MQ-2 Smoke and Flammable gas

The MQ-2 Gas Sensor Module is one of the most popular and cost-effective gas detection sensors used in DIY electronics, home safety projects, and educational experiments. It is designed to detect a wide variety of flammable gases and smoke, making it an essential component for any fire safety, gas leak monitoring, or air quality system.

The heart of the module is the MQ-2 sensor, which uses Tin Dioxide (SnO₂) as its sensitive material. In clean air, SnO₂ has relatively low conductivity. However, when combustible gases (such as LPG, propane, methane, hydrogen, alcohol, or smoke) are present, the sensor's conductivity increases proportionally with the gas concentration. This change in conductivity is converted into an analog voltage signal that can be read directly by a microcontroller's ADC pin.

The module integrates an LM393 voltage comparator, which adds a digital output (DOUT) triggered when the gas concentration crosses a user-defined threshold (adjustable via the onboard multi-turn potentiometer). This means the MQ-2 module can be used in two modes simultaneously:

• Analog Output (AO) — for precise gas concentration measurement
• Digital Output (DO) — for simple ON/OFF threshold-triggered alarms

The module also includes a power LED and a status/threshold LED, making it easy to test and visualize sensor activity. With its standard 4-pin interface (VCC, GND, DO, AO) and 2.54mm pitch goldpin connectors, the module connects effortlessly to Arduino, ESP32, ESP8266, STM32, Raspberry Pi, and PIC microcontrollers.

Note: The MQ-2 sensor requires a preheating period of 24–48 hours when first powered on to deliver accurate and stable readings.

Specifications

• Sensor Model: MQ-2
• Comparator IC: LM393
• Power Supply: 5V DC
• Current Consumption: ~150 mA (heater active)
• Detection Range: 300 – 10,000 ppm (depending on gas type)
• Detected Gases: LPG, Propane, Methane, Hydrogen, Alcohol, Smoke, CO
• Operating Temperature: -20°C to +50°C
• Output Type: Analog (AO) + Digital (DO)
• Onboard Pull-down Resistor: 1 kΩ (sensor output to GND)
• Sensitivity Adjustment: Onboard multi-turn potentiometer
• Connector Pitch: 2.54 mm (Standard Goldpin Headers)
• Board Dimensions: 36 × 20 × 23 mm
• Mounting Hole Diameter: 3.2 mm
• Pinout: VCC, GND, DO (Digital Out), AO (Analog Out)
• Compliance: RoHS Compliant

Applications

• Smoke Alarms & Fire Detection — early warning systems for homes and offices
• Gas Leak Detectors — LPG, propane, and methane leak monitoring in kitchens
• Industrial Safety Monitoring — combustible gas detection in workshops
• Home Automation Systems — automated alerts and exhaust fan control
• Air Quality Monitoring — indoor pollutant tracking with Arduino/ESP32
• Vehicle Cabin Safety — alcohol and fuel vapor detection
• Educational & STEM Projects — teaching gas sensing and signal processing
• IoT Smart Home Projects — gas alerts via WiFi to smartphones
• Garage & Boiler Room Monitoring — early detection of fuel/gas leaks
• Greenhouse & Agriculture Monitoring — combustible gas tracking
• Camping & Caravan Safety — gas leak alerts in mobile environments
• Boat & RV Safety Systems — flammable vapor detection
• DIY Arduino Projects — sound, light, and SMS-based gas alarms
• Replacement Sensor — for damaged or aging MQ-2 modules