Multi-Site PLC-to-Cloud Flow using HiveMQ Edge + Cloud

Connecting industrial PLCs securely from multiple sites to the cloud has never been this simple.

In this guide, we’ll see how HiveMQ Edge and HiveMQ Cloud can be used together to bridge data from Siemens and Allen-Bradley PLCs — using OPC UA, Modbus TCP, and MQTT.

System Overview

This setup demonstrates a multi-site architecture:

• Site A: Process running with Siemens S7-1500 PLC

• Site B: Process running with Allen-Bradley Micro850 PLC

• Both sites send local PLC data to HiveMQ Edge

  • Site A: Siemens S7-1500 PLC via OPC UA

  • Site B: Allen-Bradley Micro850 PLC via Modbus TCP

• A secure MQTT Bridge on HiveMQ Edge transfers data from the Edge devices to the HiveMQ Cloud

Step 1 – Connect PLCs to HiveMQ Edge and assign a local MQTT Topic

LIVE data in the S7-1500 PLC

LIVE data in the Micro850 PLC

a) Siemens S7-1500 (OPC UA)

Install HiveMQ in the edge device. In this case, we are using Revolution Pi as an edge device where HiveMQ Edge has been installed.

To learn more about how to install HiveMQ Edge on the edge device, check out this page.

Navigate to the HiveMQ Edge → Protocol Adapters, add a new OPC UA Protocol Adapter. Configure the connection details of your S7-1500 using the OPC UA endpoint, and select the OPC UA tag.

Then create a northbound mapping to publish it as:

Topic: machine/s71500/rTemp

This allows HiveMQ Edge to read OPC UA values and push them to the local MQTT broker.

b) Allen-Bradley Micro850 (Modbus TCP/IP)

Similarly, install HiveMQ in another edge device. In this case, we are using a reComputer from Seeed Studio as an edge device where HiveMQ Edge has been installed.

To learn more about how to install HiveMQ Edge on the edge device, check out this page.

Add a Modbus Protocol Adapter and connect to the Micro850 PLC via MODBUS TCP/IP.

Select the tag Current_Temp and map it to the following topic:

Topic: machine/micro850/rTemp

Each tag update will now be converted to MQTT messages locally.

Step 2 – Creating the MQTT Bridge

In both HiveMQ Edge → MQTT Bridges, create a bridge to your HiveMQ Cloud Cluster. Once connected, data from both sites is securely forwarded to the cloud broker.

MQTT bridge in Revolution Pi

MQTT bridge in reComputer

Step 4 – Visualizing Data on HiveMQ Cloud

Log in to your HiveMQ Cloud Web Client, subscribe to your topic (e.g., #), and you’ll start receiving live messages as shown below:

You can now view, analyze, and integrate these values into dashboards or data platforms.

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🧠 Step 5 – Understanding the Data Flow

From each PLC:

• Data is read using OPC UA or Modbus TCP

• HiveMQ Edge maps the tags to MQTT topics

• The MQTT Bridge sends this data securely to HiveMQ Cloud

✅ Supports multiple sites ✅ Secure TLS connection ✅ Cloud-ready and scalable

🧩 Why HiveMQ Cloud?

• 🔒 Secure MQTT Bridge

• 🌐 Multi-site scalability

• ☁️ Cloud-ready architecture

• 💡 Perfect bridge between OT and IT

♥️ Work With Me

I regularly test industrial automation and IIoT devices. If you’d like me to review your product or showcase it in my courses and YouTube channel:

📧 Email: [email protected] or drop me a message on LinkedIn