Milesight UR75 and Node-RED: Industrial Automation Without the PLC Leave a comment

The hidden cost of traditional industrial automation

A PLC that reads energy meters, sends alarms, and forwards data to a SCADA platform sounds straightforward. In practice, it means a PLC licence, an engineer to write the ladder logic, a site visit every time requirements change, and separate hardware for your cellular connection. For a remote substation or a pump station in a field, that adds up fast. The hardware cost is often the smallest part.

The Milesight UR75 takes a different approach. It is a 5G industrial router that also runs Node-RED natively on the device. That means your edge logic, your protocol conversion, and your cellular backhaul all run on one DIN rail device, without an external computer, without a PLC, and without a site visit to change the logic.

What is a Node-RED router?

Node-RED is an open-source visual programming platform developed by IBM and now maintained by the OpenJS Foundation. Engineers build automation flows by connecting blocks on a canvas rather than writing code line by line. Each block handles one task: read a Modbus register, parse a value, publish to MQTT, send an HTTP request, trigger an alert. Connect the blocks, deploy the flow, and it runs.

On most installations, Node-RED runs on a Raspberry Pi, an industrial PC, or a cloud server. The problem is that each of those needs its own power supply, enclosure, network connection, and maintenance window. Running Node-RED on the UR75 eliminates the extra hardware entirely. The router handles the cellular connection, the serial port wiring, the digital I/O, and the edge logic in the same enclosure, from the same power rail, on a platform rated to -40 to +70 °C.

What the Milesight UR75 brings to this

• 5G Sub-6 GHz backhaul: NSA and SA mode, up to 4.67 Gbps downlink via dual carrier aggregation, with automatic fallback to 4G LTE and WCDMA.
• Dual SIM failover: two Mini SIM slots with automated failover and failback across networks.
• RS232 and RS485 serial ports: direct connection to PLCs, RTUs, meters, and SCADA field devices. Modbus RTU to Modbus TCP gateway function built in.
• Digital I/O: one DI and one DO, both galvanically isolated, for discrete sensor inputs and relay outputs.
• Node-RED built in: runs on the device. No additional hardware. Flows deploy via the web UI.
• Quad-core ARM Cortex-A55, 1 GB RAM, 1 GB flash: enough headroom for complex flows alongside normal routing functions.
• M.2 NVMe SSD slot: expandable local storage for data buffering and logging.
• GNSS: GPS, GLONASS, BeiDou, Galileo, and QZSS for timestamping and position data.
• Wi-Fi 6 dual-band: 2.4 GHz and 5 GHz concurrent with MU-MIMO.
• 5 x Gigabit Ethernet: 1 WAN and 4 LAN. PoE PSE on all four LAN ports on the UR75-504AE-P-W2 variant (802.3af/at, 30 W per port, 60 W total).
• -40 to +70 °C, IP30 metal housing, DIN rail mountable: genuine industrial specification.

What can you build with a UR75 and Node-RED?

Modbus RTU to MQTT without a PLC

This is the most common deployment pattern. You have an energy meter, a pump controller, or an inverter with an RS485 Modbus RTU interface. You want the readings in a cloud dashboard, an Azure IoT Hub, or an AWS IoT Core endpoint. Traditionally that means a Modbus RTU/TCP converter, a separate cellular router, and either a gateway PC or a cloud-side translator.

On the UR75, the flow is simpler. The RS485 port connects directly to the field device. A Node-RED flow polls the Modbus registers at whatever interval you set, maps the values to a JSON payload, and publishes to MQTT. The 5G link carries the data to your broker. No additional hardware. The built-in Modbus gateway also allows direct SCADA polling over TCP if you need both paths simultaneously.

This pattern is directly applicable to smart metering, BESS monitoring, solar inverter telemetry, and remote substation RTU polling.

Remote tank and level monitoring

A level sensor on an RS485 bus sends readings to the UR75. A Node-RED flow compares each reading against a threshold. When the level drops below the alarm point, the flow triggers an MQTT message to your monitoring platform and an SMS alert via the built-in SMS management function. No cloud round-trip is needed for the alarm decision. The edge logic runs on the device, so the alert fires even during a brief connectivity window.

The DI port handles a float switch or a dry contact alarm input from a pump. The DO port can trigger a relay. This combination covers most water and wastewater telemetry requirements without a separate PLC or RTU.

CCTV health monitoring for installers

Node-RED can run periodic HTTP checks against each camera IP on the LAN. If a camera stops responding, the flow logs the event, publishes to MQTT, and sends an alert. The DO port can trigger a relay to cycle power to a PoE switch port if you are using the UR75-504AE-P-W2 variant with PoE PSE output.

Combined with a fixed IP SIM card, remote access to the Node-RED editor and the camera streams is straightforward without additional VPN hardware. MilesightVPN handles the encrypted tunnel back to your monitoring station.

EV charge point monitoring and management

OCPP-compliant EV charge points communicate over TCP. Node-RED flows on the UR75 can parse OCPP messages, extract session data, and forward status updates to a fleet management platform or an Azure IoT Hub endpoint. The 5G backhaul handles the throughput, and the dual SIM failover maintains connectivity at sites without a wired connection.

For larger sites, the PoE variant powers multiple charge point controllers directly from the LAN ports. The GNSS module provides precise timestamping for billing and audit records without a separate NTP server.

