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Bus Fault in PLC

09/06/2008 7:58 PM

Hi,

Momentary bus faults happening in simatic S7 300 module. Kindly, explain me what is Bus fault? & how can it be avoided?

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#1

Re: Bus fault in PLC

09/07/2008 12:01 AM

Hello Lspraba

You do not list your Location or Country. (You may do that in your Member Profile, and it will auto-update through all your Topics and Posts)

Best idea would be to go to: http://www.automation.siemens.com/partner/guiGeoSearch.asp?regid=DEF〈=en&reduce=prodid516999&comptcID=v

Navigate there to your Local Siemens Webpage, and contact them.

They are a responsible Company, and should be delighted to assist you.

Kind Regards....

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#2
In reply to #1

Re: Bus fault in PLC

09/07/2008 1:01 AM

I don't know much about this brand of PLC.

The voltage switched through your output points should be supplied for a different source.

The voltage from input devices should have a path to neutral or common that is isolated from the backplane.

I would check your power supply to the processor and back plane first. I would power it off and re-seat the processor and all the I/O cards.

If it checks out, I would remove any voltage to all the I/O and try that(one at a time if possible)

If the problem remains--Check the backplane and processor module.

Again--do one thing at a time if possible.

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#3
In reply to #2

Re: Bus fault in PLC

09/07/2008 2:10 AM

typo-

The voltage switched through your output points should be supplied for a different source.

From a different source--isolated.

sorry

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#4

Re: Bus Fault in PLC

09/07/2008 3:25 PM

Hello Lsprabra,

Good to make your aquaintence.

Bus faults can be generated/caused by many different failures/issues.

First; you need to interrogate the PLC "Status Bit Table" in order to identify the type of fault. The Siemens programming instructions documentation details the procedure required to access the fault table and how to correctly identify the fault identity.

Second; Once you have identified the type of fault, it is simply a matter of separating and testing until you can locate the "root cause" of the fault. Caution: There may be more than one issue causing the fault so be sure and test for all listed "cause of fault" items.

Intermittent Bus Faults usually are a result of Bus Communications Clock signal failure. Many times this is due to incorrect installation, component imcompatibility, or configuration errors of an individual (usually third party vendor supplied) PLC rack module. Important System Configuration settings are such as: System Interrupt Schedule (type & priority assignment), Protocol Type Selection, Parity (odd - even), Start and/or Stop bit(s), Baud Rate (9600, 22k, 56k, etc), proper chassis grounding, and rated device operating voltage level as well as analog "sink or source" capabilities. It is of the utmost importance that all of the components resident in the PLC rack and any components attached to the PLC, are configured exactly as per the PLC manufacturer requirements.

I recommend that you thoroughly access, review, and document the configuration of all the PLC components. If you cannot understand how to do this and/or do not find anything obviously awry, contact Siemens Technical Support for help.

Good Luck,

Jim

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#5
In reply to #4

Re: Bus Fault in PLC

09/07/2008 5:27 PM

Hello SHOCKISCAN

from me,

Kind Regards....

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#6
In reply to #4

Re: Bus Fault in PLC

09/07/2008 5:56 PM

Thank you Mr.Jim.

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#7

Re: Bus Fault in PLC

09/09/2008 1:48 AM

S7-300 module.

Ok, I'm guessing your using the MPI/DP or the Profi-Bus connection?

You didn't give specifics of your S7-300 model. (the model number is laser engraved on the side of the CPU module, there is no I/O directly on the CPU, it utilizes "Distributed IO" thru the MPI/DP Interface.

Have you completely checked your profi-bus lines for breakages, moving cables in ladder trunking can give problems, these are the bus faults I have had in the past, also loose or impropper connectivity on your end points, another could be a not quite "homed" trmination switch (easily to switch if the plug is removed and reseated wrongly)

Intermittant "BUS Error" can be a real pain in the butt to work out, we have actually stripped the whole profi-bus out of a system to locate that, also switching each terminator on and communication to that extent to find the problem.

You may also have a intermittant power supply problem to one of your remote modules, if there is no power, comms with that module will give a problem, and a Bus error.

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#8
In reply to #7

Re: Bus Fault in PLC

09/09/2008 3:54 AM

Wow--I am hitting the books.

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#9
In reply to #8

Re: Bus Fault in PLC

09/09/2008 7:45 PM

There are books on this?

My boss didn't give me any books, just told to find the problem ;o(

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#10
In reply to #9

Re: Bus Fault in PLC

09/10/2008 3:51 AM

Are you kidding?

There are NO BOOKS?

Then screw it then I'm hitting the bottle.

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#11
In reply to #10

Re: Bus Fault in PLC

09/10/2008 1:24 PM

Hello Kilgore Trout

That's what the ship does, at the naming ceremony.

Kind Regards....

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