Muhammad Numan

Delta HMI Communication error

6 posts in this topic

Dear sir,

I am using delta HMI model DOP-B07E411 with Siemens PLC  S7-300, Everything is perfect program is uploading and downloading properly but after some time it will show communication error COM 2 STATION 2: COMMUNICATION ERROR B.

Please suggest a suitable solution.

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http://www.plctalk.net/qanda/showthread.php?t=98877

Since this is not a constant error, I would try the following:
- Ensure that your communication cable separate from your power wiring.
- If the problem still persists, then try lowering the communication baud rate for each device. 

Regards,
Garry 

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Thanks for your response. 

The first option that you suggested, we checked that our communication cable is separate from the power wiring.

and in the second option, we can not change the baud rate of s7-300 PLC.

The baud rate of PLC and HMI is 187.5kbps and will not be changeable.

communication cable connection is:

DOP------MPI

1--------3

6-------8

5-------5

IMG20190703115631.jpg

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What is the distance that you are communicating?
Is it that you do not want to change the baud rate, or cannot change it?
http://www.plctalk.net/qanda/showthread.php?t=53380

One other thing to do is to check the shield of your cable that you are using. It should only be connected to one end. This is usually the PLC side.
Regards,
Garry

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the distance between PLC and HMI is almost 1 meter.

we don't want to change the baud rate, The cable that we are using is shielded.

HMI is communicating with PLC properly but after some time HMI shows  COM 2 STATION 2: COMMUNICATION ERROR B

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it is very unlikely that 1m cable is a problem. is the shed connected anywhere? is there a nearby source of EMI like large PSU or VFD etc.

cannot read resource may also suggest that it is trying to access non-existent variable.

maybe you can you try to go through each screen right after it powers up and see if you get failure sooner. that would suggest that one of objects on that screen is trying to read the troublesome resource. if none of them are causing earlier fault, check if there are global resource (alarm or warning may show up on a banner or popup screen). 

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