Building management system integration

Building management systems typically use BACnet or Modbus over IP. Node-RED on the UR75 acts as middleware: it polls BACnet objects or Modbus registers from HVAC controllers, lighting systems, and energy meters, normalises the data, and forwards it to a central platform via MQTT or HTTP. Where the UR75 replaces a wired connection that has failed or is cost-prohibitive, the 5G link provides the backhaul. Changes to the integration logic deploy from the web UI without a site visit.

Smart grid and substation telemetry

Substations running IEC 61850 or DNP3 over serial produce large volumes of event and measurement data. RS485 on the UR75 handles the serial side. Node-RED flows parse the protocol messages, map them to a standardised schema, and forward to a SCADA head-end via MQTT or a direct TCP connection. The GNSS module provides IEEE 1588 PTP-compatible timestamps for sequence of events logging. Dual SIM across different MNOs provides the redundancy that NIS/CSRB frameworks require for critical national infrastructure assets.

Node-RED versus a PLC: a practical comparison

The question engineers ask most often is whether Node-RED on a router is a credible alternative to a PLC for remote site automation. For the majority of telemetry, data forwarding, and alert-triggering use cases, the answer is yes.

• PLC licence cost: entry-level PLCs with Ethernet and serial interfaces typically start at several hundred pounds, before software licences and engineering time. The UR75 includes the Node-RED runtime at no additional cost.
• Logic changes: modifying a PLC program often requires proprietary software, a trained engineer, and sometimes a site visit. Node-RED flows edit in a browser and deploy over the network in seconds.
• Cloud and MQTT integration: native in Node-RED. Adding Azure IoT Hub or AWS IoT Core output to a PLC typically requires additional middleware or a specialist integration module.
• Cellular backhaul: a PLC requires a separate cellular router. On the UR75, the router and the edge computer are the same device.
• Hardware count: one device replaces the cellular router, the protocol converter, and the edge computer. Three items become one.

Node-RED on a router is not a replacement for safety-critical PLC functions, high-speed motion control, or complex machine logic. For remote monitoring, telemetry forwarding, protocol conversion, and conditional alerting, it handles the task with significantly less hardware and lower ongoing cost.

Why edge computing matters for industrial IoT

When every sensor reading travels to the cloud before a decision is made, you are dependent on the cellular link for every event response. A brief dropout delays the alert. A sustained outage stops automation entirely.

Running logic on the UR75 means the decision happens locally. The MQTT publication to the cloud is informational; the action has already taken place. For alarm triggering, relay control, and data buffering, edge processing produces faster and more reliable outcomes than cloud-first architectures. The M.2 NVMe SSD slot provides local storage for data buffering during connectivity gaps, with automatic catchup when the link restores.

Frequently asked questions

Does the Milesight UR75 come with Node-RED pre-installed?

Yes. Node-RED is included in the UR75 firmware as a built-in application. It is accessible from the router web UI under the Applications menu. No additional installation is required. You access the Node-RED editor via a browser pointed at the router’s LAN IP.

What Modbus functions does the UR75 support?

The UR75 supports Modbus RTU over RS232 and RS485, and Modbus TCP over Ethernet and cellular. The built-in Modbus gateway function translates between RTU and TCP, so SCADA platforms polling over TCP can reach serial field devices directly. Node-RED adds Modbus read/write nodes for custom polling intervals, register mapping, and conditional logic on top of that.

What SIM card do I need for a remote UR75 deployment?

For most remote monitoring and VPN deployments, a fixed IP SIM card is the correct choice. Standard SIM cards sit behind carrier-grade NAT, which blocks inbound connections and complicates VPN setup. A fixed IP SIM gives the router a reachable address for remote access, SCADA polling, and MilesightVPN tunnels. We supply IoT and M2M SIM cards alongside the router if needed.

Can I access the Node-RED editor remotely?

Yes, via MilesightVPN or any VPN tunnel configured on the router. MilesightVPN provides an encrypted tunnel back to your management station without requiring a fixed IP on the office side. With a fixed IP SIM in the router, you can also reach the web UI and Node-RED editor directly over the cellular link from a remote client connected via IPsec or WireGuard.

What is the difference between the UR75-504AE-W2 and the UR75-504AE-P-W2?

Both variants are identical in cellular specification, processor, memory, Wi-Fi 6, GNSS, serial ports, DI/DO, and Node-RED support. The UR75-504AE-P-W2 adds 802.3af/at PoE PSE output on all four LAN ports at 30 W per port with a 60 W total budget. This is the right choice where downstream devices such as IP cameras, LoRaWAN gateways, or access points need to be powered over Ethernet from the same device.

Is Node-RED on a router suitable for safety-critical applications?

Node-RED on the UR75 is appropriate for monitoring, alerting, data forwarding, protocol conversion, and non-safety-critical control tasks. It is not certified for SIL-rated safety functions or applications where a failure could cause physical harm. For those applications, a certified PLC or safety relay remains the correct choice. The UR75 and Node-RED can run alongside safety-rated hardware, handling the telemetry and communication layer while the PLC manages the safety-critical logic.

Related products and further reading

The Milesight UR75-504AE-W2 is the standard variant without PoE. The Milesight UR75-504AE-P-W2 adds 802.3af/at PoE PSE on all four LAN ports. For deployments requiring a fixed IP address for inbound SCADA polling or remote access, see our fixed IP SIM cards. For 4G IoT and M2M applications where 5G coverage is not yet available, our IoT SIM cards provide multi-network roaming and data management. Browse the full Milesight router range for the complete Ultra Series line-up.