PLC Programming Practice-PLC programming languages

PLC programming languages are defined by the international electrotechnical commission (IEC) under sections 61131-3 standards are explained below.

1. Ladder logic (LD)
Ladder logic (LD)

●      Modeled from relay logic panel.
●      Easy to understand and troubleshoot.
●      Difficult for motion and batching programming
2. Sequential function chart (SFC)
●      Language is similar to flow charts.
●      The process can be broken into steps.
●      To have direct access to the logic for a piece of equipment fault.
●      Minimal programming effort and greater clarity through graphic programming.
●      Excellent legibility for maintenance personnel.
Sequential function chart (SFC)
●      Less time in the commissioning phase thanks to the graphical programming interface.
●      Minimal implementation effort because there are few possibilities for errors when generating code.
●      High availability of the machine through process diagnostics functions (interlock and supervision).
●      Fast error detection through PLC code display and criteria analysis on the HMI.
3. Functional block diagram (FBD)
Functional block diagram (FBD)
●      FBD describes functions between inputs and outputs that are connected by connection lines.
●      It is in the graphical form language with repeated blocks.
●      It is good for motion control programming.
●      It can combine many lines of the program into a single block.
●      But it is difficult to troubleshoot using this language.
4. Structured text (ST)
Structured text (ST)
●      Similar to C language, this language uses instructions like- for, while, if, else, case, if-else, etc.
●      Very organized and good for computing large mathematical calculations.
●      It covers some instructions that are not available in the ladder diagram.
●      It is difficult to edit online.
5. Instruction List (IL)
Instruction List (IL)
●      Instruction list language consists of predefined instructions, which are used to program a PLC.
●      The use of instructions makes this program very compact.
●      It is difficult to edit online.

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