# Adafruit AS7331 UV / UVA / UVB / UVC Sensor
## Overview
The **Adafruit AS7331 UVA / UVB / UVC Sensor Breakout** is a perfect solution to UV sensing, no matter what 'type' you're sensing. Most UV sensors do just UVA, maybe ambient light too. But the AS7331 can read and differentiate between all the three bands. That means you can use it for human and agricultural UV alerts that tend to focus on UVA and UVB as well as agricultural, germicidal, curing, and other UVC use cases. We particularly like that the three measurements are separated, not just mixed together into one number.
The AS7331 has many gain and conversion settings configurable over I2C which means you can measure up to 349 mW/cm² on UVA channel, 386 mW/cm² on UVB and 169 mW/cm² on UVC at 1x gain, and with a responsivity as low as 2.38 nW/cm² per LSB.
In addition to the basic I2C connection, there's also the ability to change the default I2C address from 0x74 using the two jumpers on the back so you can have up to four sensors on the same bus. We also break out the READY pin that will let you know when a sensor conversion is complete, and the SYNC input, which can be used to synchronize the readings with an external pulse.
To make it easy to use, we mounted the tiny sensor on a STEMMA QT form factor breakout board, complete with level shifting circuitry and [SparkFun Qwiic](https://www.sparkfun.com/qwiic) compatible [Stemma QT](https://learn.adafruit.com/introducing-adafruit-stemma-qt) connectors. This means that you can, without needing to solder, connect our AS7331 breakout into your 3.3V or 5V microcontroller of choice be it an Arduino Uno, Raspberry Pi, or one of the many [CircuitPython-compatible boards](https://circuitpython.org/downloads).
Our Arduino and CircuitPython libraries make it easy to configure the AS7331 over I2C, with many included example sketches to help get you started. [**QT Cable is not included** , but we have a variety in the shop](https://www.adafruit.com/?q=stemma+qt+cable&sort=BestMatch).
# Adafruit AS7331 UV / UVA / UVB / UVC Sensor
## Pinouts
The default I2C address is **0x74**.
## Power Pins
- **VIN** - this is the power pin. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V microcontroller like Arduino, use 5V. For a 3.3V microcontroller, use 3.3V.
- **GND** - common ground for power and logic.
## I2C Logic Pins
- **SCL**** **- I2C clock pin, connect to your microcontroller I2C clock line. This pin is level shifted so you can use 3-5V logic, and there's a ** 10K pullup** on this pin.
- **SDA**** **- I2C data pin, connect to your microcontroller I2C data line. This pin is level shifted so you can use 3-5V logic, and there's a ** 10K pullup** on this pin.
- **[STEMMA QT](https://learn.adafruit.com/introducing-adafruit-stemma-qt) - **These connectors allow you to connect to dev boards with **STEMMA QT** connectors or to other things with [various associated accessories](https://www.adafruit.com/?q=JST%20SH%204).
## Other Pins
- **SYNC** - The **SYNC** pin is an input that can trigger synchronous readings from the AS7331 with an external pulse.
- **RDY** - The data ready pin can be configured as push-pull or open drain in software to alert you when a sensor conversion is complete.
## Address Jumpers
On the back of the board are two **address jumpers** , labeled **A0** and **A1**. These jumpers allow you to chain up to 4 of these boards on the same pair of I2C clock and data pins. To do so, you solder the jumper "closed" by connecting the two pads.
The default I2C address is **0x74**. The other address option can be calculated by “adding” **A0** and/or **A1** to the base of **0x74**.
For example, if **A1** is soldered closed and **A**** 0 ** is soldered closed, the address is ** 0x74 + 2 + 1 = 0x77**.
If only **A**** 0 ** is soldered closed, the address is ** 0x74 + 1 = 0x75**
If only **A1** is soldered closed, the address is **0x74 + 2 = 0x76**
The table below shows all possible addresses, and whether the jumper(s) should be high (closed) or low (open).
## Power LED and Jumper
- **Power LED -** In the upper left corner, above the STEMMA QT connector, on the front of the board, is the power LED, labeled **on**. It is a green LED.
