SLC150 power up cpu fault

[mark@snappy]

We have a machine which uses a an a SLC150 to control functions. It has a fresh battery to back-up the memory, however anytime equipment power gets shut down, the "red" cpu fault LED goes on
and plc drops out of the run mode.

Right now PLC gets back into run mode by hooking up lap-top
and putting PLC back into run mode.

Is there a eprom setting that needs to get changed and some additional lines entered into our machine control ladder to stop
the PLC from faulting out?

I am sure there is a straight forward solution to this, but at the present time I have not been able to solve this issue.

Please advise.

Thank you for your attention, understading and your time.

Respectfully,
mark@snappy

 

[grover1]

Mark,

You might try putting an oscope or data analyzer on the PLC input power line to see if there are any spikes occurring at power shut down. The collapsing fields of solenoids can induce some wicked counter-emf. Perhaps you have some open snubbers or supression diodes somewhere. Is the SLC a DC or AC model?

Congratulations on having a SLC-150! Oh-boy. (They're actually quite reliable).

Grover

 

[jrwb4gbm]

Workaround

This is not an answer to your question, just a suggestion. I would use a 120 VAC UPS (fairly large capacity) to keep power on just the PLC during weekend shutdowns and during other minor power blips. I use a MCR relay to shutdown all the rest of the machine. This must be reset after any power interruption or emergency stop.

 

[mark@snappy]

slc150 cpu fault

Dear Gents,
Thanks for the response and your comments recommendations.
Our SLC150 is an AC unit.
We are checking out the snubbers/suppressors now and will advise.

Thanks again!

 

[Sheldn]

The SLC 500 has an Eprom that you can burn the program. It has been at least 15 years, but I recall using the PLC programming software to burn an EPROM installed in the SLC itself. I don't recall what specific setting you use to tell it to load from EPROM on corrupt or missing memory. All settings were set using the programming software.

Good luck.

 

[Lancie1]

Mark,
Some quick suggestions:

1. DO add a small UPS (Uninterruptible Power Supply) in the bottom of the PLC cabinet. Plug the PLC into the UPS, and the UPS into the normal equipment power. Keep the PLC hot all the time. $150 could solve all your problems.

2. DO review the SLC150 program for errors that could cause a fault upon equipment shutdown. Division-by-zero is far too common. If some memory value goes to zero at shutdown, dividing by zero can definitely cause a fault.

 

[grover1]

Mark,


Is this a new fault?

Grover

 

[Scooter]

Are you having to re-load the program or just put it back in run?
I can assume that the Auto/Man switch is in Auto?

 

[parky]

Not sure about a 150, but had a simular problem on a 500, it would go into stop (only if powered down & not every time), fault showed up a NVRAM corrupt, now we have a dozen of these on site & all very simular but this one is the olny one that fails, I changed the processor & it still failed.
I then replaced the whole shooting match & it still failed?
I could not see anything in the ladder that would cause it, in the end I fitted an EEPROM & since then have not had a single problem.

 

[AndrewB]

im assuming its only a baby application being a 150

why not just change it to a micrologix 1000 (or something else)
prob cheaper in the long run than chasing a tricky problem

 

[grover1]

AndrewB,

That would probably work in many cases but not all. If the machine is used in the bio/pharma/food industry, the entire machine would need to be re-validated. It is not a trivial process and is far more than a functional check. Mark may be stuck with fixing the 150 until the powers-that-be decide it can be changed.

Otherwise, I agree, a shiny new ML should do the trick!

Grover

 

[AndrewB]

fair call, I Overlooked that scenario.

 

[Steve B]

SLC fault

Are you sure the battery is good.We have a lot of SLC 150's out there,in some of them the internal lithium batteries are failig now and I have installed the xtra add on battery to make up for it.
I would say if you are still having a problem,even with a NEW battery the PLC is gone.Get a rebuilt one on the internet,they don't make them anymore.