MQ-2 Smoke & Flammable Gas Sensor Module - LPG, Propane, Hydrogen Detector

Specifications

• Sensor Type: MQ-2 (SnO2 Semiconductor)

• Target Gases: LPG, Propane, Hydrogen, Methane, Smoke, Alcohol, Butane

• Detection Range: 300 ppm – 10,000 ppm

• Operating Voltage: 5V DC ±0.1V

• Heater Consumption: ~800mW (Requires stable power)

• Outputs:

  • Analog (AO): 0V to ~5V (Voltage increases with gas concentration)

  • Digital (DO): TTL Logic (Low/High) adjustable via onboard potentiometer

• Response Time: < 10 seconds

• Recovery Time: < 30 seconds

Key Applications

• Home Safety: LPG gas leakage detectors for kitchens.

• Industrial Safety: Hydrogen leak monitoring in battery charging stations.

• Fire Automation: Triggering sprinklers or exhaust fans upon smoke detection.

• Robotics: Fire-fighting robots that track smoke sources.

Project Evolution

From Blinking LEDs to Life-Saving Automation If you have learned how to read a potentiometer or a button state, you are ready for the MQ-2.

• The Upgrade: Build a Smart Kitchen Guard. Instead of just buzzing a simple alarm, connect this to a 5V Relay Module. When gas is detected, your system can automatically shut off an electric solenoid valve or turn on an exhaust fan.

• Effort Level: Beginner to Intermediate. Reading the sensor is easy; calibrating the alarm threshold takes some experimentation.

• Hardware Needed: Arduino Uno/Nano, Active Buzzer, and a 5V Power Supply (Gas sensors are power-hungry!).

Virtual Technician: Wiring & Safety

Critical Warning: The MQ-2 has an internal heater that gets warm to the touch. This is normal! Do not touch the mesh while powered. Also, never expose the sensor to pure silicone vapors or corrosive gases, as they will permanently damage the sensitive layer.

Pin Mapping (Standard):

• VCC: 5V DC (Do not use 3.3V, the heater won't work)

• GND: Ground

• D0 (Digital): Connect to any Digital Pin (High/Low trigger)

• A0 (Analogue): Connect to Analogue Pin (A0-A5) for precise readings

Wiring Tip: If using an ESP32 (3.3V Logic), you must use a voltage divider on the Analogue Output (AO) to bring the 5V signal down to 3.3V to protect your board.

Accessories & Compatibility

• Included: 1x MQ-2 Smoke & Flammable Gas Sensor Module

• Compatible: Arduino, ESP32.

Technical FAQs:

• What gases can the MQ-2 detect? It is most sensitive to LPG, Propane, and Hydrogen. It also detects Methane (Natural Gas), Smoke, Butane, and Alcohol to a lesser degree.
• Why does the sensor get hot? The sensor contains a micro-heater that must reach a specific temperature to chemically react with the gas. It is normal for the module to feel warm (approx. 40°C-50°C).
• What is the "Pre-heat" time? When you first power it up after storage, the readings will be erratic for about 24-48 hours. For accurate calibration, let it "burn in" (stay powered) for at least 24 hours. For quick testing, wait 5 minutes after power-up.
• How do I adjust the Digital Output sensitivity? There is a blue potentiometer on the back. Turn it until the LED indicator turns off in clean air. Blow some gas near it; the LED should turn on. Adjust the screw to set your trigger threshold.
• Can I use this with a 3.3V Raspberry Pi or ESP32? The sensor requires 5V to heat up. However, the Digital Output is usually compatible with 3.3V if powered by 5V. For the Analog Output, you MUST use a voltage divider or logic shifter to lower the 5V signal to 3.3V.
• Does it tell me exactly which gas it found? No. The MQ-2 is non-specific. It outputs a higher voltage for any combustible gas or smoke. It cannot tell you "This is LPG" vs "This is Smoke" if both are possibilities.
• What is the range in ppm? It detects concentrations from 300 ppm to 10,000 ppm.
• Can I use this to detect Carbon Monoxide (CO)? No. While it might react slightly, it is not designed for CO. Use an MQ-7 sensor for Carbon Monoxide detection.
• How do I convert the Analog voltage to ppm? This requires complex math involving the sensor's resistance curve (Rs/R0) found in the datasheet. Most hobbyists simply use raw values (0-1023) to set a threshold relative to clean air.
• Is the module waterproof? No. Water or high humidity condensation will short the heater and ruin the chemical layer.
• Why is the LED always on? The sensitivity is likely set too high. Turn the potentiometer counter-clockwise until the LED turns off.
• Can I use a battery to power it? You can, but the heater draws ~150mA continuous current. A standard 9V battery will drain very quickly. Use a Li-Ion pack or a wall adapter.
• What happens if I connect VCC and GND backwards? This will likely damage the internal circuit or the comparator chip. Always double-check polarity.
• What is the difference between MQ-2 and MQ-5? MQ-2 is a general-purpose combustible gas/smoke sensor. MQ-5 is specifically optimized for LPG and Natural Gas with very low sensitivity to smoke/alcohol, making it better for kitchen false-alarm prevention.
• Can it detect cigarette smoke? Yes, it is quite sensitive to the particulates and gases in cigarette smoke.
• How long does the sensor last? Under normal conditions, the sensor life is about 4-5 years.
• What is the "clean air" voltage reading? In clean air, the analog voltage is usually low (0.1V - 0.5V). When gas is present, it rises rapidly towards 5V.
• Does airflow affect readings? Yes. Strong wind can cool the heater, causing the readings to drop. Place the sensor in a shield if used in a windy environment.
• Can I use the Digital and Analog pins at the same time? Yes. You can use the Digital pin for a quick "Alarm" interrupt and the Analog pin for logging data levels simultaneously.
• Is this sensor calibrated out of the box? No. All gas sensors vary slightly. You must calibrate your code's threshold based on the specific sensor's reading in your clean air environment.