- **LED jumper ** - This jumper is located on the back of the board and is labeled **LED** on the board silk. Cut the trace on this jumper to cut power to the " **on**" LED.
# Adafruit AS7331 UV / UVA / UVB / UVC Sensor
## CircuitPython & Python
It's easy to use the **AS7331** with Python or CircuitPython, and the [Adafruit\_CircuitPython\_AS7331](https://github.com/adafruit/Adafruit_CircuitPython_AS7331) module. This module allows you to easily write Python code that allows you to read the **AS7331** UV sensor. You can use this sensor with any CircuitPython microcontroller board or with a computer that has GPIO and Python [thanks to Adafruit\_Blinka, our CircuitPython-for-Python compatibility library](https://learn.adafruit.com/circuitpython-on-raspberrypi-linux).
## CircuitPython Microcontroller Wiring
First, wire up an AS7331 to your board exactly as shown below. Here's an example of wiring a Feather RP2040 to the AS7331 with I2C using one of the handy [**STEMMA QT**](https://learn.adafruit.com/introducing-adafruit-stemma-qt) connectors:
- **Board STEMMA 3V** to **breakout STEMMA **** VIN (red wire)**
- **Board STEMMA GND** to **breakout** **STEMMA** **GND (black wire)**
- **Board STEMMA SCL** to **breakout** **STEMMA** **SCL (yellow wire)**
- **Board STEMMA SDA** to **breakout** **STEMMA** **SDA (blue wire)**
You can also use standard **0.100" pitch** headers to wire it up on a breadboard:
- **Board 3V** to **breakout** **VIN (red wire)**
- **Board GND** to **breakout** **GND (black wire)**
- **Board SCL** to **breakout** **SCL (yellow wire)**
- **Board SDA** to **breakout** **SDA (blue wire)**
## Python Computer Wiring
Since there's _dozens_ of Linux computers/boards you can use, below shows wiring for Raspberry Pi. For other platforms, [please visit the guide for CircuitPython on Linux to see whether your platform is supported](https://learn.adafruit.com/circuitpython-on-raspberrypi-linux).
Here's the Raspberry Pi wired to the UV sensor using I2C and a [**STEMMA QT**](https://learn.adafruit.com/introducing-adafruit-stemma-qt) connector:
- **Pi 3V** to **breakout STEMMA** **VIN (red wire)**
- **Pi GND** to **breakout** **STEMMA** **GND (black wire)**
- **Pi SCL** to **breakout** **STEMMA** **SCL (yellow wire)**
- **Pi SDA** to **breakout** **STEMMA** **SDA (blue wire)**
Finally, here is an example of how to wire up a Raspberry Pi to the UV sensor using a solderless breadboard:
- **Pi 3V** to **breakout** **VIN (red wire)**
- **Pi GND** to **breakout** **GND (black wire)**
- **Pi SCL** to **breakout** **SCL (yellow wire)**
- **Pi SDA** to **breakout** **SDA (blue wire)**
## Python Installation of AS7331 Library
You'll need to install the **Adafruit\_Blinka** library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. [Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready](https://learn.adafruit.com/circuitpython-on-raspberrypi-linux)!
Once that's done, from your command line run the following command:
- `pip3 install adafruit-circuitpython-as7331`
If your default Python is version 3, you may need to run `pip` instead. Make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!
## CircuitPython Usage
To use with CircuitPython, you need to first install the AS7331 library and its dependencies into the **lib** folder on your **CIRCUITPY** drive. Then you need to update **code.py** with the example script.
Thankfully, we can do this in one go. In the example below, click the **Download Project Bundle** button below to download the necessary libraries and the **code.py** file in a zip file. Extract the contents of the zip file, and copy the **entire **** lib ** ** folder ** and the ** code.py ** file to your ** CIRCUITPY** drive.
