Adafruit
AS7331 UVA/UVB/UVC Sensor Breakout
· MPN: ADA6476
This compact board makes it easy to measure ultraviolet light across three separate bands, giving you independent UVA, UVB and UVC readings instead of a sing...
This compact board makes it easy to measure ultraviolet light across three separate bands, giving you independent UVA, UVB and UVC readings instead of a single combined value. That makes it a strong fit for human and agricultural UV monitoring, as well as UVC-focused applications such as germicidal, curing, and other specialised sensing tasks.
The AS7331 is configurable over I2C, with multiple gain and conversion settings so you can tune it for different UV levels. Adafruit has also broken out the READY pin so you can tell when a conversion is complete, plus a SYNC input that can be used to synchronise readings with an external pulse.
To keep integration simple, the sensor is mounted on a STEMMA QT form factor breakout with onboard level shifting and SparkFun Qwiic compatible STEMMA QT connectors. That means you can plug it straight into a 3.3V or 5V microcontroller without needing to solder, and Adafruit provides both Arduino and CircuitPython libraries with example sketches to help you get started. A QT cable is not included.
Features:
- Three-band UV sensing: Reads and differentiates between UVA, UVB and UVC.
- Separate measurements: The three UV measurements are separated rather than mixed into one number.
- Configurable operation: Many gain and conversion settings are configurable over I2C.
- Address selection: The default I2C address can be changed using the two jumpers on the back.
- Multi-device support: You can have up to four sensors on the same bus.
- READY pin: Indicates when a sensor conversion is complete.
- SYNC input: Can be used to synchronise readings with an external pulse.
- STEMMA QT form factor: Mounted on a breakout board with SparkFun Qwiic compatible STEMMA QT connectors.
- Level shifting: Designed for use with 3.3V or 5V microcontrollers.
- Library support: Arduino and CircuitPython libraries are available.
- Examples included: Includes example sketches to help you get started.
Specifications:
- UVA channel measurement: up to 349 mW/cm² at 1x gain
- UVB channel measurement: up to 386 mW/cm² at 1x gain
- UVC channel measurement: up to 169 mW/cm² at 1x gain
- Responsivity: as low as 2.38 nW/cm² per LSB
- Interface: I2C
- Default I2C address: 0x74
- Address configuration: two jumpers on the back
- Maximum sensors per bus: up to four
- Logic compatibility: 3.3V or 5V microcontrollers
It suits Arduino, Raspberry Pi, and many CircuitPython-compatible boards, especially if you are already using the STEMMA QT or Qwiic ecosystem. If you need a cable for the QT connectors, it is sold separately.
Jargon buster
Plain-language definitions for the technical terms used above.
- AS7331
- A sensor chip designed to measure ultraviolet light in separate UVA, UVB and UVC bands. The part number matters because it tells you which libraries, datasheets and measurement capabilities apply to this breakout board.
- 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.
- CircuitPython
- A beginner-friendly version of Python designed to run directly on microcontroller boards. If a product supports CircuitPython, you can often program it by copying code files onto the board rather than setting up a more complex toolchain.
- 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.
- I2C address
- An I2C address is the number a device uses so a microcontroller can tell it apart from other devices on the same I2C bus. It matters because two devices with the same fixed address may conflict if used together.
- LSB
- Least significant bit is the smallest step a digital converter can represent. In a DAC, it tells you the tiniest voltage change the output can make at a given resolution and output range.
- 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.
- 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.
- READY pin
- A READY pin is a signal pin that changes state when the sensor has finished taking a measurement. It matters when your microcontroller needs to read data only after a fresh conversion is available, instead of guessing with delays.
- 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.
- SYNC input
- A SYNC input lets an external signal trigger or align the timing of sensor readings. This matters when measurements need to be coordinated with another device, pulse, light source or experiment timing.
- UVA
- UVA is the longer-wavelength part of ultraviolet light, closest to visible violet light. Measuring it separately matters when you need to distinguish general UV exposure from the more energetic UVB and UVC bands.
- UVB
- UVB is a middle band of ultraviolet light that is more energetic than UVA and is important in sun exposure and plant-related UV monitoring. A sensor with a separate UVB channel lets you measure this band without it being mixed together with other UV light.
- UVC
- UVC is a short-wavelength, high-energy band of ultraviolet light often used in germicidal lamps and curing applications. A separate UVC reading matters if your project needs to monitor or verify UVC sources rather than just detect general UV light.
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Sensors & Input
AS7331 Datasheet
Datasheet · 2.2 MB · Click any page to view full size
Supplier page — adafruit.com
Supplier Description · 1.1 MB · Click any page to view full size
