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Counter Ladder Programming Question

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  • Counter Ladder Programming Question

    Hey guys,

    I'm trying to use a up counter with a single sensor to trigger several outputs one after the other. So once an object goes by a sensor, gates will open one at a time in sequence. So if there are four gates, counter event 1 opens the first gate for one second, counter event 2 opens the second gate and so on. The problem is that the previous gate needs to close (open a relay) once it's sequence has run.

    I can get them to open one at a time using multiple counters, but releasing the previous gate without it triggering again until all four gates have done their thing is where the problem lies.

    Any thoughts or advice on this would be greatly appreciated!

    Jeremy

  • #2
    Any time I hear the word “sequence”, my first thought is either stage or drum. I probably need a better understanding of the conditions to open and close each gate before making a recommendation.

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    • #3

      One method for a smaller amount of steps would be to use numeric value as a status.

      Start with zero when program starts.
      When Sensor is triggered, increment by one.

      When status = 1, set Gate 1 and start timer
      Timer is made, increment status

      When status = 2, reset Gate 1
      set Gate 2 and start timer
      Timer is made, increment status

      When status = 3, reset Gate 2
      set Gate 3 and start timer
      Timer is made, increment status

      When last gate is completed, set status to zero and wait for sensor trigger.

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      • #4
        Is this the same system with the color sensing you posted earlier this month? If so a diagram of the system might help.
        thePLCguy

        Bernie

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        • #5
          Hi RogerR,

          I think that is what I'm trying to do, but I'm not sure how to go about it. I don't know how to use the individual increment numbers independently of the counter. I will upload my code shortly.

          Regards,
          Jeremy

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          • #6
            Hi bcarlton,

            Same system, but without the color sensor as we are waiting for it to arrive. I am working on an assignment that we can do in the meantime.

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            • #7
              Here is my code so far. I'm using Do-More Designer.
              Attached Files

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              • #8
                Looking at your program it appears to be a 'proof of concept' type setup. You seem to be placing disks on a conveyor every 3 seconds. It looks like you are beginning to write a sequence where every other disk is pushed at gate 3 and every remaining disk at gate 4. Your use of the flasher command at the gates is a little different. In rung 8 the output to Y0 (Gate 4) is conditioned by the Normally Closed of an undefined output. X4 and X5 are named for gates. Precisely what are they sensing relative to each gate?
                thePLCguy

                Bernie

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                • #9
                  It's just a setup to teach the basics of PLC's to my electrical class at the Tech College I work at. I need to learn how to use timers for the gates, but they weren't working the way I needed them to so I fudged a bit. I finally got this working by only sending a signal to a gate when the counter was on a certain number using the "equal to" bit. Then I used a one-shot to turn the constant signal to a momentary signal that triggers the flasher/timer.

                  Thanks for the input. i will load the complete code here when i get a minute so you guys can tell me what I need to do to actually do it right! lol

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                  • #10
                    im thinking a drum instruction can handle what you wanna do

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