PLC Losing Program

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Thread Starter

Atom

I have a customer with an AB CompactLogix processor that occasionally lost it's program and they have to re-download to it. I have talked with AB about the issue and the main reason they thought it would do that is from line noise. We have installed a surge suppressor and the problem still exists. The plant has a bunch of the same processors all running from the same main power and none of the other ones have had this issue.

If anyone knows of anything else that might be causing this or has run into this problem, any help would be appreciated.

Thanks!
 
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Eduardo Manuel C. Cipriano

Hello,

We have the same problem in some of our customer here in the Philippines, but this happens on SLC and PLC5,

We usually check if the PLC is incorporated in the same panel with a Frequency Drives, please make sure that your PLC is isolated from any VFD, also grounding system is a factor make sure that your power ground is different with your earth ground, and finally if there is a possibility of installing a memory card we usually encourage to install an EEPROM.

Eduardo Manuel C. Cipriano
Mheco Inc.
Systems Integration Manager
812 Herrera Tower, Va Rufino corner Valero St.
Salcedo Village Makati City
Philippines
Rockwell Authorized System Integrator
Tel: (632) 8448901
Fax: (632) 8451535
Email [email protected]
Mobile : +63919 4211737
 
W

Wayne Shimanis

Atom:

I have had several situation with PLC's losing programs. Surge suppressors alone usually do not solve the problem, unless the surge suppressor also incorporates EMI\RFI filtering. With faster processor and switch mode power supply speeds, ground transients will also effect the operation of these devices. Ground transients can cause malfunction or out right damage to sensitive components. Check out the IL-120 series and IL-GTT line of products offered by Vortex Technologies Inc. (vortextek.com). These products have been successful in fixing the type of problem you describe.

Wayne Shimanis
 
Make sure there is a good ground.

Also make sure there is no potential between neutral and ground. I had a neutral on the 120 once that wasn't tied to ground and would fault the processor and erase the program. If this isn't the problem then replace the unit.
 
More often than not we have found this to be grounding related issues. I would check the ground and then double check it.

Eddie
 
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Eddie Willers

I've seen CompactLogix go into a hard fault if the backplane latches aren't all snapped into place.

I've also seen them lose the program if they are subjected to short (under 1/2 second) power interruptions; I heard the memory checksum routine can get messed up if power is dropped during that routine.

The input power isn't the only place noise can get into a controller; Make sure suppressors are installed on relay outputs and check serial links for noise too.
 
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William Hinton Sr. Electrical Engineer @

We have had some of the same problems:
Our backplane dip switch was set to transfer EPROM to RAM on power up, we changed it to start back where it left off in battery backed RAM.

Standard TVSS units do little or nothing for noise so we solved our noise issues by installing a Phaseback EMTVSS. One per power system not one per controller, get info @
http://www.applied-energy.us

I hope this helps.
 
J

Jasmin Ouellet

check with your local A-B distributor: there has been a lot of PSA lately (Product Safety Alert).

these notices are sent to distributor (and some customer) when a potentialy dangerous situation exist. They DO exist but most of the time, distributor won't do much about telling their customer!

also, it would have been a good idea that you mention what version you are at: very often, some of these small "bugs" (small according to A-B) are "silently" fixed with new release!

regards,

Jasmin Ouellet
[email protected]
(working for an A-B distributor)
 
B
Atom - Check to ensure that all signal ground wires in the system are attached to a single, clean well designed ground point.

If you need more grounding hints contact me off line at [email protected]

Bob
 
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I've seen CompactLogix go into a hard fault if the backplane latches aren't all snapped into place.

I've also seen them lose the program if they are subjected to short (under 1/2 second) power interruptions; I heard the memory checksum routine can get messed up if power is dropped during that routine.

I seem to recall this is a known issue with CLX processors and can be fixed with a later firmware release.

The input power isn't the only place noise can get into a controller; Make sure suppressors are installed on relay outputs and check serial links for noise too.

Bob Peterson
 
I read the other replies, they had already discussed the "Ground" & "Noise: issues. But don't forget, every PLC runs the program by the RAM, if the PLC has the problem on providing the backup power to the RAM and that PLC cannot/did not install any nonvolatile memory. All the data on the RAM will be lost.
UPS is one of the solution. Maintain to provide the main power steadily is very important.

Regards,

Alex Lam
 
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