MQ-3 Alcohol-Ethanol Sensor

MQ-3 Alcohol Gas Sensor
The sensor uses a Tin Dioxide (SnO_2) sensing layer. When alcohol vapours come into contact with the heated sensing element, a chemical reaction occurs that releases electrons, decreasing the sensor's internal resistance. The more alcohol present, the lower the resistance and the higher the output voltage.

Why it’s the Choice for Breathalyzers:
• High Ethanol Specificity: While it can react to other gases, the MQ-3 is tuned specifically to be most sensitive to alcohol, making it much more accurate for sobriety-related projects than a general-purpose MQ-2.
• Dual Output Utility:
* Analog (A0): Essential for breathalysers. It provides a variable voltage that you can map to BAC (Blood Alcohol Content) or mg/L concentrations.
* Digital (D0): Perfect for safety interlocks. For example, it can trigger a relay to prevent a motor from starting if alcohol is detected in a cabin.
• Fast Recovery: After a "positive" test, the sensor clears itself relatively quickly, allowing for a new test once the alcohol vapours have dissipated from the sensor chamber.

Technical Capabilities:
• Detection Concentration: 0.05 mg/L to 10 mg/L of alcohol.
• Operating Voltage: 5V (Required for the internal heater).
• Sensitivity Adjustment: The onboard potentiometer allows you to set the digital threshold, which is useful for creating a "Pass/Fail" indicator light.

Best For:
The MQ-3 is the primary sensor for portable breathalysers, alcohol-ignition interlock prototypes, distillery safety monitors, and environmental alcohol vapor sensing.