MQ Gas Sensors – Hardware details

Pinout

Native version

Click here for a high-resolution image of the pinout.

ℹ️

While the pinout shown is for the MQ135, it is exactly the same for any Native MQ sensor

Pin Marking	Pin Name	Description
5V	Power	Supply voltage for the sensor
DO	Digital Output	Set to HIGH when sensor reads gas concentration over the trigger level set by the onboard potentiometer
AO	Analog Output	Voltage output proportional to gas measurement
GND	Ground	Common ground for power and signals.

Qwiic version

Click here for a high-resolution image of the pinout.

ℹ️

While the pinout shown is for the MQ8, it is exactly the same for any Qwiic MQ sensor

Pin Marking	Pin Name	Description
3V3	Power	Supply voltage for the UPDI
UPDI	UPDI	Communication pin for UPDI
GND	Ground	Common ground for power and signals.

⚠️

UPDI stands for Unified Program and Debug Interface. It is used to program and debug Atmel devices. The atmel chip on this board is used for the easyC I2C communication only. DO NOT try to use this for sensor communication!

ℹ️

This board is fully Qwiic-compatible! Just plug it into your board using a Qwiic/easyC/STEMMA QT cable and start coding!

Qwiic (formerly easyC) details and specifications

Learn about hardware specifications, compatibility, and usage of the Qwiic connector.

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Dimensions

Native

• Board Dimensions: 22 x 38 mm (0.9 x 1.5 inches)
• Header Pin Holes: 1.5 mm
• Screw Holes: Designed for M3 screws (3.2 mm diameter)
• Soldered boards are LEGO-compatible! 🧱

Qwiic

• Board Dimensions: 54 x 22 mm (2.1 x 0.9 inches)
• Header Pin Holes: 1.5 mm
• Screw Holes: Designed for M3 screws (3.2 mm diameter)
• Soldered boards are LEGO-compatible! 🧱

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Jumper Details (Qwiic version)

This board contains hardware jumpers. See below for their locations and functions:

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Jumper	Default State	Function
JP1	NC (Normally closed)	Connects SDA/SCL pull-up resistors to 5V for I2C communication.
JP2	NC (Normally closed)	Connects SDA/SCL pull-up resistors to 3.3V for I2C communication.

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Address selection (Qwiic version)

This board contains hardware address switches. See below for instructions on changing the breakout board's address:

Address	SW3	SW2	SW1
0x30	0	0	0
0x31	0	0	1
0x32	0	1	0
0x33	0	1	1
0x34	1	0	0
0x35	1	0	1
0x36	1	1	0
0x37	1	1	1

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Hardware repository

In the link below, you can find repositories of hardware designs for all MQ sensor types, which include Schematics, KiCad files, Gerber files and more:

MQ Sensors Hardware Design

GitHub hardware repositories for all MQ sensors

The hardware repository contains everything you need to understand, modify, or manufacture the board. The different output folders are versioned. You can determine your board version by checking the version mark on the PCB.

Below is an overview of the available files.

CAD files

We use KiCad, an open-source PCB design tool. You can open and edit the .kicad_pro project file, which includes both the schematic and PCB layout.

The PANEL files are used internally for production.

Schematic

The OUTPUTS folder contains the schematic in .pdf format, exported from KiCad.

BOM (Bill of Materials)

The bill of materials (BOM) is provided in two formats:

• A standard .csv table, listing all components, part numbers, and values.
• An interactive BOM (.html) that visually highlights each component on the PCB, making it easy to locate and reference parts.

3D files

A 3D model of the PCB is available in .step format, allowing you to inspect the board design in CAD software.

Gerber files

Gerber files are essential for PCB manufacturing, as they contain precise instructions for each layer of the board. The repository includes standard Gerber outputs in a .zip file, such as:

• Copper layers (.Cu.gbr) – Defines the traces and pads on the board.
• Solder mask layers (.Mask.gbr) – Specifies the protective solder mask.
• Silkscreen layers (.Silkscreen.gbr) – Contains text and component markings.
• Paste layers (.Paste.gbr) – Used for stencil fabrication in SMD assembly.
• Drill files (.drl) – Provides drilling coordinates for vias and holes.
• Board outline (.Edge_Cuts.gbr) – Defines the shape of the PCB.
• Gerber job file (.gbrjob) – Describes the set of Gerber files used for production.

These files are ready for fabrication and can be used in PCB manufacturing.

Compliance

The Compliance section includes important regulatory and safety documentation for this product. These files ensure compliance with relevant industry standards and legal requirements.

• CE – Certification document confirming compliance with EU safety, health, and environmental requirements.
• UKCA – UKCA (UK Conformity Assessed) certification for the UK market.
• Safety Instructions – Safety guidelines and precautions in English and in German.
• Info.txt – Contains product details such as SKU, country of origin, HS tariff code, and barcode.