Smart Miner Safety Helmet with Gas Detection and Emergency Beacon

Underground miners work where the air itself is the danger: methane can accumulate to explosive concentrations, carbon monoxide from machinery and blasting can poison without warning, and rock falls or slips can injure a worker beyond anyone's sight or hearing. Certified mine-safety systems exist but are expensive, complex and out of reach for a college lab. This project builds a working educational prototype of an IoT miner safety helmet — a standard safety-helmet shell carrying an MQ-4 methane sensor, an MQ-7 carbon monoxide sensor, a DHT22 temperature-humidity sensor, an ADXL345 impact sensor, an ESP32 controller and a LoRa radio. On board, a buzzer, flashing LED beacon and the helmet cap-lamp give immediate local warnings; remotely, a LoRa SOS packet carrying the miner's programmed ID reaches a base-station receiver at the surface side of the tunnel. Because cellular networks do not penetrate rock, LoRa's long-range sub-GHz link is the right wireless choice for this environment. This is strictly an educational prototype for demonstrating sensing, threshold logic, low-power wireless and embedded safety design — it is not a certified life-safety device.

1. The buyer runs the documented burn-in and clean-air calibration for the MQ-4 and MQ-7, storing baseline voltages and alarm thresholds in ESP32 flash via the calibration mode.
2. On power-up, the ESP32 initializes the sensors, starts the MQ-7 pulsed high/low heater cycle per its datasheet, and registers the miner ID programmed for that helmet.
3. Gas sampling runs continuously: MQ-4 and MQ-7 readings are converted to ppm with the calibration curve and compared against methane and CO alarm thresholds.
4. The ADXL345 is polled for acceleration spikes; a spike exceeding the impact threshold is treated as a fall or strike event, with a short confirmation window to reject ordinary bumps.
5. On a gas or impact event, the firmware drives the buzzer, flashes the LED beacon and ramps the cap-lamp brightness for local warning.
6. Simultaneously, the ESP32 builds a LoRa packet (miner ID, event type, latest gas values) and transmits it to the base-station receiver, which logs it over USB serial with a timestamp.
7. The DHT22 is sampled periodically; if temperature and humidity stay above the heat-stress setpoints for the configured duration, a separate heat alert is raised on the helmet and the radio.

Tech stack:

• ESP32
• MQ-4 methane sensor · 200–10000 ppm datasheet range
• MQ-7 CO sensor · pulsed heater cycle
• DHT22 temperature · humidity sensor
• ADXL345 3-axis accelerometer
• LoRa SX1278 · 433 MHz
• Arduino framework
• 18650 Li-ion · TP4056 charger

• [Methane and carbon monoxide sensing] An MQ-4 sensor watches for methane (datasheet detection range 200–10000 ppm) and an MQ-7 watches for carbon monoxide (datasheet range 10–500 ppm), both mounted on the helmet shell near breathing height. When readings cross the buyer-calibrated alarm thresholds, the buzzer and red LED fire immediately.
• [Impact detection with automatic SOS] The ADXL345 accelerometer (±16g full-scale range, per datasheet) monitors for falls and hard impacts. A spike past the firmware threshold raises the local alert and automatically transmits a LoRa SOS packet carrying the miner's programmed ID to the base station.
• [LoRa emergency link for underground use] A 433 MHz LoRa module (SX1278) carries short SOS packets to a base-station receiver — no cellular or Wi-Fi needed. Usable tunnel range is a design target of a few hundred metres, site-dependent; rock and tunnel bends reduce it, and repeaters are listed as future scope.
• [Heat-stress monitoring] A DHT22 tracks temperature and humidity around the helmet (±0.5°C and ±2% RH, per datasheet). Sustained high heat-humidity readings raise an alert, flagging ventilation checks before heat exhaustion sets in.
• [Cap-lamp, buzzer and LED beacon outputs] The ESP32 drives the helmet cap-lamp with PWM dimming, a loud buzzer and a flashing LED beacon, so warnings remain visible and audible in dark, noisy tunnel conditions.
• [Documented gas-sensor calibration procedure] MQ sensors need burn-in and clean-air calibration before their readings mean anything. The firmware exposes a calibration mode and the kit documents the full procedure — the buyer runs it on receipt; nothing ships pre-calibrated and no accuracy is claimed without it.
• [Base-station receiver with serial dashboard] A matching LoRa receiver board (included) forwards SOS and status packets to a PC over USB serial, logging miner ID, gas values, impact events and timestamps for the surface operator's display.

• Sensor-fitted miner safety helmet prototype (MQ-4, MQ-7, DHT22, ADXL345, ESP32, LoRa module, buzzer, LED beacon, cap-lamp, battery)
• Matching LoRa base-station receiver board with USB-serial logging
• ESP32 firmware with gas calibration mode (Arduino framework source)
• Wiring diagram and sensor mounting guide
• Gas-sensor burn-in and calibration procedure document
• Project report PDF (background, design, methodology, honest scope notes)
• PPT presentation for final review
• Viva Q&A preparation document (gas sensors, LoRa, impact detection, calibration)

• This is an educational prototype, NOT a certified mine-safety device — it must never be used in a real mine or relied on for actual worker safety.
• MQ-4 and MQ-7 are semiconductor gas sensors with cross-sensitivity (alcohol vapour, smoke, other hydrocarbons shift readings); their readings are indicative, never life-safety measurements.
• LoRa reach underground is a design target of a few hundred metres; rock composition, bends and conductive ore cut it sharply — on-site range testing is part of the build, not an assumption.
• The MQ-7 needs its datasheet's alternating high/low heater-voltage cycle for CO sensing; the firmware implements it, but readings remain indicative, not analytical-grade.
• Alarm thresholds ship unset — the buyer must run the documented calibration procedure; detection claims only hold after that procedure is completed.
• Dropping the helmet itself can exceed the impact threshold and trigger a false SOS; the confirmation window reduces but does not eliminate this.
• Expected battery runtime is ~8–12 h; full-brightness cap-lamp use pulls it toward the lower end, and 18650 capacity varies by cell.