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Thread: Clearing Faults

  1. #1
    Member pico-dc's Avatar
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    Clearing Faults

    Hello,

    I'm trying to clear faults on an Allen Bradley ControlLogix PLC without using the RUN/REM/PROG switch or through the Controller properties in Studio 5000.

    Is there a way to clear faults using a bit programmatically, like on startup?

    Thanks!

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    Senior Member jamesonline's Avatar
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    Quote Originally Posted by pico-dc View Post
    Hello,

    I'm trying to clear faults on an Allen Bradley ControlLogix PLC without using the RUN/REM/PROG switch or through the Controller properties in Studio 5000.

    Is there a way to clear faults using a bit programmatically, like on startup?

    Thanks!
    I utilize a controller fault handler routine to capture a few common faults and reset them, mostly the indirect address pointer out of range fault caused by a typo. Using GSV to get fault code and seeing if it is the code number in the manual and SSV instructon to reset it. Also put in a counter on the rung so I know it's being activated when troubleshooting logic as there is no other notification that it's running.

    The PLC logic will be scanning your program loop continuously until a fault is found, then call the subroutine fault handler. If that doesn't rectify the problem, the controller fault handler program will scan and if that doesn't fix the problem the controller will give up and toss out the key switch reset requirement to clear the fault. Once it hits that stage there isn't anything that can be done.

    The big key point here should be understanding what is the reason why your fault is triggered and rectifying the problem. Sure you can keep clearing the fault with the above logic but that's going to just mask the root cause.

  3. The Following User Says Thank You to jamesonline For This Useful Post:

    Shawn Tierney (03-25-2019)

  4. #3
    Administrator Shawn Tierney's Avatar
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    Good afternoon @pico-dc,

    @jamesonline really nailed it with his reply about using a Fault Routine (thanks James!)

    Keep in mind if you just clear the error without understanding what caused it, you also won't likely understand all the ramifications of the fault, including any "garbage" data left over from the fault.

    Good luck!

    Shawn Tierney,
    Instructor at The Automation School
    Looking for affordable automation training? If you are, check out my courses at TheAutomationSchool.com!

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