RSLinx, Excel, & OPC?

[Duranthas]

Thanks to quite a bit of searching and the sample VB/VBA various members have posted I have figured out how to write macros in Excel and an ugly VB program to read/write to my processors with DDE. After reading around I hear quite a bit of discussion about how OPC is better than DDE, but don't see much if any examples of how to do this. Is OPC more complicated and therefore not really worth the hassle when mainly dealing with Excel? I've found various programs one can purchase which do this but not much "code". Eventually I'd like to write a simple program in VB that pulls production/downtime and a few other tidbits and throws them into an Excel file. The reason I'm becoming more interested in OPC than DDE is because to my understanding DDE is losing its support in newer versions of VB.

Thanks for any input

 

[adrielmichaud]

If your OPC Server also supports DDE, DDE is usable "out of the box", no VB required. Ie: you can start calling data out directly from Excel. No timestamps, no qualities, no browsing for tags, crappy syntax, worse than DCOM when connecting remotely.

OPC gives you timestamps, qualities, the ability to browse for tags, and is easier to configure for remote connection. Downside is that you'd need to code something up using the VB OPC Automation dll, and that can be a bit of a bear. Other option is to just use an OPC Excel plug-in that does all that work for you.

There's a more involved OPC vs DDE explanation on the OPC Exchange Blog.

 

[adrielmichaud]

Thinking about it a bit more, this question comes up a lot (DDE, OPC, VB for Excel access).

I cranked out a quick video showing how each of these options looks and feels like. It's not a be-all-end-all comparison of all the different ways, just a good overview.
http://www.youtube.com/watch?v=hHhQlQoVl3w
And yes, I know I say "umm" too much!


Covered:
-Accessing an OPC Server that supports DDE from Excel
-Pushing data into Excel using DDE
-Using a VB Automation dll to get OPC data into Excel
-Using an Excel OPC plug in

 

[Duranthas]

Thanks for the reply. I really like your OPC-2XL program but unfortunately I can't see my employer buying this, which is why most of anything I get I'll have to make myself. I'll keep looking for some vb code examples.

 

[Archie]

What PLC are you reading/writing data to?

 

[Duranthas]

PLC 5 and SLC5/04, all DH+. Well, actually it's ethernet to going into a contrologix chassis w/o a processor and a ENBT and DH/RIO card, then hopping onto the DH+ network.
The OPC server (if you can call it that I guess), is RSLinx Gateway. I've made ugly Excel macros that pull/push using DDE, and a very ugly program that pulled some data. I was thinking that if I make something from scratch for daily transfers I should go OPC, but after reading more on it I'm reconsidering.

 

[Archie]

If you could get to the RS232 port on the SLC 5/04, you can set the pass thru bit and use this driver that is free, it is much more efficient than DDE and OPC:

http://sourceforge.net/abdf1

http://www.youtube.com/watch?v=CiPzqc5jDlE

If you set the node property, you can access the various processors. I used it in that scenario talking to multiple SLC 5/04's, but I'm not sure if it will talk to the PLC5's.

 

[Duranthas]

I wish it were so easy.... the console computer is the only one connected to the DH+ network. I'm trying to remember but I think there is a RS232 port on my PLC5. I'll try to get a look at it tomorrow but that's going to be iffy since I'm being pulled into a couple of other projects.

 

[kdcui]

Sorry to resurrect a month old thread, but I am trying to write through Excel some code read and write data from a ControlLogix processor.

I know how to do it using DDE (ie RSLINK|'Topic'!'Item' format), but was thinking that a OPC interface would be much nicer. Not quite sure where to start.

Or for something this simple and I better off just suing DDE conversations?

 

[timucincelik82]

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