Alcohol Gas Sensor MQ-3

This semiconductor petrol sensor detects the presence of alcohol petrol at concentrations from 0.04 mg/L to 4 mg/L, a range suitable for making a breathalyser. The sensor’s simple analogue voltage interface requires only one analogue input pin from your microcontroller.


Our supplier is out of stock

Our Code: SKU-002705

Supplier Link: [Pololu MPN:1634]


Pololu - Gas sensor with orange plastic case with quarter for size reference


This alcohol petrol sensor detects the concentration of alcohol petrol in the air and ouputs its reading as an analogue voltage. The concentration sensing range of 0.04 mg/L to 4 mg/L is suitable for breathalysers (the legal limit of breath alcohol concentration, or BrAC, in most US states is 0.08 grams per 210 liters, or 0.38 mg/L). The sensor can operate at temperatures from -10 to 50°C and consumes less than 150 mA at 5 V. Please read the MQ3 datasheet (153k pdf) for more information about the sensor.

Gas sensor with orange plastic case bottom view


Connecting five volts across the heating (H) pins keeps the sensor hot enough to function correctly. Connecting five volts at either the A or B pins causes the sensor to emit an analogue voltage on the other pins. A resistive load between the output pins and ground sets the sensitivity of the detector. Please note that the picture in the datasheet for the top configuration is wrong. Both configurations have the same pinout consistent with the bottom configuration.The resistive load should be calibrated for your particular application using the equations in the datasheet, but a good starting value for the resistor is 200 kΩ.

We offer two breakout boards that make it easier to interface with these sensors: a Pololu carrier board and a SparkFun carrier board. The Pololu version is shown below.

Pololu MQ gas sensor carrier with sensitivity-setting resistor soldered in the vertical orientation

Note: These sensors could have orange or blue plastic cases. There is no functional difference between the two coloured cases.

Pololu - Gas sensor with orange plastic case

Gas sensor with blue plastic case


File downloads

Alcohol petrol sensor MQ-3 datasheet (153k pdf)

Recommended links

Blood alcohol content
Wikipedia’s page on blood alcohol content (BAC) and breath alcohol content (BrAC).