Your **CIRCUITPY/lib** folder should contain the following folders and file:
- **adafruit\_bus\_device/**
- **adafruit\_register/**
- **adafruit\_as7331.mpy**
## Python Usage
Once you have the library `pip3` installed on your computer, copy or download the following example to your computer, and run the following, replacing **code.py** with whatever you named the file:
`python3 code.py`
## Example Code
**If running CircuitPython:** Once everything is saved to the **CIRCUITPY** drive, [connect to the serial console](https://learn.adafruit.com/welcome-to-circuitpython/kattni-connecting-to-the-serial-console) to see the data printed out!
**If running Python: ** The console output will appear wherever you are running Python.
https://github.com/adafruit/Adafruit_CircuitPython_AS7331/blob/main/examples/as7331_simpletest.py
In the example, the UV sensor is instantiated on I2C. Then, in the loop, the UVA, UVB, UVC and temperature readings are printed to the serial console.
# Adafruit AS7331 UV / UVA / UVB / UVC Sensor
## Python Docs
# Adafruit AS7331 UV / UVA / UVB / UVC Sensor
## Arduino
Using the AS7331 UV sensor with Arduino involves wiring up the sensor to your Arduino-compatible microcontroller, installing the [Adafruit\_AS7331](https://github.com/adafruit/Adafruit_AS7331) library and running the provided example code.
## Wiring
Wire as shown for a **5V** board like an Uno. If you are using a ** 3V** board, like an Adafruit Feather, wire the board's 3V pin to the AS7331 VIN.
Here is an Adafruit Metro wired up to the AS7331 using the STEMMA QT connector:
- **Board 5V** to **breakout STEMMA** **VIN (red wire)**
- **Board GND** to **breakout** **STEMMA** **GND (black wire)**
- **Board SCL** to **breakout** **STEMMA** **SCL (yellow wire)**
- **Board SDA** to **breakout** **STEMMA** **SDA (blue wire)**
Here is an Adafruit Metro wired up using a solderless breadboard:
- **Board 5V** to **breakout** **VIN (red wire)**
- **Board GND** to **breakout** **GND (black wire)**
- **Board SCL** to **breakout** **SCL (yellow wire)**
- **Board SDA** to **breakout** **SDA (blue wire)**
## Library Installation
You can install the **Adafruit AS7331** library for Arduino using the Library Manager in the Arduino IDE.
Click the **Manage Libraries ...** menu item, search for **Adafruit AS7331** , and select the **Adafruit AS7331** library:
If asked about dependencies, click " **Install all**".
If the "Dependencies" window does not come up, then you already have the dependencies installed.
Warning: If the dependencies are already installed, you must make sure you update them through the Arduino Library Manager before loading the example!
## Example Code
https://github.com/adafruit/Adafruit_AS7331/blob/main/examples/fulltest/fulltest.ino
Upload the sketch to your board and open up the Serial Monitor ( **Tools -\> Serial Monitor** ) at 115200 baud. You should see that the sketch has found your connected AS7331 sensor. The default settings are written to the sensor. Then, continuous readings start. You'll see the UVA, UVB, UVC and temperature readings printed to the Serial Monitor every second.
# Adafruit AS7331 UV / UVA / UVB / UVC Sensor
## Arduino Docs
# Adafruit AS7331 UV / UVA / UVB / UVC Sensor
## WipperSnapper
Warning: We cannot currently support UVA+UVB+UVC in WipperSnapper version 1, due to only supporting one of each data type.
We picked UVB for now, so **this sensor can only report UVB** in v1, but fear not as WipperSnapper version 2 is _almost ready!_
V2 will be released later this year enabling simultaneous UVA, UVB, and UVC reporting.
## What is WipperSnapper
WipperSnapper is a firmware designed to turn any WiFi-capable board into an Internet-of-Things device without programming a single line of code. WipperSnapper connects to [Adafruit IO](https://io.adafruit.com/), a web platform designed ([by Adafruit!](https://www.adafruit.com/about)) to _display_, _respond_, and _interact_ with your project's data.
Simply load the WipperSnapper firmware onto your board, add credentials, and plug it into power. Your board will automatically register itself with your Adafruit IO account.
From there, you can add _components_ to your board such as buttons, switches, potentiometers, sensors, and more! Components are _dynamically _added to hardware, so you can immediately start interacting, logging, and streaming the data your projects produce without writing code.
