Can we connect to PLC over OPC (not using driver), either OPC-UA or DA. Is there any Siemens/Allen-Bradley PLC that supports this communication?
Also, in the setup where Ignition is connected to any PLC using drivers available in Ignition, which one is server, Ignition or PLC?
Anything implementing OPC would be considered a driver…
So your question is a bit strange.
However, there are PLCs that support OPC natively (from the manufacturer), like Siemens S1500 or AB (but I have no experience with AB). For Siemens, you do need to have an extra license.
When Ignition is connected to a PLC, the PLC is generally the server (it serves the info to Ignition). When you have Ignition to something else, Ignition can play the server too, and pass on OPC data to something else.
Siemens S7-1500 have a built in OPC UA server.
Thank you @Sanderd17 @Kevin.Herron for your reply.
I meant creating connection with PLC in OPC Connections (under OPC Client) instead of Device Connections (under OPC UA) in gateway page. In Device Connections, we need to select the specific driver.
While we are on this topic, can you please clarify my understanding about OPC?
What I understand is OPC is a universal protocol/language (may be like English). Whereas PLCs speak non-universal protocol/language (local language).Driver is means for translation which is used by OPC servers like Kepware, Ignition. So, when PLC like Siemens 1500 speaks OPC, no driver will be required for software that speaks OPC as well.
Is this understanding/analogy correct? Please guide.
In the past, most PLC brands have created their own language. That language was (and often still is) used for communication between devices, but is usually limited to a single brand.
If you wanted to communicate from one brand to another, you needed to have a translation service (like kepware), with all setup and maintenance issues that came with it.
OPC and its successor OPC-UA try to make that communication easier by creating a standard language. At the start, you still needed an external translation service between the brand’s language and OPC (f.e. Kepware). But at least this made it easier for 3rd party applications as they could just use opc to get it working.
Recently, more and more PLC brands saw the advantage of speaking a standard language, so they started adding opc as a secondary language to their own products (sometimes by default, for others you need to buy an additional license, and/or install an additional module).
When a plc offers opc communication, it usually needs to be considered as the opc server. So in ignition you can add it to the list of opc servers. There you only need to configure its endpoint (the address to communicate on), and optionally some login information. You don’t need to select the driver, as the driver is the opc-ua driver.
Your confusion is probably with the old OPC-DA protocol. That’s indeed available in ignition under the devices configuration, but isn’t used a lot anymore, and it’s honestly a pain to get working (so don’t use that one if you have the choice). Opc-ua is te newer, better default.
Thank a lot Sanderd17 for the clarification.