Function Block

Function Block

A Function Block is a fundamental concept in the field of PLC (Programmable Logic Controller) programming. It refers to a pre-programmed routine that executes specific control functions, such as timers, counters, or PID (Proportional-Integral-Derivative) control. Function blocks are designed to encapsulate a set of operations or calculations that can be reused across different parts of a PLC program. This modular approach simplifies the design and maintenance of complex control systems by allowing programmers to build robust, scalable applications without having to rewrite code for common tasks. Function blocks are visually represented as blocks in graphical programming environments, making them intuitive for engineers to implement and understand.

Common Applications

Timers and Counters

Function blocks are frequently used to implement timers and counters in PLC systems. These blocks can handle delays, measure intervals, or count events, providing essential control for processes requiring precise timing or event tracking.

PID Control

In industrial automation, PID controllers are vital for maintaining desired levels of temperature, pressure, flow, and other process variables. Function blocks dedicated to PID control simplify the integration and tuning of these controllers within a PLC program.

Motion Control

Function blocks are used in motion control applications to manage the movement of machinery, such as robotics and conveyor systems. They allow for the precise control of speed, position, and acceleration.

Safety Considerations

Consistency and Testing

While function blocks can streamline programming, it is crucial to ensure that they are correctly configured and tested to prevent unexpected behavior in control applications. Testing should cover all possible input scenarios to maintain system reliability.

Version Control

When using function blocks from libraries or third-party vendors, it is important to manage versions carefully. Updates to function blocks can introduce changes that might affect system performance or safety, making thorough review and testing necessary before deployment.

Related Terms or Concepts

Ladder Logic

A graphical programming language used in PLCs that can incorporate function blocks. Ladder logic represents control schemes using symbols resembling relay logic diagrams.

Structured Text

A high-level textual programming language used in PLCs that can define complex algorithms and logic, often incorporating function blocks to simplify repetitive tasks.

IEC 61131-3

An international standard for PLC programming languages, which includes function block diagrams as one of its five programming paradigms, promoting consistency and interoperability across different PLC systems.