IoT LPG Gas Leakage Detector with Auto Shutoff Valve

LPG leaks are dangerous precisely because the gas is invisible and the failure mode is binary: either someone smells it in time or they don't. Standalone gas alarms only beep — if nobody is home, the beep protects nothing, and none of them can stop the leak. The engineering gap is a node that both senses and acts: detect the leak, cut the supply automatically, and notify someone who can respond, with the whole event visible remotely. This project builds that node on an ESP32: an MQ-6 semiconductor gas sensor (sensitive to LPG in the 200–10000 ppm band per its datasheet) feeds the controller; on crossing the alarm threshold the firmware sounds a buzzer, drives a normally-closed solenoid valve shut on the gas line, and publishes the event plus live PPM readings to a cloud dashboard. The dashboard renders a live concentration gauge, valve status and a timestamped event log, and sends the alert to the user's phone. A manual reset and valve self-test routine complete the safety logic.

1. The MQ-6 sensor heats its sensing element; after the documented warm-up/burn-in period the ESP32 samples the divider voltage.
2. The firmware converts the reading to an approximate LPG concentration using the sensor's characteristic curve (documented as indicative, not laboratory-grade).
3. Crossing the pre-alarm threshold starts intermittent buzzing and a dashboard warning; crossing the alarm threshold escalates.
4. On full alarm the ESP32 de-energizes the normally-closed solenoid valve (spring shut), sounds the continuous buzzer, and publishes the event with PPM and timestamp.
5. The dashboard raises the alert on the user's phone; the event log records the full sequence for the report.
6. Once readings fall below the safe band, a manual reset re-energizes the valve; the self-test routine verifies valve movement on schedule.

Tech stack:

• ESP32 development board (Wi-Fi)
• MQ-6 LPG gas sensor module
• Normally-closed solenoid valve (gas-line rated) with driver relay/MOSFET
• Buzzer and status LEDs
• 12 V power supply for valve + 5 V logic supply
• Cloud dashboard (Blynk/ThingSpeak class) with live gauge and event log
• Arduino IDE (C/C++ firmware)
• Demo gas-test chamber accessories for calibration

• [MQ-6 LPG sensing] Semiconductor sensor with datasheet sensitivity to LPG in the 200–10000 ppm band; the load-resistor divider and burn-in procedure are documented.
• [Automatic shutoff valve] A normally-closed solenoid valve on the gas line is held open during normal operation and released shut on alarm — fail-safe by design, since power loss also closes it.
• [Two-stage alerting] A pre-alarm warning stage (buzzer intermittent) escalates to full alarm (continuous buzzer + valve shut + dashboard/phone alert) at the higher threshold.
• [Live PPM dashboard] The cloud dashboard shows a real-time concentration gauge, valve open/closed state, sensor warm-up status and a timestamped event log.
• [Student-run calibration] The alarm thresholds ship as starting values; the student sets final values with the included calibration procedure and documents the process — no claimed detection figures at build.
• [Valve self-test] A scheduled self-test pulses the valve to confirm it moves freely, with the result logged on the dashboard — stuck valves are the classic silent failure.
• [Manual reset with interlock] After an alarm, the valve reopens only on a deliberate manual reset after the concentration falls below the safe band.

• Working gas-leak detector prototype (ESP32, MQ-6, solenoid valve, buzzer, power supplies)
• Complete firmware source code (sensing, staging, valve control, dashboard sync)
• Live PPM dashboard setup with gauge, valve panel and event log
• Circuit and wiring documentation (including valve driver sizing)
• Burn-in and calibration procedure for threshold setting
• Component list with ratings
• Project report PDF (gas-sensor theory, safety logic, methodology, calibration results)
• PPT presentation for final review
• Viva Q&A preparation document (semiconductor sensors, fail-safe design, IoT alerting)
• Setup and demonstration guide

• This is an academic demonstration of leak detection and shutoff logic, not a certified gas-safety device; it must not be presented or installed as life-safety equipment — real installations need certified detectors fitted by qualified personnel.
• MQ-6 is a broad-spectrum semiconductor sensor: it responds to LPG but also to alcohol vapors, smoke and cooking fumes; cross-sensitivity is documented and the report must acknowledge it.
• Concentration readings are indicative (characteristic-curve estimates), not laboratory measurements; thresholds are relative trip points set by the student's own calibration.
• The sensor needs a warm-up/burn-in period before readings stabilize; cold-start readings are not valid and the firmware flags this state.
• The solenoid valve must be gas-line rated for the demo line used; the kit specifies the rating and the student must not substitute an unrated valve.