I have tried to find a good way to use OPC tags in my VB programs but I cant! Can someone tell me how? I have found something about ActiveX objects but then you have pay for it. OPC is supposed to be an open standard!!!
> I have tried to find a good way to use OPC tags in my VB programs but I cant! Can someone tell me how? I have found something about ActiveX objects but then you have pay for it. OPC is supposed to be an open standard!!!
OPC is very new to me also. I hope the following helps:
The way I understand it, you can get the OPC standard and make your own client. But, it is easier to buy.
I have just completed my first trial VB 6.0 project communicating with an OPC Server. It works very well. I used an OPC Client demo from Rensen Information Services. You can download the demo at http://www.ris.co.nz/. For VB you use the risopcio.dll file. Information on how to use it is in the help. Other sources can be found at http://dspace.dial.pipex.com/opc/ click on free OPC clients.
Most of these are just demos. Eldridge Engineering seemed promising, but I haven't tried it yet. Licenses seem to be about U.S.$500 - $700.
As a vendor with an OPC Server, we get the "OPC Client" question very frequently. We have developed a bit of sample code in VB that shows how to create and use an OPC client using Visual Basic.
The sample code is available for download at our web site:
Thanks for the link. Your example works like a champ. For the OPC Clients, I guess it truly is free.
I was interested in you VB sample code for OPC clients, however, could not get through the security on your site. Could you let me know how I can get to your sample code? Regards, Peter Veselovsky firstname.lastname@example.org
Hi, we are a group of students in Norway and we are trying to make an OPC-client that works over ethernet. We downloaded your example and it
works fine when the OPC-server is on the same PC as the client. We canīt get it to connect to a server which is on the same network. Thatīs
why we opened a new VB project using the opcdaauto.dll and its methods but it still canīt find nor connect to another OPC-server. Have you
heard of any problems like this before? Are there any restrictions on the dll?
Grateful in advance
hiz. I am a student, currently doing a project on communiation between an OPC server with VB etc.
I have done it successfuly with the OPCActiveX but however I hope to do it without it.
I tried to search for the sample code you mentioned but was unsuccessful. Can you please email me a sample if it is convenient or leave a link for me. Tks a lot!
My email address is "email@example.com", mailto:firstname.lastname@example.org .
Why do so may people think that OLE is some 'open' source thing? OPC means "OLE (Object Linking and Embedding) for Process Control". It is no more a standard or open other than Microsoft Excel or Word, which are other examples of software that supports OLE. The difference is that OPC relates to software geared towards the controls industry.
I have personally developed software in VB using OPC to access tags from a DCS. The program allows users to plug in tags they wish to view, and the interface client trends these tags, by accessing the DCS via the OPC server.
A seperate acquisition program is used to generate historical data, which is then stored in a SQL backend.
There are white papers on the OPC site explaining how to access the OPC server via OPC commands from VB.
But, if you would like, you can email me directly and ill email you some of the code.... no problem.
> Why do so may people think that OLE is some 'open' source thing?
How can students then ever develop good programs? if we have to pay for every little bit we want to use: pay for computer, pay for bootloader, pay for OS, pay for Word processor, pay for development toolkit, pay for hardware, pay for internet. Do we have to pay to get the hardware drivers to get it working properly with all the rubbish we just bought too? It's like making cars that can't be opened by anyone than by the garage, no one is allowed to see what's inside them. Or like making televisions without screws and use other protection methods to hide the components. (thank god the library is free, else the world would have never come this
The joys of being a student, the first lesson well learned, everything costs money, now for the next lesson, how to make some of your own!!!!!!!!!
If you're a home builder, you buy your hammers and saws, etc...
If you're an electrician, you buy your screwdrivers, volt meters, etc...
If you're an artist, you buy paint, brushes, and canvas...
Doctors buy stethoscopes (and other far more expensive equipment)...
Ditch diggers buy shovels...
But Computer Programmers are supposed to get everything free?
... But 5 years later I can still use my hammer (or voltmeter or paintbrush or stethoscope...)!
Creating a future should not be done on the back of charity. You learn it
and earn it. It is only when you pay for the knowledge and experience in
software that you understand you own worth when you do it.
How would you feel if you were expected to create software for your client and not get paid.
Note: Educational discounts are almost always available from vendors. or crippled programs so that you cant make a lot of money using the product. I would investigate that.
PS Welcome to the real world:) and good luck
Jeremy Pollard, CET
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> Creating a future should not be done on the back of charity.
That depends on what kind of future you're trying to create :-)
> You learn it and earn it. It is only when you pay for the knowledge and
> experience in software that you understand you own worth when you do it.
True; on the other hand, until recently, software was one of the few cases where you weren't allowed to take it apart to see how it worked. (This is also now illegal for computers themselves, dvd players, etc. Even in your car there's a screw on your carburettor you aren't allowed to touch.)
> How would you feel if you were expected to create software for your
> client and not get paid.
Most software is custom rather than shrink-wrap, anyway. For custom s/w, you get paid for the customization work rather than software per se.
Entrusting your future to a partnership with a monopolist isn't very wise, by most accounts. The road to their success is paved with the
bodies of their former partners. And in the end, who ends up with all the riches? A little detachment brings a lot of perspective.
OK...You could simply reveal a simple sample to the other people see and learn...But if you dont, well, people will find a way...your standard may be bypassed (or simple become obsolete) by some kid with a good idea and all of you "experienced programmers" will ask why are you loosing your jobs...but, youll find a way too....
think about it, to share is multiply !