IoT Diesel Generator Fuel Theft Alert System with Level Sensing and Runtime Logging (ESP32)

Diesel generator sets in hostels, hospitals, housing societies and small industrial units sit unattended for long stretches, and the fuel inside their tanks is easy to siphon off without leaving obvious traces. The loss usually surfaces only when a dip-stick check is done or when the generator runs dry during an outage, by which time there is no record of when the level actually fell. Owners also rarely know how many hours a set has run between refills, so consumption cannot be reconciled against runtime. This project builds a monitoring node that watches the tank continuously: an ultrasonic sensor measures the diesel level from above, the controller separates genuine consumption during running hours from unexplained drops while the set is off, and a GSM link reports theft and low-fuel events by SMS while every event is logged against time.

1. The HC-SR04, fixed in a bracket above the test tank, fires an ultrasonic pulse at intervals; the ESP32 times the echo from the diesel surface and converts the air-gap distance into fuel level using the calibrated empty and full heights.
2. A burst of repeated readings is median-filtered to reject sloshing and surface ripple, and the filtered level is converted to approximate litres from the tank's cross-section before being stored with a timestamp.
3. A non-invasive sense circuit on the DG output reports RUNNING or OFF to a digital input; while the set runs, level changes are booked as consumption and added to the runtime log with start and stop times.
4. While the set is OFF, the firmware compares each new filtered level with the last stable stored level; a drop beyond the configured theft threshold within the check interval raises a theft event.
5. On a theft event or a low-fuel crossing, the ESP32 commands the SIM800L over its serial interface to send an SMS naming the event, the level before and after, and the time, to the configured number.
6. Level samples, runtime records and alert events are served to the dashboard, which draws the level history chart, updates the gauge and lists the newest events first.
7. The node keeps sensing on its regulated supply, and the event log is retained in non-volatile storage so a power interruption does not erase the theft and runtime history.

Tech stack:

• ESP32 (Wi-Fi + Bluetooth SoC, used as controller)
• HC-SR04 ultrasonic ranging module
• SIM800L GSM/GPRS module · SMS alerts
• Non-invasive DG output sense circuit
• Arduino IDE (C/C++ firmware)
• HTML · CSS · JavaScript dashboard
• Median filtering · level calibration in firmware
• Regulated 5 V / 4 V-class DC supplies

• [Non-contact ultrasonic level sensing] An HC-SR04 sensor mounted above the diesel surface measures the air gap to the fuel, and the ESP32 converts that distance into level and approximate litres using the test tank's calibrated height, so nothing is dipped into the fuel itself.
• [Theft detection while the DG is off] The firmware compares the stored level with the current level at intervals; a drop larger than the configured threshold while the generator output sense reads OFF is treated as a theft event rather than normal use.
• [Runtime sensing on the DG output] A non-invasive sense circuit on the generator output tells the controller whether the set is running, so fuel consumed during genuine running hours is logged as consumption and never flagged as theft.
• [SMS alerts over GSM] A SIM800L module sends theft-alert and low-fuel SMS messages to a configured mobile number, so an alert reaches the owner even where there is no Wi-Fi coverage at the generator site.
• [Runtime hours logging] Start and stop times from the output sense are accumulated into total runtime hours and per-day run records, letting fuel filled, fuel consumed and hours run be compared side by side.
• [Low-fuel refill alert] When the measured level crosses the configured low-fuel mark, the system raises a refill reminder by SMS and marks the event on the dashboard before the tank reaches the pickup limit.
• [Local dashboard with level history] A web dashboard shows the current level gauge, a level-versus-time history chart, the runtime log and the alert event list, so the complete behaviour of the node can be demonstrated from one screen.
• [Configurable thresholds] Theft drop, low-fuel level and sensing intervals are firmware parameters (configurable in code) — they can be retuned for a different tank height or alert preference; a larger industrial tank fitment is an optional customisation, not part of the base build.

• Working fuel-theft monitoring prototype (ESP32 node, HC-SR04 on tank bracket, SIM800L with antenna, DG output sense circuit, test tank assembly)
• Controller firmware / source code with level sensing, theft logic, runtime logging and SMS alert code
• Dashboard demo (single-file web app) showing level gauge, history chart, runtime log and alert events
• Circuit diagram, wiring documentation and component list
• Tank calibration and threshold setup instructions
• Project report PDF (background, sensor theory, theft-logic design, methodology)
• Project abstract PDF
• PPT presentation for final review
• Viva Q&A preparation document (ultrasonic ranging, GSM AT commands, filtering, runtime reconciliation)