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Programmable Logic Controllers

Programmable Logic Controllers. Lecture 27 PLC Languages. Jesus is a friend who knows all your faults and still loves you anyway. But God demonstrates his own love for us in this: While we were still sinners, Christ died for us. Romans 5:8. Agenda. IEC 61131 Standard Programming Models

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Programmable Logic Controllers

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  1. Programmable Logic Controllers Lecture 27 PLC Languages

  2. Jesus is a friend who knows all your faults and still loves you anyway. But God demonstrates his own love for us in this: While we were still sinners, Christ died for us. Romans 5:8

  3. Agenda IEC 61131 Standard Programming Models Instruction List Structured Text Ladder Diagram Function Block Diagram Sequential Function Charts

  4. IEC 61131 Standard • Common and open framework • Loosely defined • Approved in 1992 • Six Main Components • - IEC 61131-1 Overview • - IEC 61131-2 Requirements and Test Procedures • - IEC 61131-3 Data Types and Programming • - IEC 61131-4 User Guidelines • - IEC 61131-5 Communications • - IEC 61131-7 Fuzzy Control

  5. Programming Models IL (Instruction List) ST (Structured Text) LD (Ladder Diagram) FBD (Function Block Diagram) SFC (Sequential Function Charts)

  6. Instruction List • Textual PLC Programming Language • Effectively Like Assembly Programming • Best Suited for Small Uncomplicated Programs • Instructions Consist of: • - Operator • - Modifier • - Operand • Example: AND NOT 00200

  7. Instruction List Example

  8. Instruction List Example 2

  9. Structured Text • Textual PLC programming language • Effectively like BASIC programming • Easiest to troubleshoot and understand • Useful for implementing calculation-intensive functions and other difficult functions • Instructions consist of constructs • Example: Analog_Out := Error * Gain;

  10. Structured Text * Sample Structured Text Code * (comments) VAR (variables) temp: INT; error: BOOL; END_VAR temp := %IW4; (addresses) IF temp > 3200 THEN error := TRUE; %QW := 200; ELSE %QW := temp / 16; END_IF;

  11. Ladder Diagram • Primary programming language • Resembles original relay logic documentation • Addressing and memory is different for every manufacturer • Ladder logic scanning (rung order vs. network column) • Not purely parallel processor like relay logic

  12. Ladder Diagram

  13. Function Block Diagram • Graphical data-flow programming method • Interconnected blocks • Similar to Ladder Logic

  14. Function Block Diagram Example

  15. Sequential Function Charts • Graphical method for structuring programs • Design tool for sequential problems • Consists of: • - Interconnected steps • - Actions • - Transitions

  16. Sequential Function Chart Example

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