AND, OR, and NOT gates.

6. Structured Text (ST)

ST is a high-level, text-based language similar to programming languages like Pascal or C. It allows for structured programming with conditional statements, loops, and user-defined functions, facilitating complex algorithm implementation in PLC programs. ST is widely used for its readability, flexibility, and support for mathematical operations.

Uses of This Programming Language

• Data processing and manipulation.
• Task scheduling and time-based control.
• Advanced algorithm implementation.
• Error handling and fault diagnostics.
• Complex control and decision-making logic.

7. Sequential Textual Function Chart (SFC)

SFC is a textual representation of sequential control logic, offering a combination of structured text and sequential function chart elements. It enables programmers to express complex sequential operations using a textual format, providing clarity and flexibility in programming industrial automation systems. SFC enhances readability and ease of maintenance, making it suitable for modeling intricate process sequences and coordinating complex automation tasks.

Uses of This Programming Language

• Modeling complex sequential processes in a structured textual format.
• Coordinating multi-step operations with clear hierarchical organization.
• Representing procedural control logic for industrial automation systems.
• Enhancing readability and ease of maintenance in PLC programs.
• Facilitating the implementation of state-based control strategies and event-driven logic.

These languages provide different levels of abstraction and are suited for different tasks and programming styles. Engineers and technicians can choose the most appropriate language based on factors such as their familiarity with the language, the complexity of the task, and the requirements of the control system being developed.

Advantages of IEC 61131-3 Programming Languages

Here are some advantages of IEC 61131-3 programming languages:

• Standardization: Ensures compatibility and interoperability across different PLC platforms and vendors.

• Versatility: Offers a range of languages suitable for various programming preferences and tasks.

• Ease of Use: Provides both graphical and text-based languages, catering to different programming skill levels.

• Modularity: Supports modular programming, enhancing code reusability and maintainability.

• Comprehensive Functionality: Includes built-in functions and libraries for diverse automation applications.

• Real-time Capability: Designed to support real-time processing, ensuring precise control in industrial environments.

• Industry Acceptance: Widely adopted as the de facto standard in industrial automation, ensuring widespread support and resources.

Future Trends and Developments In IEC 61131-3 Programming Language

Future trends and developments in IEC 61131-3 Programming Language may include:

Integration with Industry 4.0: 

Enhancing compatibility with emerging technologies like IoT, AI, and cloud computing for smarter and more connected industrial systems.

Enhanced Visualization Tools: 

Introducing advanced graphical interfaces and visualization tools for easier programming and debugging of PLC applications.

Increased Use of High-Level Languages: 

Leveraging high-level languages like Structured Text (ST) for complex algorithm implementation and advanced control strategies.

Improved Safety and Security Features: 

Incorporating enhanced safety and security measures to mitigate risks associated with cyber threats and ensure reliable operation of industrial automation systems.

Support for Distributed Control Systems: 

Adapting the language to support distributed control architectures for scalability and flexibility in large-scale automation deployments.

Enhanced Real-Time Performance: 

Optimizing runtime environments and compilers to improve the real-time performance of PLC programs, ensuring precise control in time-critical applications.

Standardization of Advanced Features: 

Standardizing advanced features and functionalities across different PLC platforms to promote interoperability and facilitate seamless integration of automation solutions.

Conclusion

The IEC 61131-3 Programming Languages stand as a cornerstone in the realm of industrial automation, offering a standardized framework that ensures interoperability, versatility, and efficiency across diverse PLC platforms and applications. 

With a suite of languages catering to different programming preferences and tasks, IEC 61131-3 empowers engineers and technicians to develop robust, scalable, and maintainable PLC programs. 

As we move towards Industry 4.0 and beyond, the future of IEC 61131-3 promises integration with emerging technologies, enhanced safety and security features, and continued focus on user experience, ensuring its relevance and importance in shaping the future of industrial automation.

FAQs