Net DDE or OPC?

  • Thread starter Mindaugas Terleckis
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Thread Starter

Mindaugas Terleckis

Have a dillema. Which metod is better for connection of two differend SCADA? Data collection is run on one SCADA and then data must be transferred to another. So, there some way to do that:
1. Use OPC client on receiving SCADA (most expensive and not yet practically tested)
2. Use OPC to DDE converter on receiving SCADA
3. Convert from OPC to DDE on data collecting SCADA ant then send data thru NetDDE to receiving SCADA (cheapest and practically tested).

Is NetDDE well suited for technological data transfer over the network or better to choose OPC?

Donald Pittendrigh

Hi All

Who says that OPC is not tested.....

I don't know what clients you are using but what you propose is standard practice using OPC on 2 major SCADA packages I have worked on.

Why is the OPC "expensive"?

It uses the same hardware that you would likely need for DDE, at least on a Siemens PLC it would, and on a Siemens PLC the OPC server is for free, with the client side it is simply an alternative I/O driver for the SCADA package, like OPCLink in InTouch perhaps.

DDE breaks and doesn't always work quite the same way across vendor platforms, OPC is supposed to eradicate exactly this compatibility issue as it is an vendor independent standard.

Donald Pittendrigh

Yosef Feigenbaum

The real question is are you looking for an inexpensive solution because you need to provide your solution in high volume or are you interested in the best technical solution.

OPC is the best technical solution. Net DDE gets to be problematic when large amounts of data have to be transfered quickly and reliably. I highly recommend going with OPC, the newer/more robust technology.

Good Luck,
(8{)} ( .)
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Frank Iwanitz

try OPC. I do not know whether Microsoft with XP or even Longhorn still supports NetDDE.

OPC is the only way to go. DDE is a bad memory most of us would like to forget.

I have successfully implemented a SCADA to SCADA solution using OPC to transfer data from Intellution iFIX. to Wonderware Intouch (This was the customer’s requirement, not my idea) The system works extremely well. One caveat, not all OPC servers are created equal, but I have had very good luck with OPC servers from Rockwell, Intellution and Wonderware. There are a ton of great utilities and support for OPC to. One utility I have found indispensable is OPC Explorer from Matrikon.