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Communication betweem different PLC

Communication betweem different PLC

Communication betweem different PLC


I am involved with a project where information from an existing PLC is to be taken for the purpose of monitoring by a SCADA system. Basic information are indicated below,

Existing PLC - Siemens SIMATIC
Application - Filter control of a water treatment plant

Initially we planed for using Digital IO individually for each status information. However the contractor for the existing works says individual signals can not be provided but communication port can be provided for accessing all status data. (They agreed to use any standard protocol such as profibus, device net or modbus)

We know this is a better solution, but the issue is the existing contractor will not be available when the SCADA contractor begins work.

My question is if there is a way to check, if the status data are actually available. (before the existing contractor leaves the site)

What information should be obtained from the existing contractor so that the SCADA contractor cam proceed with the work.

Or will it be essential for the SCADA contractor to coordinate with the existing contractor.

RE: Communication betweem different PLC

Isn't this something you would, and should, put in an interface control document (ICD)? It should specify what signals are required and on what pins, what protocol, error conditions, etc. The first guy would need to demonstrate that they meet the requirements and the second guy would design from that same ICD and sell off to same.

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RE: Communication betweem different PLC

Hi IRstuff,

Thank you for the reply. I take ICD as a good idea to start with. Regarding the protocol the first guy has agreed to go with any common one, but i will not know the preference of the second guy. However i do not think it will be a serious issue if common one is selected.

I am further thinking the possibility of getting the first guy to make his signals suitable for fiber optic cable.

With that arrangement we can eliminate the need of a PLC (with minimum configuration, only to process the first guy's communication and convert to fiber optic media) and UPS and all that.

But i am not still not sure that the second guy will be able to proceed independently.

best rds

RE: Communication betweem different PLC

What PLC type will the SCADA system be connecting to? That should determine the protocol to be used.

RE: Communication betweem different PLC

Hi djs,

Thank you for the reply.

The SCADA side equipment are not yet decided, and will be decided after tendering.

The target is to finish with the first guy and have everything ready for the second guy to move forward with his work without interaction with the first guy. (but seems difficult?)

Any advice?

RE: Communication betweem different PLC


Thank you for the information. It looks like an emergency exit. Thanks.

RE: Communication betweem different PLC

Perhaps I did not explain my self clearly. To what equipment is the future SCADA going to connect? One item is the PLC in the filter. What other devices will it connect to? This list will determine what drivers will be needed in the SCADA package. Have you selected you SCADA software (Wonderware, iFIX, CiTect etc)?

RE: Communication betweem different PLC

Ok but what make and model are all of the other PLCs?

RE: Communication betweem different PLC

Hi djs,

The make of the other PLC is not decided yet It has to be through competitive bidding and therefore it may be any make. Actually that is the main issue.

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