Now that Node-RED is installed and the PLC is exposing OPC UA tags, it's time to establish a live connection and start reading values. This post will walk you through how to connect Node-RED to the virtual PLC running in PLCSIM Advanced using the OPC UA Client nodes.

Add the OPC UA Client Node to Flow

• Open Node-RED in your browser at http://localhost:1880

• Drag an opcua-client node from the sidebar into your flow

• Double-click it to open the configuration panel

Add OPC UA Read Nodes

Drag in an opcua-item node and connect it to the opcua-client node.

Each opcua-item represents one tag to read. Set the following:

Node ID: use the OPC UA Node ID format, typically:
ns=3;s="DB1.TagName"

•  For symbolic tags, you can find them in TIA Portal → PLC Tags → Symbol Table.

• Datatype: match the data type (e.g. Boolean, Int, Real

ns=3;s="GlobalDB.WorkpieceCounter"

Tip: Use UA Expert to browse and copy the exact tag names.

Add a Trigger (Inject Node)

To read values on demand or at intervals, connect an inject node to your OPC UA item node.

You can configure it to:

• Trigger every X seconds (for continuous updates, 0,5s for this project)

• Or manually trigger on button click (for testing)

View Results

Connect the OPC UA client node output to a debug node.

You can deploy your flow and refer to the debug tab (top-right sidebar) to ensure that values are being read correctly.

You should see the current state of your tag(s), like:

{"value":true,"datatype":"Boolean"}

Summary

• Node-RED is successfully connected to your virtual PLC.

• You can browse and read tag values in real time.

• You’ve set up a flow that polls PLC data and shows results in the debug panel.

This connection forms the backbone of your dashboard and monitoring logic.