Siemens S7 OPC Connection - basic info needed

DRL

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Join Date
Sep 2006
Location
Bergen
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Hello guys

I am a novice programmer (actually just an electrical engineer who got the added programming responsibility as noone else wanted it), and I am in need of some basic information which I hope some of you can help me with. I will try to be brief but consise :D

The situation:
Our company engineers and manufactures firewater pump modules for offshore use, and as such our control systems was pretty straightforward for a long time; mainly a handful of digital signals and a couple analogue signals. The only connections to the "outside" systems was hardwired digital signals (start/stop, on/off, normal/alarm etc). They are currently increasing in complexity however, and we recently made the switch to a Siemens S7 plc system.
Our standard setup is now a 315-2DP cpu (using MPI output to Siemens HMI panel, and ProfiBus output to a distributed IO), 1x CP-341 (serial link to diesel ECU), 2x Digital In, 2x Digital Out, 1x Analogue In, 1x Analogue Out.

As an option we have also provided some packages with an extra CP module, using either Profibus or ModBus to transfer alarm status and analogue transmitter values to the platform control system.

We recently acquired a project for a customer who wants alarm/status information sent to their platform control system via Ethernet OPC. They are using a PCS7 system.

The question:
I must admit I've never even heard of OPC, and the little I could find from a quick browse on the net didn't make things all too clear for me. Do you guys know of any good sites explaining OPC, and maybe even how to set it up with our S7-315-2DP cpu and what extra module we would need for this?
I was also concerned that adding an extra CP module for this OPC connection might put too much strain on the cpu we are using, since we would have connection to HMI + distributed IO + diesel ECU + Ethernet OPC.. Can we still use the good old cpu or would we need to upgrade to another type?

This connection is just for transmitting information from our system to the platform system, as our package must be able to run independantly of what happens to the rest (our firefighting system should be the last to go down hopefully :rolleyes: ).

Thanks in advance for any replies.


EDIT: I forgot to add that all programming has been made using CFC charts and SCL blocks.
 
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Welcome

You should take a look at Siemens tech support pages. They have some examples that could get you started. I don't know much about the systems you are using but we do have some members that could help I think.

Here is a link to a search I did

http://support.automation.siemens.com/US/llisapi.dll?func=cslib.csinfo2&siteid=cseus&lang=en&aktprim=99&startNode=4000024&nodeid0=4000024

and here is a link to tech support page

http://support.automation.siemens.com/US/llisapi.dll?func=cslib.csinfo&aktprim=0&siteid=cseus&lang=en&nodeid0=4000024&siteid=cseus&extranet=standard
 
Hi DRL.

As the customer has specified Ethernet then you simply have to add an Ethernet CP to the existing S7-300 rack. I understand that you dont have anything to do on the PCS7 side. OPC is a standard for setting up communication connections from PCs to PLCs for example. That means you can forget about OPC for now. It is the other guys who have to worry about setting up OPC.
A CP343-1 LEAN is enough, it is half price of a normal CP343-1.

edit: About the need for exhanging the CPU. You can probably keep the old CPU if the additional data exchange isnt very much.
How much data is it ? And how often do you need to send it ?
 
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Sorry for the late reply (businesstrips taking longer than planned ftl), and thanks for your answers.

Seems I thought this OPC stuff was more advanced and difficult to set up than it actually is - specially since I don't have anything to do with the PCS7 system.

The data we are sending to their main system is just digital status and alarm signals and a few analogue values from the transmitters, nothing major. It's just made available for display on their scada system. A quick estimate would be 6 bytes for the digital status/alarms and 10 integers for the analogue values. How often this is transmitted I'm not sure, what are the options here? I have only set up serial links before where our system got regularly polled to send the data, but maybe with ethernet connection you can have an active slave sending data on change? That should reduce the workload alot. This communication isn't time-critical in any way, it is mostly for information purposes to the platform system. The main logic and control is all done locally on our own system.

Anyway, thanks for your help so far, I will probably be back with more specific questions once I get my hands on the hardware and programming software (y)
 

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