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Adafruit SGP40 Air Quality Sensor Breakout - VOC Index - STEMMA QT / Qwiic
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The Adafruit SGP40 is a next-generation MOX (metal-oxide) gas sensor from Sensirion for indoor air quality monitoring. Unlike its predecessor the SGP30, the ...
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The Adafruit SGP40 is a next-generation MOX (metal-oxide) gas sensor from Sensirion for indoor air quality monitoring. Unlike its predecessor the SGP30, the SGP40 outputs a raw signal that is processed through Sensirion's VOC algorithm to produce an overall air quality index from 0 to 500 — rather than separate TVOC and eCO2 values.
The sensor combines multiple metal-oxide sensing and heating elements on a single chip with a built-in microcontroller that manages the heater, reads analog voltages, and provides an I2C interface. No I2C clock stretching is required.
Key Features
- VOC Index Output – Processed air quality score from 0 to 500 via Sensirion's algorithm
- Wide VOC Detection – Detects a broad range of volatile organic compounds and H2
- Humidity Compensation – Accept external humidity data over I2C for improved accuracy
- I2C Interface – No clock stretching required; STEMMA QT / Qwiic connectors for solderless hookup
- 3.3 V / 5 V Compatible – Onboard 3.3 V regulator and level shifting
- Next Generation – Successor to the SGP30 with improved sensing architecture
Note: The SGP40 does not output TVOC or eCO2 values like the SGP30. Instead, it provides a VOC index (0–500) processed through Sensirion's algorithm. Like all VOC/gas sensors, calibration against known sources is recommended for precise measurements. Arduino library available; Python support is not yet available.
Also Consider
- SGP30 Air Quality Sensor – Previous generation with direct TVOC and eCO2 output values
- SCD-40 True CO2 Sensor – Direct photoacoustic CO2 measurement (400–2,000 ppm)
Ideal For
- Indoor air quality monitoring and trend detection
- Smart ventilation triggering
- Environmental sensing projects
- VOC detection in homes and offices
Package Contents
- 1× Adafruit SGP40 Air Quality Sensor Breakout
Tip: STEMMA QT / Qwiic cable is not included. Pair with an external humidity sensor (like the SHT40 or SHT45) for humidity-compensated readings and improved accuracy.
Resources
Jargon buster
Plain-language definitions for the technical terms used above.
- breakout
- A breakout is a small circuit board that makes a tiny or hard-to-solder component easier to connect to with standard pins. It matters because this OLED module can be wired into a microcontroller project without needing to solder directly to the display’s fine contacts.
- I2C
- I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
- microcontroller
- A microcontroller is a small computer on a chip that runs your program and controls connected inputs and outputs. For this product, it is the part that reads buttons and sensors, drives the display and speaker, and communicates over Bluetooth.
- ppm
- ppm means parts per million, a common way to express very small gas concentrations in air. For CO₂ sensors, the ppm range tells you what levels the sensor can measure, such as normal indoor air through to poorly ventilated spaces.
- Qwiic
- Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.
- SHT40
- SHT40 is a Sensirion temperature and humidity sensor included on the module. It matters because the board can report room temperature and humidity as well as use those readings to improve the CO₂ measurement.
- STEMMA
- A plug-and-cable connection system used on some maker electronics boards to make wiring simpler. If a product uses STEMMA, you need the matching cable or connector type to plug it in without soldering.
- STEMMA QT
- A small plug-in connector system for I2C boards that lets you connect compatible sensors and controllers without soldering. It matters because it can make wiring faster and less error-prone, especially when adding several small modules to a project.
- VOC
- Volatile organic compounds are gases released from things like paints, cleaners, smoke, and some plastics. A VOC reading helps indicate indoor air quality, but it is usually an index or estimate rather than a direct identification of each chemical.
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