For the last few months we have been discussing PLC programming and how to begin PLC programing. Today we will try to understand one basic concept of the PLC Programming ,most of us who are beginners in PLC Programming make this mistake. So we will understand the basic concept behind this plc program.
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Solve this Sample PLC Program :-
See the below PLC program :-
Note :- CLICK ON IMAGE TO MAGNIFY
Can you guess the output of this plc program?? If you see the above program carefully then we find that output y1 is used twice in the program and if u recall the scan cycle then from scan cycle we understand that the image of the output which is near to end rung is maintained i.e whatever the sate of output y1 connected in last rung is that will be maintained all the time irrespective of its state at rung 1.
Most of us who begin plc programming make this mistake , so we should never connect the same output at two places in the plc program.
So when we press the X0 then the output Y0 will latch but the output Y1 will not be on ( because the state of output Y1 at rung 2 is OFF ) and when we press X1 then the output Y0 will unlatch and output Y1 will be on for the time X0 is pressed.
You have to be familiar with PLC Hardware and its basic function to understand the above. But at this point of time just make one habit that never use the same output at two places in a plc program. Also beginners can see the omron PLC and its addressing method & Best PLC programming books, to get more familiar with plc programming.
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