You would be surprised the number of times asking yourself "Do I have current" will lead you to the problem with your program. I have a wire connected to my input modules common to complete the current path. I have a continuous path from my switch to my input terminal. My switch contact is allowing current to flow. Some people will say "Do I have voltage" but "Do I have current" is more thorough because it says: The best way to determine whether or not the input is on is to ask yourself, "Do I have current?". Now that we have added normally closed contacts, this would be confusing. In the last example of program flow we said since the button was "pressed" it wrote a "1" to the data box. The PLC updates its input data table values based off of the physical states of the inputs. Let's go through the program flow of the PLC while neither button is pressed.ฤก.
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