Description

Visible model: MQ-3.
Sensing principle: Tin-oxide semiconductor whose conductivity changes with alcohol exposure.
Visible connections: VCC, GND, DO (digital output) and AO (analog output).
Adjustment: Visible trimmer, typically used to set the digital detection threshold.
Construction: Orange sensor housing with a mesh opening on a blue PCB with mounting holes.
Potential applications: Alcohol-vapor detection, educational projects and threshold-alarm prototypes.