Good day all. I have a PLC-5 with a PLC5/40E processor. Something happened a couple of days ago that required the operator to reset the machine. Would anyone know if there is an alarm history somewhere that would show what the issue was? Thank you.
No alarm/error history once a fault is cleared, that I know of. Before clearing a fault the status screen will show the error present. There is a "dump file" created if the processor loses its memory which can then be used by AB tech support. See picture below.
a lot depends on what you mean by "the operator had to reset the machine" ...
let's assume (gosh, I hate that word) that you mean a "major fault" occurred and that the operator was able to reset the machine using the processor's keyswitch, etc. ...
you can try this:
go to the Processor Status and then to the Errors tab ... look CAREFULLY at all of the information there ... if you're lucky (I prefer to say "blessed") then you MIGHT find a "left over" error code, etc. that MIGHT prove helpful ...
going further – and answering your specific question ... no, the processor doesn't normally keep a "Fault Log" of recent fault information – but – you CAN program it to store that type of information in a data table ...
the techniques for this are covered near the very end of the book that you got when you took the class ... I can't remember whether we had already covered that part when you had to leave early Friday afternoon – but regardless, look at the very end of the book and you'll find a sample program that makes a data recording each time that an "alarm lamp" comes on ... the data recorded includes:
(1) the year, month, day, hour, minute, and second ...
(2) eight analog inputs ...
(3) four analog outputs ...
(4) sixteen digital inputs ... and
(5) sixteen digital outputs ...
examine the program and you'll see how we used indirect addressing while storing the data – so that we could "march" the data downward through the data tables TWO rows at a time to accommodate more than one occurrence of the lamp "event" ... (the technique is VERY much like the "Rocky Road" exercise that we did earlier – but instead of recording just one analog input, here we're collecting much more data) ...
now then ...
think about the fact that all of the "error codes" and other information on the "Errors" tab in the Processor Status file have ADDRESSES ... these are highlighted in yellow in an attached figure ...
IF (big IF) you're really interested in collecting "MAJOR FAULT" information to help you troubleshoot future problems, then you'll need to set up a new ladder file and enter its number as a Fault Routine as shown ...
the basic idea is that when a major fault occurs, the processor will run through your "Fault Routine" one time – before it shuts down ... so ... you can have the processor collect any information that you're interested in and have it stored in a "fault log" for later analysis ...
I've included a sample "Fault Recorder" routine that might be useful to you ...
DISCLAIMER: I don't have a processor available right now to try this out on, so some "massaging" of the code might be necessary to get it working correctly ... I apologize in advance for any mistakes ...
good luck with your project ...
going one step further ... you might want to discuss with your employer the wisdom of "saving" a few bucks on the hotel and rental car bills by having his employees leave the class early on Friday afternoon ... I'm sure that you're becoming increasingly aware of just how much critical material you missed during those last four hours ...
