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A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis.
Function Block Diagram is one of five languages for logic or control configuration [2] supported by standard IEC 61131-3 for a control system such as a programmable logic controller (PLC) or a Distributed Control System (DCS). The other supported languages are ladder logic, sequential function chart, structured text, and instruction list.
While ladder diagrams were once the only available notation for recording programmable controller programs, today other forms are standardized in IEC 61131-3 (For example, as an alternative to the graphical ladder logic form, there is also a language more like C called Structured text within the IEC 61131-3 standard).
It is also possible to insert LD (Ladder Diagram) actions inside an SFC program (and this is the standard way, for instance, to work on integer variables). SFC is an inherently parallel programming language in that multiple control flows — Program Organization Units (POUs) in the standard's parlance — can be active at once.
Statement List (STL) - The program consists of a sequence of mnemonic codes of the commands executed one after another by the PLC. Ladder Diagram (LAD) - Graphical representation of the automation task with symbols of the circuit diagram; Function Block Diagram (FBD) - Graphical representation of the automation task with symbols to DIN 40700 ...
IEC 61131-3 is the third part (of 10) of the international standard IEC 61131 for programmable logic controllers.It was first published in December 1993 [1] by the IEC; the current (third) edition was published in February 2013.
For example, various electric and pneumatic transducers may fold and glue a cardboard box, fill it with the product and then seal it in an automatic packaging machine. PLC software can be written in many different ways – ladder diagrams, SFC ( sequential function charts ) or statement lists .
Example Ladder Logic Diagram The schematic diagrams for relay logic circuits are often called line diagrams, because the inputs and outputs are essentially drawn in a series of lines. A relay logic circuit is an electrical network consisting of lines, or rungs, in which each line or rung must have continuity to enable the output device.