Function Block Programming Techniques

Understanding Function Block Programming in Industrial Automation

Function Block Programming (FBP) represents one of the five standardised programming languages defined by the IEC 61131-3 standard, and it has become an essential tool for automation engineers across Atlantic Canada's growing industrial sector. From food processing facilities in Nova Scotia to manufacturing plants throughout the Maritimes, function block programming offers a visual, intuitive approach to developing complex control systems that are both maintainable and scalable.

Unlike ladder logic or structured text, function block programming uses a graphical representation of interconnected blocks, each performing a specific function. This approach mirrors the way engineers naturally think about control systems—as interconnected components working together to achieve a desired outcome. For facilities managers and technical teams in the region, understanding these techniques can significantly improve operational efficiency and reduce costly downtime.

Core Principles of Function Block Architecture

Function blocks operate on a fundamental principle: encapsulation of functionality. Each block contains inputs, outputs, and internal algorithms that process data according to predefined rules. This modular approach allows engineers to build complex control strategies by connecting simple, well-understood components.

Block Structure and Data Flow

A standard function block consists of several key elements:

• Input parameters: Variables that receive data from other blocks or system sensors, typically positioned on the left side of the block

• Output parameters: Processed results that can be passed to other blocks or used to control actuators, positioned on the right side

• Internal variables: Data stored within the block that maintains state information between execution cycles

• Algorithm: The processing logic that transforms inputs into outputs according to specific rules

Data flows from left to right in function block diagrams, creating a natural reading order that simplifies troubleshooting. When properly implemented, a technician at a Nova Scotia fish processing plant, for example, can quickly trace signal paths and identify potential issues without extensive programming knowledge.

Execution Order and Scan Cycles

Understanding execution order is critical for reliable function block programming. Most PLCs execute function blocks in a predetermined sequence during each scan cycle, which typically ranges from 1 to 100 milliseconds depending on the application requirements. In high-speed packaging lines common in Maritime food processing facilities, scan times of 5-10 milliseconds ensure responsive control.

The execution sequence follows the data flow path, ensuring that upstream blocks complete their calculations before downstream blocks require their outputs. Modern PLC platforms automatically determine optimal execution order, though engineers can manually specify priorities for time-critical applications.

Essential Function Block Types for Industrial Applications

Successful automation projects rely on a library of well-designed function blocks. Understanding the capabilities and proper application of standard blocks forms the foundation for more advanced programming techniques.

Timer and Counter Blocks

Timer blocks are fundamental to virtually every automation application. The IEC 61131-3 standard defines three primary timer types:

• TON (Timer On-Delay): Delays the activation of an output by a specified time, commonly used for motor start sequences or equipment warm-up periods

• TOF (Timer Off-Delay): Maintains an output for a specified duration after the input deactivates, useful for cooling fan run-on or conveyor clearing operations

• TP (Pulse Timer): Generates a fixed-duration pulse regardless of input duration, ideal for triggering discrete events like actuator strokes

Counter blocks track events and quantities, essential for batch processing operations. In Atlantic Canadian beverage production facilities, counters monitor bottle counts per case, cases per pallet, and production totals per shift with accuracies exceeding 99.99 percent when properly implemented.

Mathematical and Logical Function Blocks

Mathematical function blocks perform calculations ranging from basic arithmetic to complex trigonometric functions. These blocks handle scaling operations—converting raw analog inputs from 4-20 mA signals (0-32767 digital counts) to engineering units like temperature in degrees Celsius or pressure in kilopascals.

Logical function blocks implement Boolean operations (AND, OR, NOT, XOR) that form the decision-making backbone of control systems. Combining multiple logical blocks creates complex conditional sequences while maintaining visual clarity in the programming environment.

PID Control Blocks

Proportional-Integral-Derivative (PID) control blocks are essential for process industries throughout Nova Scotia. These sophisticated blocks continuously calculate error values and apply corrective outputs to maintain setpoints. Typical applications include:

• Temperature control in food processing with accuracy requirements of ±0.5°C

• Pressure regulation in pneumatic systems maintaining ±2 percent setpoint accuracy

• Flow control in water treatment facilities handling 500-5000 litres per minute

• Level control in storage tanks with deadband settings of 1-3 percent

Modern PID function blocks include auto-tuning capabilities that can determine optimal gain values (Kp, Ki, Kd) within 3-5 process cycles, significantly reducing commissioning time for new installations.

Advanced Programming Techniques and Best Practices

Moving beyond basic function block implementation requires understanding advanced techniques that improve code quality, maintainability, and performance.

Creating Custom Function Blocks

While standard libraries cover most common requirements, complex applications often benefit from custom function blocks tailored to specific processes. When developing custom blocks for Maritime industrial applications, engineers should follow these guidelines:

• Single responsibility principle: Each block should perform one well-defined function, typically requiring no more than 10-15 inputs

• Comprehensive error handling: Include status outputs indicating normal operation, warnings, and fault conditions

• Documentation: Embed detailed comments explaining input/output relationships, valid ranges, and expected behaviour

• Version control: Implement naming conventions that track block revisions (e.g., FB_MotorControl_v2.3)

• Testing protocols: Develop standardised test procedures covering normal operation, boundary conditions, and failure modes

A well-designed custom function block for motor control might include inputs for start/stop commands, speed reference (0-100 percent), and enable signals, while providing outputs for running status, actual speed feedback, current draw, and fault codes. Such blocks can reduce programming time by 60-70 percent when applied across multiple similar drives in a facility.

