Write to opc ua nodes/machine attributes

Hi there,

I’m currently building an application to control a machine. The machine uses a Siemens PLC and I can connect to the PLC using OPC UA.

I have configured it as a machine with the opc ua data source and added some machine attributes. Now I can read these attributes in my application, but I can’t write to these attributes directly from the application.

Is there a way to write to the attributes and manipulate them in the opc ua node on my PLC?

I found a way using node-red, but it’s much more complicated to configure because I couldn’t find a direct way to write to node-red. So I had to set up a REST API connector between Tulip and Node Red to send data from Tulip to Node Red. To send data from Node Red to Tulip, I can use the machine attribute node.

Thank you in advance.

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Which OPC UA server do you use? (Embedded in PLC, Kepware, other, …)

I use the embedded OPC UA Server in the PLC. But I’m planning to integrate a Kepware OPC UA Server aswell.

If you plan to use Kepware, you can activate Kepware IoT gateway and expose « write tags » with REST protocol and after use HTTP connectors functions to send command to your PLC via OPC server. If Node-RED is embedded in your PLC you can as well expose an REST EndPoint. But with this architecture every PLC should have access to Tulip connector host (cloud or on-prem). The good choice depend on your scope and scalability priority

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So I have to use a HTTP connector to connect to my device. There is no direct way to write to opc ua nodes with Tulip?

From my knowledge of the platform, not at the moment

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Okay, thank you. Then I have to use node red.

Is there any update on this? It would be very useful for creating machine HMI’s. This is something that is very easy to do in Ignition.
I built out a whole proof of concept machine code with python, using a free python OPC library to run the server.
I experimented with node red, it worked but it seems to add a whole bunch of extra steps for the exact same functionality of OPC. And I don’t trust node red to be as robust in an industrial controls application as OPC.
Then I set up the a test HMI, machine type, added the machine, connected all the attributes. The whole thing.
I was very disappointed when to read this thread. Writing to OPC devices seemed like such an obvious feature.
Is the ability to write to OPC devices something that will be added in the near future?

Not the end of the world though. I can still use the OPC for monitoring and figure out a different way to send the control commands.

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Hey @seamuss1

I am the Product Manager who is responsible for the machine monitoring offering at Tulip. Write to OPC UA is something that is absolutely top of mind for the team. We are moving into doing our planning for 2024 as we speak. Current thinking is that we will probably tackle MQTT write, ahead of OPC UA write for a few reasons, but with this work, we plan to implement patterns in the product to make it quite straightforward to add OPC UA write.

We have been fairly sluggish implementing OPC UA write for concerns around giving customers features that can be used in ways that could incidentally damage machinery. We want to tackle this need, we are just also committed to doing it responsibly.