Using OPC with Siemens TI 505 PLC for LabView

[m_a_b]

I'm a ChemE student working on automating a polymer extrusion line using a Siemens TI 555 plc. We are using LabView and I have been searching for a driver for our plc for a while with no luck, so I think I will have to use the OPC server, which, according to this site, has a driver on the CD for the siemens 500 series plc's.

My question is, how does the OPC server work? Is it simply software that I install onto the pc or is it a separate piece of hardware? Is there anything I should know about, or be careful of, before I continue?

At the moment, I am really pretty confused about how all this comes together, so any help or points in the right directions are appreciated!

[Ben]

Hi m_a_b,

First I suggest you re-post this Q to the LabVIEW DSC discussion forum. LV DSC (Data-Logging and Supervisory Control).

Your OPC server will generally be a seperate software app that will run on your PC that you will have to configure to do what you need. The specifics of configuring I will not go into now. You will have configure the OPC server to let it know how to get at the PLC and what registers (coils?) you want to access, how often, and if read, write or both access is required.

Now on the topic of "get at the PLC"
I can't recite details so check me on the following.
Your PLC will dictate the commnications medium and protocol you will use. I would guess ethernet or S7. Ehternet is straight forward. S7 is supprted by NI when last I checked.

Once your OPC server is up and running, you can then use DataSockets to read from or write to whatever you configured in the OPC server, and use it in your LV app.

If you plan to devlop an app that will scale well to more than 100 I/O points (i.e. datasockets) then I suggest you include LV-DSC in your application developement plans.

LV-DSC will let you configure "Tags" which are just I/O points. They can be control registers in PLC's, DAQ or DIO.... in the LC-DSC tag Engine. Configuring just amounts to navigating till you find the I/O point yu are after. The Tag Engine does all of the work of monitoring the tag and doing all of the dirty work in you behalf. And it does it well!

If you skip DSC and try to scale a datasocket based app, your CPU and network demands will scale linearly with the number of datasockets because each data socket operation is distict from each other and handled seperately. If DSC is used, the I/O's are batched and performance is optimized.

As I mentioned up front, re-post to the DSC group, that where the PLC frequent flyers are.

I hope this gets you started.

Ben


Ben Rayner
Certified LabVIEW Developer
www.DSAutomation.com