PLC Programming

PLC Programming : There many languages to program a PLC like ST, FBD, IL etc. but most commonly used one is “LADDER” Language. As the name suggests, program in this language is built like ladder. Two vertical lines called rails and in between various horizontal lines called rungs.


Symbols:       
NC
Normally Close
(Examine if Open)
NO
Normally Open
(Examine if Close)
Coil
Coil




These are three basic symbols used in LADDER programming. 

NORMALLY OPEN:-  A  normally open contact corresponds to the use of the direct state of the input. If the input is supplied, the contact is said to be conducting.
NORMALLY CLOSED:-A normally closed Contact corresponds to the use of the reverse state (logical complement of the direct state) of the input. If the input is supplied, the contact is said to be non-conducting.

COIL:- Outputs correspond to the smart relay output relay coils. 

Programming Examples: 
1. Make a Ladder Logic in which when we press a NO switch Outputs turns ON while on releasing that switch output will turn OFF.




2. Make a Ladder Logic of AND gate (i.e. there are inputs and one output, when we both inputs are OFF or any one input is ON, output should not turn ON. When both inputs are switched ON output should turn ON.)






3. Make Ladder Logic of OR Gate.






4. Make Ladder Logic of NOT Gate (i.e. when input is pressed output turns OFF and if input is released o/p turns ON).



In this circuit we are using NC contact.


watch this video to understand better - Click Here to watch Video


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