The MQ-3 Gas Sensor Module is a low-cost, semiconductor-based sensor specialized for detecting alcohol (ethanol) vapor in the air. It functions primarily as a breathalyzer component, utilizing a Tin Dioxide (\(SnO_{2}\)) sensing element that changes electrical resistance based on gas concentration. Key Technical Specifications

• Operating Voltage: 5V DC.
• Current Consumption: ~150 mA (due to internal heater).
• Detection Range: 0.04 mg/L to 4 mg/L (approximately 25 to 500 ppm).
• Output Signal Type: Dual output (Analog and Digital TTL).

Module Pinout ConfigurationThe sensor break-out board typically features 4 output interface pins:

• VCC: Connects to the 5V power supply line of the microcontroller.
• GND: Connects to the system common ground.
• DO (Digital Output): Emits a TTL digital signal (HIGH/LOW). Trigger threshold is adjusted manually via the onboard potentiometer.
• AO (Analog Output): Outputs a continuous voltage gradient ranging from 0.1V to 4V. The voltage increases linearly relative to the detected ethanol concentration.