Announcement

Collapse
No announcement yet.

HELP NEED - Modbus Communication with Mitsubishi VFD

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts


  • HELP NEED - Modbus Communication with Mitsubishi VFD

    Hi,

    I'm developing a program to connect my 6 Mitsubishi VFDs to communicate with Productivity P2000 PLC. BUT none of VFDs is communicating with my PLC..

    I connectted 6 VFDs to my PC through RS485-to-USB converter and used a modbus scanner on PC yesterday. And I was able to read and write holding register with 6 VFDs through PC.

    But none of these 6 VFDs is communicating with my PLC through Modbus. I'm really confused. I'm attaching the screen shot of my program.

    On my PLC, TX light is flickering, the RX light is not flickering at all, RX light is always on.

    All the Modbus communication parameters are the same as the PLC in Mitsubishi VFDs.

    This makes me confused and frustrated, why the VFDs can talk with my PC, but not with PLC?
    Any help would be appreciated.

    James
    Attached Files
    Last edited by James_wolfpack; 08-17-2016, 09:34 AM.


  • #2
    1) RX light on all the time is usually a sign of improper wiring. Check and make sure the "+"(TXD+/RXD+) and "-" (TXD-/RXD-) are connected properly to your drives.
    2) You do not state any distances to drives. If your wiring is correct, you may need to add termination resistors. See chapter 6 of hardware manual.
    3) I noticed in your screenshot of the MRX and MWX that one instruction is set up for "Zero Based Modbus Addressing" & one is set for "Modbus Decimal Addressing" refer to your drives and see which one they use. If you have working with Scanner for PC use the same setting for instructions as PC.
    4) For troubleshooting limit your network to a single drive and get it working and then use this as a template for the other drives.
    5) Increase your poll times if your are going to use automatic polling.
    6) I could not get the png of your cpu settings to open and it says the file is "0" in size. But make sure if you are talking to multiple devices to set the "Request/Response Delay" to something other than default. Usually start around 20-25 msec.

    Comment



    • #3
      Originally posted by PSeries_Eng View Post
      3) I noticed in your screenshot of the MRX and MWX that one instruction is set up for "Zero Based Modbus Addressing" & one is set for "Modbus Decimal Addressing" refer to your drives and see which one they use. If you have working with Scanner for PC use the same setting for instructions as PC.
      One rung is disabled, so it seems like OP is troubleshooting different configurations.

      Originally posted by PSeries_Eng View Post
      6) I could not get the png of your cpu settings to open and it says the file is "0" in size.
      Could not load it here either
      Last edited by kewakl; 08-19-2016, 05:50 AM.

      Comment



      • #4
        I would have a timer, use compare contacts to poll the drives.

        Comment

        Working...
        X