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Mobile hydraulic equipment controlled from a smartphone over BLE

No network, no screen: the operator's smartphone is the HMI via Bluetooth LE, with safety always in the PLC.

Runs on: ESP32 PLC 38R — Arduino sketches (.ino).

The application

A manufacturer of mobile hydraulic equipment needed the operator to control loading and unloading without installing a screen or a network on the machine. The ESP32 PLC 38R exposes a BLE UART service: the app sends motion commands and receives telemetry (pressure, temperature, flow, counters) every second. Cycle counters survive reboots in NVS memory, a hardware watchdog restarts the equipment if the firmware hangs, and overpressure protection lives in the PLC, never in the app.

Architecture

• BLE UART service (Nordic) — [M]x* commands and [T][P][F] telemetry
• EVC/EVD/EVG solenoid valves on relays with a state machine
• 4-20 mA sensors with unit conversion and broken-loop detection
• Persistent counters in NVS with deferred writes
• 20 s hardware watchdog + autonomous overpressure shutdown

Bill of materials

• ESP32 PLC 38R — Industrial Shields controller
• 3× hydraulic solenoid valve — loading / unloading / main
• 4-20 mA transducers (0-250 bar pressure, temperature) — telemetry
• Inductive sensor — pulse-based flow measurement

What is in the pack

• ble-mobile-app-control-38r.ino
• hardware-watchdog-38r.ino
• load-unload-solenoid-valves-38r.ino
• nvs-persistent-counters-38r.ino
• pressure-temperature-4-20ma-sensors-38r.ino
• pulse-flow-meter-38r.ino
• rtc-sync-over-ble-38r.ino
• Bill of materials + README