The MQ-3 Alcohol Sensor is a gas sensor specifically designed to detect alcohol vapors in the air. It is one of the most commonly used sensors for alcohol breath analyzers because it is highly sensitive to ethanol and has fast response times. 🔹 Details and Explanation 1. Main Features Type: Alcohol vapor sensor Gas Detected: Ethanol (alcohol), with some sensitivity to benzine, CH₄, LPG, CO Operating Voltage: 5V DC Current Consumption: 150 mA (approx.) Output: Analog (AO): Proportional to alcohol concentration Digital (DO): HIGH/LOW output (based on threshold set via potentiometer) Sensing Range: 0.05 mg/L – 10 mg/L alcohol in air 2. Working Principle The MQ-3 uses a tin dioxide (SnO₂) sensitive layer on an alumina substrate, with a heating element. In clean air → high resistance of SnO₂. In alcohol vapors → resistance decreases → higher current flow. This change is converted to a measurable voltage output. AO pin provides analog voltage that varies with alcohol concentration. DO pin provides a simple HIGH/LOW signal when alcohol level crosses the set threshold. 3. Pin Configuration (MQ-3 Module) VCC → +5V supply GND → Ground DO → Digital output (1 = alcohol detected, 0 = none) AO → Analog output (alcohol concentration level) 4. Applications Alcohol breath analyzers (portable breath tests) Drunk driving prevention systems (car ignition lock if alcohol detected) Workplace safety monitoring (factories, laboratories) IoT-based alcohol detection systems 5. Important Notes Needs preheating/burn-in time (24–48 hours) for stable readings. Works best with airflow exposure (not in closed air). Highly sensitive to ethanol but can also detect other gases slightly. Accuracy improves when using calibration in controlled alcohol concentrations.