Integrating SCADA Systems with IoT Protocols Using Node-Based Edge Gateways

The Challenge of Legacy Industrial Data

In factories and power plants around the world, process control has historically relied on systems known as SCADA, which stands for Supervisory Control and Data Acquisition. In practice, this means computer screens in control rooms display tank temperatures, motor speeds, and valve flows in real time, allowing operators to make quick decisions. However, these systems were designed decades ago when the absolute priority was isolated and secure functioning within a closed network, without any connection to the external internet.

With the advancement of Industry Four Point Zero—the fourth industrial revolution focused on complete digitization—the urgent need arose to send this operational data to the cloud. The goal is to apply artificial intelligence, create management dashboards accessible from anywhere, and predict equipment failures before they break. The major problem is that most programmable logic controllers, known as PLCs, communicate only through old and rigid dialects like Modbus, which were never built to travel efficiently across the modern internet.

Understanding the Technological Bridge with Node-RED

To bridge this communication gap without replacing all factory machinery, which would cost millions of dollars, engineers use a concept called edge computing. In practice, this involves placing a small, inexpensive computer, such as a Raspberry Pi or a dedicated industrial gateway, physically close to the machines. Node-RED runs on this intermediate hardware, offering a browser-based development tool that connects hardware devices, APIs, and online services through visual blocks dragged across a screen.

Node-RED acts as an extremely agile simultaneous translator. It features native and community nodes that speak traditional industrial protocols perfectly, collecting variables from PLCs and converting those data packets into the MQTT protocol, which is the global standard for the Internet of Things. MQTT operates like a lightweight and efficient postal system, ideal for sending small sensor messages across unstable or low-bandwidth internet connections, saving computing resources and ensuring information delivery.

Practical Architecture of an Industrial Gateway

Building an efficient edge gateway requires a well-planned network architecture that respects international industrial cybersecurity standards. Physically, the gateway features two distinct network cards or interfaces: one Ethernet port dedicated exclusively to the field network, where PLCs and sensors reside in an isolated subnet, and another interface with access to corporate internet or cellular networks to transmit consolidated data to the cloud.

This physical and logical separation prevents cyberattacks originating from the internet from reaching the critical core of the production line. In practice, Node-RED runs on this isolated gateway, acting as the local collector. It reads PLC Modbus registers every few seconds, temporarily stores the values in internal memory in case the internet drops, and as soon as connectivity is restored, transmits the accumulated data batches without losing history to the cloud dashboard.

Implementing Data Collection and Conversion

To get hands-on, the workflow inside Node-RED begins with a timed injection block that triggers periodic requests. Next, a Modbus read block sends a TCP or serial command to fetch the state of a switch or the analog reading of a temperature sensor. The code example below demonstrates the typical JSON structure that Node-RED builds after processing and translating raw PLC readings before publishing them via MQTT.

{
  "device_id": "assembly_line_02",
  "timestamp": 1718025600,
  "metrics": {
    "reactor_temperature": 85.4,
    "line_pressure": 4.2,
    "operational_status": true
  }
}

This standardized message format enormously simplifies the work of software development and data science teams in the cloud. Instead of dealing with complex hexadecimal memory addresses specific to each PLC manufacturer, they receive a clean, readable JSON object. This decouples the factory floor from software engineering, allowing new analytical dashboards to be built without impacting the stability of physical control systems.

Operational Challenges and Mitigation Strategies

Despite its ease of use, deploying Node-RED gateways in a factory environment requires rigorous engineering precautions. The first challenge is hardware reliability: memory cards in low-cost computers can corrupt after years of continuous log writing. Mitigating this issue involves setting the operating system to read-only mode and directing all temporary logs to RAM, reducing physical storage wear.

Another critical point is network failure management. Since industrial networks frequently experience instabilities, the Node-RED flow must include local queue storage blocks, known as store-and-forward. When the internet fails, data is saved in a lightweight embedded database, such as SQLite. As soon as the signal returns, records are dispatched in chronological order, ensuring no safety events or temperature spikes go unnoticed by on-call engineers. To complement this implementation in production environments, see our related technical analyses on Integrating SCADA Systems with Low-Power IoT Protocols Based on MQTT-SN over Mesh Networks and Industrial IoT Device Integration via Edge Gateways with MQTT and OPC UA Protocol Normalization.

Final Considerations

Integrating traditional SCADA systems with the flexibility of IoT protocols using Node-RED gateways represents the most pragmatic path for industrial modernization. This approach eliminates technological obsolescence without requiring exorbitant investments to replace decades-old control panels. By decentralizing processing to the network edge, companies gain agility, reduce cloud data traffic costs, and build a solid foundation for complete digital transformation.