slc 500, a rack data error is detected check slot 2.

[robleamy]

whats up guys first post here been having trouble with a plc out in the field that keeps faulting with "a rack data error is detected check slot 2" it has been happening since its instalation about 2 years ago weve even gone as far as replacing the plc entirely and still get the same fault. Funny thing is after replacing the plc it didnt fault for about 6 months or so now its back to its normal faulting and its quite irritating.

 

[jkerekes]

Only 1 rack? What module is in slot 2? Did you replace that? Clean the contacts of module 2?

 

[James Mcquade]

two things come to mind.

#1. is this a speciality module? if so, set the status bits to fault over ride at power up. some modules take longer to initialize at power up than others.

#2. have you replaced the rack? we had the same fault last year and replaced the rack. hasn't faulted since.

regards,
james

 

[OkiePC]

Grounding. You replaced the rack, and tidied up some grounding, but something is puttin noise on teh back plane. This is assuming you replaced all cards when you said "entirely". A severe static, backplane ground noise, or card problem can cause the SLC to misidentify a slot number too. It can be any card on the backplane bus. Surge protection for inductive loads is also wise to keep noise from appearing on the backplane.

There is a story here about one of mine that ended up being traced to a solenoid with a failed MOV on a relay output module spiking the backplane. It weeks to find being so sporadic a problem.

 

[robleamy]

Thanks for the quick replies guys! I was looking at the grouding earlier and it wasnt to pretty, so im heading back out tomorrow to try to clean it up the only grounding the plc has is one 10 guage cable that ties in with a lightning arrestor and then goes to the ground bus in the breaker pannel. the tabs are on the painted surface and please explain the back plain stuff in some more detail, im not a programmer or electrician. also we do have a ice cube relay that chatters due to electrical not programming. this is all new to me so all the help is great thanks so much!

 

[OkiePC]

I was looking at the grouding earlier and it wasnt to pretty, so im heading back out tomorrow to try to clean it up the only grounding the plc has is one 10 guage cable that ties in with a lightning arrestor and then goes to the ground bus in the breaker pannel.

I am no expert with lightning arrestors, but I would expect that it's ground be bonded to a main building ground ... not sure how near to that ground I would want a PLC power supply ground tied in.

the tabs are on the painted surface and please explain the back plain stuff in some more detail, im not a programmer or electrician. also we do have a ice cube relay that chatters due to electrical not programming. this is all new to me so all the help is great thanks so much!

Big (10 or 12 awg) Green ground wire from the power supply ground terminal to the first chassis mounting screw on the bottom. Bust the paint off of the backplane under that mounting tab. Some masking tape and a dremel flat disc do a nice job, a hot flat tip screwdriver is sometimes good enough to get bare metal. I use a bare ring terminal under that screw, I want this wire permanent, and hard to take off. The ground terminal should also be connected to the system ground with another separate green wire.

And make sure the power source grounding is done right. Calling an industrial electrician for on site advise might be money well spent here.