The MQ-7 is a Carbon Monoxide (CO) Gas Sensor designed to detect the presence of CO gas in air. It is widely used in gas leakage detection systems and safety devices because carbon monoxide is a toxic, colorless, odorless gas that poses serious health risks. 🔹 Details and Explanation 1. Main Features Type: Carbon Monoxide (CO) gas sensor Gas Detected: Carbon Monoxide (CO), with slight sensitivity to hydrogen, LPG, methane Operating Voltage: 5V DC Current Consumption: 150 mA (approx.) Output: Analog (AO): Continuous signal proportional to CO concentration Digital (DO): HIGH/LOW output based on threshold set via onboard potentiometer Detection Range: 20 ppm – 2000 ppm of CO 2. Working Principle The sensor has a heating element and a SnO₂ (tin dioxide) semiconductor layer. In clean air → resistance of SnO₂ is high. In the presence of CO → resistance decreases → current increases. This variation is converted into a voltage signal on the output pins. AO pin gives analog readings of CO concentration. DO pin goes HIGH when CO concentration exceeds the preset threshold. 3. Pin Configuration (MQ-7 Module) VCC → +5V supply GND → Ground DO → Digital output (1 = CO detected, 0 = no CO) AO → Analog output (proportional to CO level) 4. Special Feature of MQ-7 MQ-7 works in a cyclic heating mode: Requires high temperature (~5V heating for 60 sec) to clean the sensor. Requires low temperature (~1.4V heating for 90 sec) for sensing CO. This makes it different from MQ-2, MQ-3, and other sensors, which use continuous heating. 5. Applications Carbon monoxide detectors in homes and industries Fire detection systems (detecting CO in smoke) Vehicle exhaust monitoring IoT-based safety systems Portable CO alarms for miners, workers, and households 6. Important Notes Needs burn-in time (24–48 hours) before stable use. Should not be used as a precision medical device—better suited for safety monitoring. Works best with proper cyclic heating control for accurate CO measurement.