The MQ-2 is a gas sensor sensitive to LPG, propane, hydrogen, methane, and smoke. It has both analog output (concentration level) and digital output (threshold trigger) on the module version. Requires a 24–48 hour burn-in period for stable readings.
| Pin | Name | Function | Type |
|---|---|---|---|
| VCC | VCC | 5V power supply | PWR |
| GND | GND | Ground | GND |
| DOUT | DOUT | Digital output, HIGH = gas detected | I/O |
| AOUT | AOUT | Analog output, higher = more gas | ADC |