9530 – MQ-3 Gas Sensor/en

Documentation notice: This technical documentation was independently rewritten from an archived supplier source. Check technical details and commands against the product version and manufacturer documentation before use.

Summary

The MQ-3 is a tin-oxide based gas sensor that is primarily sensitive to alcohol and ethanol. It provides an analog output (AOUT) and a digital threshold output (DOUT), whose sensitivity can be adjusted via a potentiometer.

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Technical overview

Sensing material: tin dioxide (SnO2); conductivity increases as the concentration of alcohol vapor in the air rises.
Power supply: 2.5 V to 5.0 V; the Pico example uses 3.3 V, the Arduino example uses 5 V.
Dimensions: 40.0 mm x 21.0 mm; mounting hole diameter 2.0 mm.
Pinout: DOUT (digital data output), AOUT (analog data output), GND (ground), VCC (power input).
Pico connection: VCC to 3.3 V, GND to GND, AOUT to GP26, DOUT to GP22.
STM32 connection (F103RB): VCC to 3.3 V, GND to GND, AOUT to PA6, DOUT to PA4.
Arduino UNO connection: VCC to 5 V, GND to GND, AOUT to A0, DOUT to D2.
Preheat time: The sensor needs about one minute to heat the internal sensing material.
Behavior: When the target gas is present, the module indicator LED lights up; it turns off once the sensor is removed.

Commands and examples – verify before use:

sudo apt-get install p7zip-full
cd ~
sudo wget https://files.waveshare.com/upload/1/13/MQ-3-Gas-Sensor-code.7z
7z x MQ-3-Gas-Sensor-code.7z -o./MQ-3-Gas-Sensor-code
cd ~/MQ-3-Gas-Sensor-code
cd Pico/c/build/
cd ~/MQ-3-Gas-Sensor-code/Pico/c/
cd build
export PICO_SDK_PATH=../../pico-sdk
cmake ..
make -j9
cp main.uf2 /media/pi/RPI-RP2/

Notes and version constraints

The provided examples are based on specific boards (Pico, STM32F103RBT6/H743, Arduino UNO). For other boards, connections and code may need to be adapted or ported.
The exact firmware version for the Pico (rp2-pico-20210418-v1.15.uf2) is version-sensitive; compatibility with newer Pico variants must be verified.
The preheat time of about one minute is a guideline; it may vary with ambient temperature.
The instruction “make -j9” applies to standard Pi; for a Pi Zero, only “make” should be run, as noted in the source.
The source contains no information about certifications, warranty, or safety standards – no such claims are made.

Source and revision record

MQ-3 Gas Sensor - Waveshare Wiki
Source revision: 68939
Captured: 2026-08-29T09:41:17+00:00
SHA-256: 7ae04700381d06690eab1205822d40222136a19a4cd38a6f018d1c4526713069