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Hi, please somebody should help me elaborate the ladder diagram attached.

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  • Hi, please somebody should help me elaborate the ladder diagram attached.

    Hi, i uploaded the attached program from Allen Bradley PLC Controlling a mixing batch, the HMI of the main panel is bad. i need somebody to help me elaborate more on this program in order to help me design a new HMI project controlling the mixing batch.

    i will appreciate any help
    Attached Files


  • #2
    I have limited experience, but wouldn’t finding the program of the original HMI be your starting point?

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    • #3
      If you can not get the screen program, you will have to reverse engineer what data points are needed in the HMI to control the PLC and display info.

      If commented PLC code is not available, populate the PLC program with comments to identify the control bits and numeric values that will need to be displayed or changed on an HMI.
      An electrical schematic with inputs and outputs will help with that.

      Choose a HMI and put the tags necessary into the HMI program. Import them or insert manually.
      Once you have the HMI working with some tags, run the HMI in monitor mode and check that the controls on the HMI change the correct control bits and numeric values in the program.

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      • #4
        You write the HMI is bad (dead LCD screen?). You maybe able to pull the program from it and reverse engineer a program for a C-more (since this is an AD forum).
        Why worry? If you've done the best you can, worrying won't make it any better

        - Walt Disney

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        • #5
          youre going to need to add tag names to your AB logic to make any sense of it. inputs and outputs as a minimum.(the stuff physically wired to the plc)

          if it was me id just replace the plc and the hmi and redo it completely. i hate trying to get into the middle of someone elses thought process. Youll end up with something that does exactly what you want, with commented files you can read and make sense of, much faster than trying to hash out whats in the AB.

          compare your AB io to the equivalent AD platform. a click or p1000 setup might get your job done pretty cheap, both retain the documentation internally, so even if the original is lost, the program as you documented can be retrieved.
          Last edited by quaizywabbit; 02-01-2019, 04:54 PM.

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          • #6
            Considering that the listing to OP provided is 105 pages and doesn't seem to include the 14 subroutines that are called (at least I didn't see any RET instructions, perhaps there are other was of handling subroutines?) I don't think rewriting the program for a different PLC is going to be too practical. But then I don't think reverse engineering it to setup a different HMI is not going to be easy either. I think the O.P. is going to have to pay the OEM whatever insanely inflated price they are charging for a new HMI. Assuming that is less than replacing the equipment entirely.

            What? the OEM doesn't exist any more or doesn't support that product ? I'm shocked (not)
            "controlling the mixing batch" doesn't tell us a whole lot about what is being controlled or how critical it is to the O.P.s operation, but I don't think the PLC/HMI problem is going to be cheap, high four to low (mid?) five figures wouldn't surprise me at all. Though my only experience with paying for contract programing was with a vision system which might command a higher price due to its specialization, so I could be off a bit.

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            • #7
              ok.
              line 000: when b3:25 turns on, then loads a 150.526 in f8:0
              lines 001-002 will latch b3:25 to 1
              lines 003-005 will start timers t4:99-101, if they are not already started
              lines 006-019 each makes a jump to a particular subroutine

              I would assume that once a jump to a subroutine is made, the program will resume to next line in the ladder with the return from subroutine.
              while the subroutine is executed, the plc will not reach the end of scan until the control is returned to main program.
              since you have so many subroutines, the scan time could be problematic. it is possible that a system watchdog could actually stop your plc due to exceeding scan time. if that dissent happen, then the watchdog timer must be disabled or dealt with somewhere else in your ladder program.

              to design the hmi
              it looks like if there is data exchanged with hmi, this happens in one or the subroutines.
              I am not sure I would program it the same way. reason: the plc program has to have certain components:
              1. configuration: this configures the program run, say according to the product it runts through the machine
              2. runtime adjustments: this makes adjustments in the synchronization of moving parts, or adjusts parameters like temperature, pressure, carbonation levels, servo axis offset, etc. these parameters can be adjusted at runtime and won't produce a mechanical crash of the machine
              3. emergency shutdown

              you should be able to exchange data from plc to hmi during the component 1 or 2 of the plc run.
              the program you've presented does not show this paradigm of programming. is kind of hard to read an understand it.

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              • #8
                These posts are always from low post count people that just plop some huge document on here and expect people to analyze it. Why bother? Has he responded yet? You all have better things to do with your time.

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                • #9
                  Originally posted by Adisharr View Post
                  These posts are always from low post count people that just plop some huge document on here and expect people to analyze it. Why bother? Has he responded yet? You all have better things to do with your time.
                  Thank you, I was worried.

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