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4 pump alternator

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  • 4 pump alternator

    I need help debugging logic ive written for this alternator, im new to this so this should be a simple resolve for some of the more experienced programmers in here...also how do i load a copy for memebers to view and comment


  • #2
    Alternator.pdf
    Above is the logic so far. Problem is the counter locks up when C0 is energized,
    Attached Files
    Last edited by Robfig80; 11-22-2018, 11:30 AM.

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    • #3
      C0 is locking up CT0 because the counter wants transitions. You'd need to change the C0 contact to a one-shot.

      Other thoughts:

      Currently, your logic will only run one pump (though you call it "lead" so you may be planning to add more). Any pump alternator I've ever done uses all the pumps for capacity control as well as alternation. Also, if it were my logic, I'd want to first figure out how many pumps to run (time above level setpoint, maybe combined with how far above setpoint, rate of change, etc.). THEN, once you've decided you want two pumps operating out of the four, or whatever, have other logic dedicated to selecting which ones based on Auto Mode, Fault, alternation, etc. There's something foggily in the back of my mind about it being better for some reason to track the most recent pump to turn off rather than to turn on, but I can't remember why.

      Finally, there are several ways to treat alternation. Strictly round-robin, accumulated run-time control, etc. I think there's a flaw in one common way run-time control is implemented; people often try to keep resource run times equal. I think that's a flaw. Lets say you think a reasonable life between service/replacement/whatever is 20,000 hours. If you maintain equal run-times, then all the pumps hit 20k hrs simultaneously, thus increasing the chance of multiple near-simultaneous outages, whether planned (rebuild) or unplanned (failure). I think that if the target is 20k hrs, and you have four pumps, then you want the run-times separated by 5k hours, unless the system is so large that the logistics per downtime are dominant over per unit. Even in that case, I'd still maintain an offset, but not t/n, maybe t/5n or something.

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      • #4
        I have tried making C0 a one shot with no avail.. Is it possible that I am having problems because it being executed in a Do-More simulator ?

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        • #5
          Originally posted by Robfig80 View Post
          I have tried making C0 a one shot with no avail.. Is it possible that I am having problems because it being executed in a Do-More simulator ?
          C0 has to turn off and back on to trigger the count. A one shot doesn't help if you don't turn back off.

          The 'simulator' isn't really a simulator. It is the full Do-more engine minus the hardware acceleration features and it behaves identically to the PLCs.

          I'd do this as a Stage program.
          Last edited by BobO; 11-22-2018, 05:25 PM.

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          • #6
            Wouldn’t be easier if you described your sequence of operations with words? You provide a program and expect someone else to figure out the sequence of operations, from a program obviously flawed.
            please be so kind to explain the process first.

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            • #7
              Your logic in Post 2 looks to work just fine as-is with the addition of a normally closed C0 before Out C0 in Rung 12.

              This forces C0 back off after one scan. Since the counter value changes, at most the rung can only be true every other scan and it will cycle CT0 rapidly if no pumps are available.

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              • #8
                Thanks for all the suggestions and feed back! I've worked with PLC for a long time on the hardware install and process wiring along side many system integrators. I've slowly been picking up on the "software" end of it by asking a lot of questions while trying no to be an annoyance. I am able to apply a lot of what I know about relay logic but I find that programming definitely takes a different mindset when it comes to getting things done. All of which I find extremely interesting and intriguing to say the least. I've written smaller programs using the Click PLC and simple ladder logic to control various equipment including the panel that will eventually send the level signal to these pumps. Thanks again everyone, knowing that there are people such as yourselves willing to help someone learn and trouble-shoot makes someone with no formal training want to push further and learn more.

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