Hierarchical Programming Structures

Large automation projects benefit from hierarchical organisation, where function blocks are nested within larger control modules. This approach mirrors the physical structure of industrial facilities—individual function blocks control specific devices, groups of blocks manage process units, and higher-level blocks coordinate entire production areas.

For a typical Nova Scotia seafood processing facility, this hierarchy might include:

• Level 0: Individual device blocks (valve control, motor starter, sensor scaling)

• Level 1: Equipment modules (conveyor section, refrigeration unit, packaging machine)

• Level 2: Process cells (receiving area, processing line, cold storage)

• Level 3: Area coordination (production scheduling, recipe management)

Integration with Modern Control Platforms

Function block programming does not exist in isolation. Modern automation architectures require seamless integration with supervisory systems, databases, and enterprise networks.

Communication and Data Exchange

Contemporary function blocks must handle communication protocols prevalent in Atlantic Canadian industrial facilities. Common integration requirements include:

Ethernet/IP and Modbus TCP: These protocols dominate Maritime industrial networks, with typical cycle times of 10-50 milliseconds for discrete I/O and 100-500 milliseconds for analogue data. Function blocks must accommodate network latency without compromising control stability.

OPC UA connectivity: The emerging standard for industrial interoperability, OPC UA enables function blocks to expose data to higher-level systems securely. Implementing OPC UA server functionality allows SCADA systems and historians to access real-time process data without custom driver development.

Database logging: Function blocks can trigger data logging events, capturing critical process parameters at rates from once per second to once per hour, depending on regulatory requirements. Food safety regulations in Canada often mandate temperature logging at minimum 15-minute intervals for critical control points.

HMI Faceplates and Operator Interfaces

Each function block should have a corresponding HMI faceplate that provides operators with appropriate visibility and control. Well-designed faceplates display current status, setpoints, and alarm conditions while restricting access to parameters based on user authentication levels.

Standard faceplate designs improve operator training efficiency—a technician familiar with the motor control faceplate at one facility can immediately understand the same interface at another location, reducing training time by an estimated 40-50 percent.

Troubleshooting and Maintenance Considerations

The true value of function block programming becomes apparent during troubleshooting and maintenance activities. Properly structured programs significantly reduce mean time to repair (MTTR) and improve overall equipment effectiveness (OEE).

Diagnostic Function Blocks

Dedicated diagnostic blocks monitor system health and provide early warning of developing problems. These blocks analyse patterns in process data, comparing current behaviour against established baselines to detect anomalies before they cause failures.

For example, a pump monitoring function block might track:

• Motor current relative to flow rate (detecting impeller wear or blockages)

• Vibration trending over time (predicting bearing failures 2-4 weeks in advance)

• Start time duration (identifying mechanical binding or electrical issues)

• Operating hours and start counts (triggering preventive maintenance alerts)

Online Modification Capabilities

Modern PLC platforms support online changes to function block programs without stopping production. This capability is particularly valuable for Nova Scotia's seasonal industries, where processing facilities operate continuously during peak periods and cannot afford unscheduled shutdowns.

When performing online modifications, engineers should follow strict change management procedures:

• Document all changes in a maintenance log with timestamps and justification

• Test modifications in simulation mode when possible before deployment

• Implement changes during low-production periods to minimise risk

• Maintain backup copies of original programs before any modifications

• Verify proper operation through systematic testing after implementation

Future Trends and Emerging Technologies

Function block programming continues to evolve alongside broader Industry 4.0 initiatives. Engineers serving Atlantic Canada's industrial sector should prepare for several emerging trends that will shape automation practices over the coming decade.

Artificial intelligence integration: Machine learning algorithms are being packaged as function blocks, enabling predictive maintenance and process optimisation without requiring data science expertise. These blocks analyse historical data patterns and automatically adjust control parameters for optimal performance.

Cloud connectivity: Function blocks with native cloud communication capabilities allow remote monitoring and analysis of equipment across geographically dispersed facilities—particularly relevant for companies with operations throughout the Maritime provinces.

Simulation and digital twins: Advanced function block libraries now include physics-based models that enable comprehensive testing before deployment. Engineers can validate control strategies against virtual equipment, reducing commissioning time by 30-50 percent on complex projects.

Cybersecurity features: Modern function blocks incorporate security measures including encrypted communications, access authentication, and anomaly detection to protect critical infrastructure from cyber threats.

Partner with Experienced Automation Professionals

Implementing effective function block programming requires expertise that balances theoretical knowledge with practical experience in real-world industrial environments. The techniques discussed in this article represent proven approaches that deliver measurable improvements in system reliability, maintainability, and performance.

For industrial facilities throughout Nova Scotia and Atlantic Canada seeking to optimise their automation systems, Sangster Engineering Ltd. offers comprehensive engineering services backed by deep regional expertise. Our team understands the unique challenges facing Maritime industries—from harsh coastal environments to seasonal production demands—and develops automation solutions tailored to these specific requirements.

Whether you are implementing a new control system, upgrading legacy equipment, or seeking to improve existing automation performance, contact Sangster Engineering Ltd. in Amherst, Nova Scotia, to discuss how professional engineering services can support your operational goals. Our experienced team is ready to analyse your requirements and develop function block programming solutions that deliver lasting value for your facility.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.