Hello, I need help to solve a problem. Here is the isuue : operator should press a button once to trigger an output, but instead of once they are clicking that button several times at the same time which is effecting the Program. I want to add a condition in the program so that clicking several times will not cause any issue. How can I do that or how can I disable the button for few seconds so that they can not press that button just after one press(button is created using factory talk HMI). Thanks in advance.
Last Edit: Oct 31, 2018 11:48:21 GMT -8 by sanjana
There are literally 10+ ways to solve this. The proper way would be in the PLC/PAC program itself, although one could write some code in HMI. Within the PLC/PAC program, the proper way is to find everywhere in the PLC program that input from HMI is being used, see which one is improperly written. The PLC ladder logic is a sequencer (and PLC being emulated by a PAC is also a sequencer). Therefor if program was properly written, you would never see the problem you describe. If you do not have access to PLC ladder logic or do not have enough training for this simple fix, contact the vendor who sold you the machine and ask them to fix their ladder logic.
A simple example of properly written logic that multiple presses of button have no negative effects on program operations is the most commonly used function of a Start, Stop Run circuit.
Look at this programming example. www.slideshare.net/bin95/plc-programming-example-hydraulic-press , Rung zero uses a start button input, which feeds the seal in rung of logic. Once the start button is pressed, the branch seals in below it, so no mater how many times operator presses it, it has no effect. Not until the run sequence is stopped, then next scan cycle the rung (and Run output) will energize if start is pressed again. For those new to electrical circuits and PLCs, see
Another common example is motor starter circuits. (Anything that is a an electrical circuit diagram is directly translatable to plc ladder logic.) See ...
If they used best practices, so have an i/O cross reference subroutine where the input from HMI (N7:35/4) is only used once in the program, then referenced everywhere else in the program via an internal bit ( like b3/27 for example), you can add a branch around it and another branch around the internal output bit with timer so it ignores multiple activation of the input/hmi button.
Or you could use a more complicated JK flipflop circuit approach, etc. Like I said, at least 10 different ways you could solve this, above are just a few in order of best way to less best way.
Last Edit: Nov 5, 2018 15:04:02 GMT -8 by profbyrd