problem in plc with data loss

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Thread Starter

Devesh Yadav

I'm facing a problem with cimplicity hmi. Sometimes there is no communication between plc and hmi and all the data is lost. it happens for a very short duration like 6-8 secs. sometime upto 20 secs. and it is not sure when would it occur. i have checked up everything and found it ok. can anybody tell me what is the problem and how it can be rectified?
 
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Robert Willis

It would help if you would provide some detailed information on the manfacture of the HMI and PLC in addition the the network layout being used.

The first thing that I would is look at the communication data logger that may be included in the HMI package to see if it will give you any error codes that may affect the communication.

Regards
Robert Willis
Square D Company
Houston, Texas




> I'm facing a problem with cimplicity hmi. Sometimes there is no communication between plc and hmi and all the data is lost. it happens for a very short duration like 6-8 secs. sometime upto 20 secs. and it is not sure when would it occur. i have checked up everything and found it ok. can anybody tell me what is the problem and how it can be rectified? <

 
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Jayaharan C J

Dear Devesh Yadav,

The problem you are facing I beleive has nothing to do with the PLC. The problem purely lies on the HMI /SCADA side and in the driver software in particular.

So try to change/increase the "Reply timeout" which specifies how long the I/O driver waits for a response from the PLC

Also change the number of "retries" which is the total number of messages re-sent to the PLC.

The resons for the irregular response from the PLc may be
1.Checksum errors from communication line interference.
2.PLC may be busy with other task

So if you try increasing the timeout and the number of retries,your communication problem will be solved.

Best regards

Jayaharan C J

 
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Vladimir E. Zyubin

Hello List,

LM> From: Devesh Yadav <[email protected]>

LM> I'm facing a problem with cimplicity hmi. Sometimes there is no
LM> communication between plc and hmi and all the data is lost. it happens for
LM> a very short duration like 6-8 secs. sometime upto 20 secs. and it is not
LM> sure when would it occur.i have checked up everything and found it ok.can
LM> anybody tell me what is the problem and how it can be rectified?

Just a supposition...

The cause could be in a concealed restart of the plc. Some systems have this feature... and the restart (because of watch-dog, etc.) is visible for privileged user only... In normal mode, the plc can restart without any message about it...
just a delay during communication is originated from the event.

Again, just a supposition.

--
Best regards,
Vladimir mailto:[email protected]
 
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Devesh,

I have seen communication drop outs caused by many things. You do not mention the communication driver and/or platform. (ethernet, serial, DH+) Is the communication port dedicated to the HMI? Because I am working in a regulated environment we can't tolerate data loss and create architectures that prohibit this from occurring. We typically create a handshaking routine for data and do not delete the data in a PLC buffer until the data has been successfully stored in a database. We use a circular buffer in the PLC which can sustain production for a
short time without the PC interface and store data on the PC locally if the network becomes unavailable. All levels re-connect and transfer data automatically. Even the problem described below could be corrected by this architecture. I assume the machine is not re-booting as your process would also stop.
I have seen 3rd party drivers cause this because of communication management. RSLinx for example has built in queueing of transmission
requests that make life easier, but you need to deal with their product activation. Talking to a PLC with programming tools causes drop outs from ethernet lines because the processor is so busy. If you can supply more info, I may be able to lend some more insight.

Dale
 
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Devesh Yadav

Thanx Robert ,
The HMI i'm using is Cimplicity and GE Fanuc PLC.
Sometimes i use to get the message 'Pipeline Busy at instance'.
Kindly suggest how could i rectify it.
 
I have the same problem with Simatic CPU 316-2DP and WinCC. Nobody knows what the problem is, even Siemens!!

Regards
MI

 
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Eduardo Manuel C. Cipriano

hi

I guess you better use other much better systems like Yokogawa or Allen Bradley Systems
 
hi devesh

first up all i want to know the communication card
that you are using? it's specification
what is the capacity of pc on which you are running the cimplicity software

regards
kaustubh
 
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