CompactLogix Program Curruption

[sruda]

I got a used 1769-L35E Ser. A from our customer to use on our new machine. I had updated the firmware to the latest version and started working with the controller.

Things went well for a while, then all of a sudden bits in the program would randomlly unlatch in the controller stopping the program. I reviewed the code many times and saw nothing that would unlatch these bits. I power cycled and re-downloaded the program and everything works great again. There was nothing changed in the program. It will run fine for a few hours then this will happen again.

I have tried reloading the firmware and upgraded again to 20.14. Still having the same issue. when this happens there are no major or minor faults in the controller and a power cycle alone will not recover the PLC. The program must be re-downloaded before it will recover.

Any thoughts? Sure is throwing me for a loop.

Thanks
Sayyed

 

[bkottaras]

I got a used 1769-L35E Ser. A from our customer to use on our new machine. I had updated the firmware to the latest version and started working with the controller.

Things went well for a while, then all of a sudden bits in the program would randomlly unlatch in the controller stopping the program. I reviewed the code many times and saw nothing that would unlatch these bits. I power cycled and re-downloaded the program and everything works great again. There was nothing changed in the program. It will run fine for a few hours then this will happen again.

I have tried reloading the firmware and upgraded again to 20.14. Still having the same issue. when this happens there are no major or minor faults in the controller and a power cycle alone will not recover the PLC. The program must be re-downloaded before it will recover.

Any thoughts? Sure is throwing me for a loop.

Thanks
Sayyed

Do you have any Power spikes and such on site?
I've had quite a few L35's losing/corrupting their program during such an event.
Try a surge filter feeding the L35(corcom or similar).
It cured the corruption/re-load in my cases.

 

[Ken Roach]

The plastic-cased CompactLogix is notably more susceptible to voltage spikes that corrupt the memory than the steel-framed PLC-5 or ControlLogix are.

But "turning random bits off" is not the symptom.

One of the most important functions of any PLC operating system, including the CompactLogix, is the prevention of unintentional operation. The controller checks the program for a checksum every cycle, to prevent any memory error from causing unintended operation.

Nothing is "impossible"; we live in a universe of randomness and near-infinite possibilities. But a CompactLogix "randomly turning off bits" without faulting the controller is as unlikely as me waking up tomorrow with purple fur.

It's possible that actual hardware input points are being mis-reported to the controller or have a floating ground or an intermittent connection, or that an HMI or messaging or indirect-addressed logic is somehow commanding data to states that you don't expect. But it is almost impossible that the controller itself experiencing "corrupted" memory without faulting.

 

[sruda]

I don't expect that there are any power spikes. This is an assembly machine. It has its own 600V to 208Y transformer. The all equipment on the machine is 120V and mainly pneumatic. The only heavy electrical load is vibration feeders.

I will try the power surge filter and see what happens.

RA support has suggested I save my file as L5K and reload into RSLogix and controller and will be trying this as well.

Just dont know why it would work for so long and then this would randomly happen. If this were a floating ground issue or a bad input connection this would happen all the time and reloading the program would not correct the issue.

 

[sruda]

Fixed!

Thanks bkottaras didn't think it was a noise issue at all. But I ordered a EMC filter and installed it since it was only $16. It fixed the issue so far, no re occurance since last night. Seems the vibration feeders are the source of all my noise.

Vary unsettling that the controller does not throw a fault in this case. But feel much better that it was not a coding issue like RA said...would have made me feel a little inadiquate after 8 years of PLC programming lol