ThingsLog 4G MQTT Modbus Controller

Modbus Protocol — Industrial IoT Standard

Modbus is the most widely used communication protocol in industrial automation — implemented by virtually every PLC, VFD, smart meter, and sensor transmitter manufactured in the last 30 years. ThingsLog’s 4G MQTT Modbus Controller speaks Modbus RTU (RS-485) and Modbus TCP natively, enabling it to connect to any industrial device without gateways or protocol converters. This makes it the bridge between the OT (Operational Technology) world of industrial field devices and the IT world of cloud platforms and analytics — connecting legacy industrial infrastructure to modern IoT platforms without replacing existing equipment.

MQTT — The IoT Messaging Protocol

MQTT (Message Queuing Telemetry Transport) is the de facto standard for IoT data transmission. It is lightweight and efficient, designed for unreliable networks and constrained devices — ideal for 4G connections in remote industrial locations where signal quality may vary. ThingsLog uses MQTT over TLS for encrypted, authenticated communication between the controller and the cloud platform or any third-party MQTT broker. MQTT’s publish-subscribe architecture enables near real-time data delivery and remote command sending with sub-second latency once the connection is established, supporting both monitoring and control use cases over the same communication channel.

SCADA Integration with ThingsLog Modbus Controller

Connecting Field Devices to SCADA

The controller reads data from PLCs, VFDs, pressure transmitters, flow meters, and level sensors via Modbus RTU over RS-485, and publishes it via MQTT to the ThingsLog cloud or directly to an on-premises SCADA server. This creates a seamless data path from field instruments to the control room without custom protocol translators, middleware servers, or proprietary communication hardware. Engineering teams familiar with Modbus register mapping can configure the controller directly from the ThingsLog platform without specialist IoT expertise.

Remote Control Commands

The SCADA system or ThingsLog platform sends control commands — pump start and stop, valve open and close, setpoint change, mode selection — via MQTT to the controller, which executes them as Modbus write commands to the target field device. Command acknowledgment and execution status are returned to the platform within seconds, confirming successful execution. This bidirectional communication makes the ThingsLog controller a true remote terminal unit (RTU) for SCADA applications, not merely a data acquisition device.

Alarm and Automation Logic

The 4G MQTT Modbus Controller supports on-device automation logic that executes locally without requiring a cloud round-trip. Threshold-based alarms — tank overflow, low pressure, high temperature, pump fault — trigger relay outputs immediately when the monitored value crosses the configured threshold, even if the cellular connection is temporarily lost. Timed switching sequences control pumps, lights, or valves according to configurable schedules. Fail-safe logic executes predefined actions if cloud communication is lost for more than a configurable timeout period, ensuring critical processes continue in a safe state during network outages.

Controller Deployment Examples

Pumping Station Automation

Read pump status, flow rate, pressure, and power consumption from Modbus instruments connected to the pump set. Control pump start and stop commands and VFD speed setpoint for variable flow applications. Alert operators on pump failure, abnormal vibration, or pressure outside normal operating range. Energy monitoring and pump efficiency reporting enable predictive maintenance scheduling based on actual operating data rather than fixed time intervals.

Street Light Control Cabinet

Monitor electricity consumption per lighting circuit, control lighting segments individually or by group, and detect cabinet door tampering or unauthorised access. Implement astronomical time schedules with automatic seasonal adjustment — lights switch on at actual sunset and off at actual sunrise for any geographic location — eliminating the need for manual schedule updates throughout the year.

Agricultural Irrigation Control

Control multiple irrigation valve zones sequentially or simultaneously based on time schedules or soil moisture sensor triggers. Monitor flow rate and cumulative volume per zone, tank levels, and pump pressure. Implement moisture-based irrigation scheduling: irrigate when soil moisture drops below the agronomic threshold and stop when the target moisture level is reached — automatically adjusting for actual crop demand rather than fixed calendar schedules.