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Help me: Connectivity issues between PLC and HMI?

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  • Help me: Connectivity issues between PLC and HMI?


    I recently took my PLC out of my office to the warehouse for testing, disconnecting it from my PC. However, I am now receiving a PLC Comm Error. I did not get this when the computer was hooked up. I'm having no programming issues - the program seems to be running, just not displaying any data on my HMI. Could this be a hardware issue? I suspect that the phone jack being used to connect my PLC and HMI is not doing its job - my theory is that it didn't receive the error when connected to the PC because the PLC was connecting to the HMI through the PC. Any thoughts on this diagnosis?

  • #2
    could be alot of things. an ip collision, faulty cabling, or miswired jacks. are the plc and hmi on a switch?


    • #3
      does the plc have a static ip address? taking it out of the office, and plugging it into the shop floor might have assigned it a different ip


      • #4
        I have heard that grounding can cause this. Maybe in the office, the grounding is great,, but in the warehouse, something is not grounded correctly and the electrical signaling is failing to get through.


        • #5
          What kewakl said. RS-232 is a ground referenced signal. Without a proper ground on all devices it won't work properly.
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