Industrial Embedded Data Logger (ESP32 + Modbus RTU)

Challenge

A manufacturing facility had temperature, humidity and pressure sensors with a Modbus RTU interface — an older protocol with no network connectivity. Data was read once a day by a technician with a laptop. The client wanted real-time monitoring and alerts when parameters go outside normal ranges.

Solution

ESP32 with RS485 module as Modbus RTU → MQTT gateway. FreeRTOS with two tasks: Modbus read every 10s and MQTT publish every 60s. When WiFi is unavailable, data is written to SD card with timestamps; when connectivity returns, automatic sync to the broker (Mosquitto on VPS).

Grafana + InfluxDB on VPS as visualisation and alerting layer. Alerts configured per parameter per zone (Hall A, Hall B, Cold Storage) with escalation: email → SMS after 30 minutes without acknowledgement.

Firmware updated via OTA (ESP32 Arduino OTA) — no need to physically access the device for updates.

Results

• 99.7% uptime over 12 months of production operation
• Zero data loss on WiFi outages (SD buffer + auto-sync)
• Client detected compressor failure 4 hours before physical breakdown based on temperature anomalies