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  • Sourcing input DC wiring question

    I'm sure this is a supremely basic question but I think my problem is I'm an engineer and overthinking things. I'm used to embedded applications where every nuance of any circuit is all handled during design and nothing is supposed to connect and "just work".

    This circuit should work, yes? When the oven is "moved forward", the limit switch supplies ground to the bottom of the relay's coil and the 24VDC engages the relay. Now the "Oven is FWD" relay is switched on and the PLC can observe there is an input present.

    Click image for larger version

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    Also, I'm assuming the CLICK can "talk to" a SL9696... can it also talk to the GS1 VFDs? Or is there another product I should use. I'm also thinking about the DoMore BRX... I need to make a full list of the inputs that would be configured as above.


    I'm thinking that I can start off with this hybrid kind of circuitry where the PCL and HMI can offer automated interfacing with the equipment while keeping the fundamental circuits physically laid out. In theory, the above circuit would work with or without the PLC (obviously, with the PLC removed, that 24VDC needs to be connected to the relay's coil).


    I've got a plastic molding machine and all of the controls are discrete logic using relays and switches. The non-analog part is the SL9696 temperature controller and I set it via its front panel. And there are a few VFDs. I started the wind up to this question with a post to General Applications. My goal is to use an HMI to display status and allow single button programming of the SL9696 temperature controller for the different modes of operation. Another part of this is to monitor the safety train via the PLC. I have decided that rather than "trust" my logic to give the final GO/NO GO to the burner, I would implement the safety train via relays. Currently, the 115V to feed the flame controller goes through each step of the train. I'd like each sensor switch to be its own input and then use relays adjacent to the PLC to chain the 115V to the controller.

    Thanks,
    Chris


  • #2
    C1 should be going to the negative (0v) of your DC supply.

    Your limit switch should be powered by +24v, and have the other wire go to X1. I would wire one side of your relay to 0v, and the other to Y1, and have +24v connect to C3. Then program the Click to close the relay when the limit switch is true. I write this as it's not a good idea to have a relay coil connected to an input, as it could damage the input when the coil de-energizes.

    You can use port 2 or 3 to control a GS1 using Modbus read and writes. I've done it many times.

    - Todd
    If you've done the very best you can, worrying won't make it any better - Walt Disney

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    • #3
      Hi Todd,

      Thanks for writing -- and helping my learning curve avoid that big mistake.

      Do you mean something like this:

      Click image for larger version

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      I have more than 8 inputs ... I'll add more I/O as needed but there are only a few more than 8. All the switches are intended for 115VAC up to 4A so I'm not worried about taxing them; just hope they are good enough to act as inputs when 24V comes through.

      Thanks,
      Chris

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      • #4
        Since the outputs are sinking, Y1 will be providing 0v, so where you show your green wire from your relay going to ground, it will actually go to +24V. Otherwise, all looks good.

        - Todd
        If you've done the very best you can, worrying won't make it any better - Walt Disney

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        • #5
          Use the CLICK RS-485 Port 3 to communicate with the SOLO (SL9696) controller. You may want to set a low baud rate for communication reliability (i.e. 9600 baud). Sending/receiving should only take 10-20 milliseconds with excellent reliability. Remember to terminate both ends of the twin wire 485 loop with 120 ohm resistors. Attached is a sample of one way to send a value to a SOLO.

          Also, the Automation Direct folks told me to add a 10 ms delay after the call to the built-in CLICK Port 3 (_Port_3_Ready_Flag) to accommodate the faster clock rate on the Ethernet-equipped CLICK CPUs; that 10 ms gives the CLICK internal I/O processor chip time to respond reliably.


          Click image for larger version

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          • #6
            Todd and slb9, thank you very much for suffering my newb questions and helping me get a start in this strange new (for me) world. Friendliness like this is why I come to AD first when it's time to spend my work's money. I'm a pretty smart guy, but am the most stupid when it comes to new "things". Believe it or not, "terminal blocks" are so flexible they flummoxed me until I bought them to play with them. :P

            Ah, I want the other CLICK with the sourcing output... and then I can hopefully implement my goal of not supplying voltage everywhere around my oven. Everything is bolted to it via sheetmetal screws and the testing I have done makes me believe the chassis is a viable ground plane.

            Here's my latest simplified drawing, which greatly excites me:

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            It is almost time to start buying things...

            Should I ask about making two CLICKs talk to each other as a continuation here or start a new thread in case other folks stumble upon my question?

            Thanks!
            Chris

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            • #7
              Search. There are already threads for clicks talking.

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