Fault Codes SLC 5/02

gbradley

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Join Date
Apr 2002
Location
Corona, Ca.
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Does anyone know where to find the Fault codes for SLC?


We recently moved a 150 HP Motor about 20 feet from where it was previously.
Nothing has changed in the Ladder file, however, the Processor has faulted three times, since.
I have had to re-download the program to the PLC in order to fix the problem.

It seems to fault when the motor is started.
Fault 002h
Unexpected hardware watchdog timeout or an ASIC reset occurred.

My theory is that the voltage drop when the motor is started is too much for the PLC?
I measured the incoming voltage and it is about 124 Volts, and it drops to about 118 Volts when the motor is started.
This doesn't seem to be too much to me???

I am going to wrap the incoming AC power to the PLC around a toroidal inductor to see if this helps.
Any suggestions??

fc002h.jpg
 
The voltage drop can be a problem easily solved with a small UPS to feed the PLC. Try that to see if the faults go away.

Sid
 
The low voltage will not cause a fault. When a low voltage condition exists, the PLC will stop. When the voltage returns to normal, the PLC should restart on its own. The fault indicates that when the power returns to normal, the memory is corrupt. Does the PLC memory battery need replacing? Check the Battery Low light on the front of the processor. If it is on, replace the battery.
 
I believe you are getting low to high spikes due to 150hP motor startup. That could be related to the distance/mismatched impedence. The best soultion is to use the UPS or get the control voltage from a different source.
 
Thanks! I checked the Website, and couldn't find the fault codes. Should've looked at the help files. RTFM

0002 Unexpected hardware watchdog timeout. This non-user error occurs at power up.

Non-user - a fault caused by various conditions that cease ladder program execution. The user-fault routine is not run when this fault occurs.

I'm still not completely sure why this fault happens.
The battery low LED is not lit.
I guess that I should change out the battery anyhow since it is about three years old.
 
The User Manual for Micrologix page 17-6. (May be same for other AB)
Fault Code 0002H
Advisory Message: Unexpected Reset
Decription: The controller was unexpectedly reset due to a noisy envirnment or internal hardware failure. If the user program downloaded to the controller is valid, the inital data downloaded with the program is used. The retentive lost bit (S:5/8) is set. If the usrer program is valid, the default progrma is loaded.
Recommended Action: Refer to proper grounding
Contact AB if error presists.
 
Why do you think it's voltage, when the error says "Watch dog timer"?

Have you checked the PLC status? When the PLC faults, go to the Processor Status and click on the Scan Times tab

[attachment]

What was the last scan time, and what is the watchdog set to?

It's possible that you have logic that is getting activated when the motor is started, and that logic is increasing your scan time past the watchdog timer amount. That logic could be an infinite loop (JMP/LBL pair), or an incredibly large subroutine, or ???.

status.jpg
 
I would more suspect an electromagnetic pulse.
Try shielding the PLC with a chunk of metal just for a test. Ensure that your panel is closed as well as possible.

Try unhooking any unneeded cables temporarily - programming convenience ports, panelviews, if you can.

I once had a similar fault come up because of (presumably) the external programming port wired in through a 2m cable.

Customer kept accusing me of crashing the program by using one of the newer instructions (the RHC and TDF). When we unhooked the cable the problem reduced frequency from approx once/day to a couple times a month.
 
Allen Nelson said:
Why do you think it's voltage, when the error says "Watch dog timer"?

Exceeding the watchdog timer doesn't wipe out the program like it appears in gbradley's message box.

Wouldn't that be code 0022?

rslfault.gif
 
Last edited:
A reminder, gbradely in his original post
"We recently moved a 150 HP Motor about 20 feet from where it was previously. Nothing has changed in the Ladder file, however, the Processor has faulted three times, since."

I suspect noise caused by distance and 120HP startup inrush current.
 
I don't think I can check the Scan times, S bits, etc. but because the program is not there, I cannot go online.

I'll check out the scan times with the program that is loaded now.
I don't thing that there are any erroneous jump to or huge subroutines.
This program has been running in basically the same form for over three years.
I'll check for any Counters that may be at or near 32767??

It is running now.
We wrapped the incoming 110V AC line to the PLC around a large Inductor.
I've started it probably twenty times, and no fault so far.

Thanks for the suggestions.
 
The problem with the PLC faulting seemed to be the fact that the wires came loose on the NO SHOK sending unit for pressure.

When the machine runs the hydraulic lines flex.
This is usually no problem, but now since they moved the motor and some of the hydraulic lines, they hit the pressure sending unit which shorted the wires and sent 24VDC to the PLC input. This is what was faulting the PLC.

I think that what was killing my program was a direct 24V to the Analog input, but that didn't seem to kill the card, just faulted the processor.
 

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