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PLC output, or MODBUS

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  • PLC output, or MODBUS

    Hi.
    CLICK RS485 to SureServo drive.
    Internal index selected.
    Now I have a PLC OUT to physical DI to the drive to trigger the move.
    To simply pulse the out bit is too fast so I have a short timer to lengthen the signal to be sure its seen.
    Would it be better/faster to send the trigger signal through Modbus directly to the address of the trigger in the drive ?
    Maybe eliminate the timer ? (and the wiring)
    Thanks,
    TS

  • #2
    A digital output is much simpler if all you need to do is trigger a move. If there are other functions in the drive that you'd like to PLC to control then the complexity of a communications based approach would probably be well be justified, but for single function I wouldn't bother.

    I should mention that my opinion is based on working with other brands of drives where documentation was marginal, probably wouldn't be so bad with a SureServo where the manual gives examples of using some ADC PLCs (but not the CLICK)

    Oh, just checked, while the manual doesn't include the CLICK, application note AN-SERV-009 does, so I guess using MODBUS shouldn't be too difficult after all. Still, if I was triggering only a single function I think I still use a discrete output.
    Last edited by Tinker; 03-12-2020, 04:16 PM. Reason: addition

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    • #3
      The issue is that when using the pulse of the physical Y output of the PLC to the wired DI of the drive, I suppose its too fast and the drive doesn't see it.
      I have to keep that Y on for a spell, currently 100ms with a timer.
      Just wondering if the Virtual DI would see the pulse from the PLC without using the timer. (IF I can get the virtual DI's to work ... a different topic)
      Thanks Tinker

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      • #4
        The drive has debounce/noise filtering on its digital inputs (see parameter P2-09) default is 4mS, which is less than a typical CLICK scan time. I looks like setting the filter to zero is an option, and since a transistor PLC output doesn't bounce one could try that, but the same setting applies to all the general purpose inputs, so if any do have mechanical switches, then 0 might be a problem. Since the CLICK has the potential for 500 timers just using a timer seems reasonable.

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