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RS-485 multi-drop wiring /Click / EA9 - I can't make it work!

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  • RS-485 multi-drop wiring /Click / EA9 - I can't make it work!

    Hello all;
    Okay, I know I'm just doing something simple wrong here, but I'll be damned if I can find what. I've gone through all the documentation I can find here, but I cannot get a Click's RS485 port (port 3) to talk to an EA9's RS485. I have the recommended Belden cable, the proper resistors to match that cable's characteristic impedance, set up comm ports to matching settings, and tried all manner of node#s. I've also tried connecting a Click to an Allen Bradley Powerflex and couldn't make that work either. Click's Modbus "send" instruction just returns a "fail" flag. Is there anything I am overlooking?

    Just to try something different, I did connect two Clicks via port _2_ and use some Modbus instructions, and at least the units saw each other. But what I really need is to get my 2 Clicks and my EA9 networked together, thus the multi-drop option.

    Although this is my first foray into RS485, I've many years' experience with serial comms, having wired up all manner of funky cabling for programming two-way radios and such, so I'm comfortable setting two comm ports up and running a little cable. But... obviously I have something wrong here.

    Any thoughts on where I've gone wrong?

    Thank you!
    Brian


  • #2
    Originally posted by Vintovka View Post
    Hello all;
    Okay, I know I'm just doing something simple wrong here, but I'll be damned if I can find what. I've gone through all the documentation I can find here, but I cannot get a Click's RS485 port (port 3) to talk to an EA9's RS485. .... Click's Modbus "send" instruction just returns a "fail" flag. Is there anything I am overlooking?
    Yep, you are overlooking something, the EA9 must THE master ("There can only be one") the CLICK can not use the "SEND" instruction, it must only speak when spoken to.

    Actually though, I can't quite imagine what you'd be trying to send to a C-More anyway, since the C-More is always the master, the addresses of it data are not documented that I know of.
    Well, there is that option in the panel setup to "connect through another panel" (which I have not used) so it would seem that a C-More can talk to another C-More, but that function would not be applicable to a CLICK

    EDIT:, Oh, I missed the "2 CLICKS", if you want to transfer data from one CLICK to the other, you will have to let the C-More do it via "tag copy" in the "event manager", both CLICKs will be slaves to the C-More. Or, alternatively, at the same time that both CLICKs are slaves to the C-More on the multi drop RS485, they could also be connected to each other via RS232 and one (but only one) could use "SEND" to talk to the other.
    Or, to be really weird, you could use all the ports on the CLICKs, port 3 to the C-More, port 2 of CLICK1 to port 1 of CLICK2 and vice versa, then either CLICK could talk to the other, and the C-More cold talk to both CLICKs.
    Last edited by Tinker; 11-07-2014, 08:42 PM.

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    • #3
      Tinker, thanks for the reply. The information about using the EA9 to move data via "tag copy" is a piece of the puzzle I will need later, thanks.

      But putting aside all the more complex versions of this effort, when I am simply connected Click to Ea9, with nothing else going on, nothing else connected... I have no comms. On the top of the EA9's screen I just get the message about having lost communications with the PLC. I have 3-wire Belden cable recommended by AD's literature, and 120-ohn resistor between + & - at each device connector. Ea9 was set to master (well, I tried everything), and Click as node 2, (although again I tried multiple node #s).

      So just with that limited scenario, is there anything I'm missing?

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      • #4
        I suppose you have checked the wiring polarity? While the +/- is marked on the CLICK, it is not on the 8" EA9 I have (top pin is + )

        "nothing else going on"


        Is that "SEND" instruction still in the PLC program? The CLICK must be in slave mode for the C-More to communicate with it, the "SEND" instruction puts in master mode, though I'm not sure just when, perhaps only when the "SEND" is active.

        I happen to have an EA9 and a CLICK sitting on my desk, and just tried it.
        A never activated "SEND" instruction has no effect, but a SEND that was activated, even if later deactivated, will cause a communication timeout until power is cycled on PLC (simply loading a new program without any "SEND" will NOT fix the problem, power has to be cycled)

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        • #5
          I just recently installed a similar setup this summer. Tinker is right in saying the c-more panel is the master and no send or receive instructions are needed between the click plc and the EA-9. I connected two click plc's together via the RS-232 ports and wrote a subroutine strictly for the their communications. I suspect you might not be using port 1 on the panel for your RS-485 connection to the plc. If that is the case you will need to order a DSUB port adapter from Automation Direct Part# EA-COMCON-3A . You will also have to go to the panel manager in the C-More software and set port 1 for use as RS-485 communication. Hope this is helpful. I'll check back to see if you have anymore questions.

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          • #6
            One other thing is the node address. Set the C-more to node 1 and the Click as node 2 in your com port settings.

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