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  • Newbie Sink I/O Question

    I'm starting to spec out a PLC, and have a question about best practices for sinking outputs. I will have 12 and 24 and even a handful of 5v voltage sources that I'll need to actuate. The spec sheet says that they can accept 3.3-24v. Because they are sinking output, the load is being supplied via the device, and the module is only providing the path to 0v so conceivably each could be a different voltage level as long as it's within range. What's considered best practice? Should voltages be grouped via module? Via common groups? Obviously I can always use relays, but most are very lower power devices and seems redundant if it's not needed.



  • #2
    Mixing them would probably work OK electrically.

    For ease of troubleshooting, I would try to keep them in groups as much as possible.
    Most of the output modules have four outputs to a common point.
    Keep the voltages separate to each group unless there are no extra outputs.

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    • #3
      With the P2k I had trouble having a bank of outputs be 12v sinking while the rest were 24v sinking. It should be possible, and I have done it successfully on the P3k, but for some reason I never got it working with a P2k. Instead I had to use relays to interface the 24v PLC outputs to the 12v IO I was using. Thankfully I only needed 3 outputs so it wasnt that big of a deal, but just wanted you to be aware that you too may have trouble getting it all to work.


      That said, look on page 2 of this PDF to see how it says to do multiple power supply wiring to an output module:
      https://cdn.automationdirect.com/sta...s/p208td1s.pdf
      Last edited by MikeN; 10-02-2018, 09:15 AM.

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      • #4
        Originally posted by MikeN View Post
        That said, look on page 2 of this PDF to see how it says to do multiple power supply wiring to an output module:
        https://cdn.automationdirect.com/sta...s/p208td1s.pdf
        The diagram reads like you need the higher voltage to get the outputs to change state.
        Why worry? If you've done the best you can, worrying won't make it any better

        - Walt Disney

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        • #5
          Originally posted by Todd Dice View Post

          The diagram reads like you need the higher voltage to get the outputs to change state.
          Maybe you do when doing dual supply.
          I have used those modules with 5v across the whole thing as outputs to stepper drives and it works fine. I just havent been successful doing dual voltages on the same card yet.
          Then again, even though I tried two different P2k modules and both did not work in dual voltages, perhaps the problem wasnt with the P2k but rather with both of the GS1s I was using? IDK how that would be because both GS1's had the same behavior of not working with the P2k I was wiring in dual voltage, but I have used a GS1 and a GS3 wired for dual voltage on a P3k just fine. Weird.
          Last edited by MikeN; 10-02-2018, 11:08 AM.

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          • #6
            Thanks for the advice. I'm actually planning on using the P1K. It seems as though pin 18 is powering the taking care of the power inside the module, while pins 1 and 10 are the commons for the actual loads.

            Sounds like it might work, might not. I'm kind of on the edge of what the P1K can offer from a module number wise. Might go back to the drawing board and see if I can consolidate some of my IO's or just upgrade the to P2K. The P2K is $600 more for the same current configuration of the P1K *gulp*

            https://cdn.automationdirect.com/sta...s/P1-15TD1.pdf

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            • #7
              Originally posted by Todd Dice View Post

              The diagram reads like you need the higher voltage to get the outputs to change state.
              The way I interpret that diagram is that you just need to ensure both power supply negative terminals are tied together.

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