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P2k Analog Input Issues

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  • xyouman
    started a topic P2k Analog Input Issues

    P2k Analog Input Issues

    Short disclaimer, I've only been working with PLC's for the past few months so I am by no means an expert. That said, I have a P2k with a 7-slot base as shown below. There is a lot going on with this setup so I'll try to keep it simple; if more info is needed just let me know.

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    I'm using the PLC as the brain for a tester of ECU's that my company designs. I've got a 12V power supply, a 24V power supply, a couple boards simulating loads for specific components the ECU's see and an HMI; everything works great except some of the analog inputs (on the P2-16AD-2).

    I am using it to measure five different voltage signals and only three of them work. I have tried a few things to determine what it could be but all I have determined is that I have no idea what's going on; I have tried switching to different channels (including ones I know work) to see if its just a faulty channel, I have tried switching out the module entirely to see if its just a faulty module, and I have tried switching them with one of the three working channels out of curiosity. I've had no luck with any of these methods.

    The first signal that's failing starts at around 9.5V and drops to around 5V in certain subroutines. I've measured the current through the module and observed the voltage with a multimeter and an oscilloscope to verify this is actually happening and that it's happening within the safe parameters for the module. When the subroutines are called, the signal seems to freeze and stay at 9.5V (about 61000 counts).

    The second signal is similar. It goes from 0V to 8V and 9V (in separate subroutines), however, I don't see any change. I have measured this signal the same as the first with the same results. Unfortunately, I can't tell if its freezing or not for this one since it starts at 0V.

    Lastly I'll throw in some other info that may be pertinent; I'm sure I'll forget something though. I have double and triple checked that I am using the correct ports for the specified channels, I have ensured that the wires have good connections all the way through to the PLC, and I have made sure all my commons are tied together where appropriate. Just to reiderate, everything else on the machine works perfectly.

    Has anyone else ever seen this "freezing" on their analog inputs?

    Thanks in advance.

  • LWgreys
    replied
    Hey, could you send me a wiring diagram of your setup by email. I'll be glad to help!

    Leave a comment:


  • xyouman
    replied
    Yeah, I get the feeling that's whats going to have to happen. I'll talk to my bosses about it. Until next week, thanks for your help.

    Leave a comment:


  • RogerR
    replied
    Probably need to view the program or electrical schematics to gain any new insight.

    Leave a comment:


  • xyouman
    replied
    All the commons are correctly bonded. Took all day but I got it.

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  • xyouman
    replied
    I'll check all the commons right now and get back to you.

    Leave a comment:


  • RogerR
    replied
    Does the circuit break the common instead of the +dc voltage anywhere?

    Checking to see if the commons are all bonded completely.
    With the unit running and changing... If you check from one common point to each other common point in the different ends of the circuit with a volt meter on low range, is there a voltage?
    If there is, then maybe there is some kind of break or resistance from one common to another.

    Leave a comment:


  • xyouman
    replied
    No luck. I tested both channels that aren't working with analog inputs and the Data View "Toggle IO View". The channels are working fine; its something else. Could a specific signal cause this freezing? Or could a signal be ignored by the hardware somehow?

    Leave a comment:


  • xyouman
    replied
    I've switched the channels several times to check if it was any one channel. They all work, they just don't/can't measure these two signals.
    I'll give it a shot though; I'm at a complete loss as to why this doesn't work.

    Leave a comment:


  • MikeN
    replied
    Could you wire the analog outputs into your analog inputs, and then adjust the output level through data view in the program. It wont even require any ladder code to test, just the tags in a data view. Adjust the values for the output and see if the input it is wired to changes to match. That will let you know if the inputs or outputs are defective since nothing else will be wired in and no code in involved at all.

    Leave a comment:


  • xyouman
    replied
    Sorry I didn't see that comment until now since its on a new page...

    Do you mean an electrical print of the RPM simulator board or of the whole thing? I don't think I'd be able to post that online flat out; I'll find out.

    Leave a comment:


  • RogerR
    replied
    Hmmm..... Do you have an electrical print and a copy of the program to post?
    Someone here may be able to see what is happening.

    Leave a comment:


  • xyouman
    replied
    No the digital output module only sends on/off signals to a separate board. The board has a safe separation between the signals and the actual operation the board is used for (RPM simulation).

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  • RogerR
    replied
    Is the power to the digital output modules driving relays?

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  • xyouman
    replied
    The 24VDC power supply only powers the analog input, analog output, and the digital output modules. Is that enough separation?

    Leave a comment:

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