If you've never used WipperSnapper, click below to read through the quick start guide before continuing.
[Quickstart: Adafruit IO WipperSnapper](https://learn.adafruit.com/quickstart-adafruit-io-wippersnapper)
## Wiring
First, wire up a AS7331 to your board exactly as follows. Here is an example of the AS7331 wired to an [Adafruit ESP32 Feather V2](https://www.adafruit.com/product/5400) using I2C [with a STEMMA QT cable (no soldering required)](https://www.adafruit.com/product/4210), or on a prototyping breadboard using wires / jumper cables.
- **Board 3V** to **breakout** **VIN (red wire)**
- **Board GND** to **breakout** **GND (black wire)**
- **Board SCL** to **breakout** **SCL (yellow wire)**
- **Board SDA** to **breakout** **SDA (blue wire)**
## Usage
Connect your board to Adafruit IO Wippersnapper and **[navigate to the WipperSnapper board list](https://io.adafruit.com/wippersnapper).**
On this page, **select the WipperSnapper board you're using** to be brought to the board's interface page.
If you do not see your board listed here - you need [to connect your board to Adafruit IO](https://learn.adafruit.com/quickstart-adafruit-io-wippersnapper) first.
On the device page, quickly **check that you're running the latest version of the WipperSnapper firmware**.
The device tile on the left indicates the version number of the firmware running on the connected board.
- **If the firmware version is green with a checkmark -** continue with this guide.
- **If the firmware version is red with an exclamation mark "!" -** [update to the latest WipperSnapper firmware](https://learn.adafruit.com/quickstart-adafruit-io-wippersnapper) on your board before continuing.
You can always update the WiFi settings by following the Circular Arrows (🔄️) update icon.
Next, make sure the sensor is plugged into your board and click the ** I2C Scan ** button.
You should see the AS7331's default I2C address of `0x74` pop-up in the I2C scan list
### I don't see the sensor's I2C address listed!
First, double-check the connection and/or wiring between the sensor and the board.
Then, reset the board and let it re-connect to Adafruit IO WipperSnapper.
With the sensor detected in an I2C scan, you're ready to add the sensor to your board.
**Click the New Component button or the + button** to bring up the component picker.
Adafruit IO supports a large amount of components. To quickly find your sensor, type `AS7331` into the search bar, then select the **AS7331** component.
On the component configuration page, the AS7331's sensor address should be listed along with the sensor's settings.
The **Send Every** option is specific to each sensor's measurements. This option will tell the Feather how often it should read from the AS7331 sensor and send the data to Adafruit IO. Measurements can range from every second to every 24 hours.
For this example, set the **Send Every ** interval to every 30 seconds.
Your device interface should now show the sensor components you created. After the interval you configured elapses, WipperSnapper will automatically read values from the sensor(s) and send them to Adafruit IO.
To view the data that has been logged from the sensor, click on the graph next to the sensor name.
Here you can see the feed history and edit things about the feed such as the name, privacy, webhooks associated with the feed and more. If you want to learn more about how feeds work, [check out this page](https://learn.adafruit.com/all-the-internet-of-things-episode-four-adafruit-io/advanced-feeds).
Info: If you have a serial monitor handy then WipperSnapper devices output information over the usb-serial port, and this sensor prints out all the UVA/UVB/UVC readings if you wanted to check UVA or UVC locally.
# Adafruit AS7331 UV / UVA / UVB / UVC Sensor
## Downloads
## Files
- [AS7331 Datasheet](https://cdn-learn.adafruit.com/assets/assets/000/142/836/original/AS7331_DS001047_4-00.pdf?1772724111)
- [EagleCAD PCB files on GitHub](https://github.com/adafruit/Adafruit-AS7331-UV-UVA-UVB-UVC-Sensor-PCB)
- [Fritzing object in the Adafruit Fritzing Library](https://github.com/adafruit/Fritzing-Library/blob/master/parts/Adafruit%20AS7331%20UV%20UVA%20UVB%20UVC%20Sensor.fzpz)
## Schematic and Fab Print
## Primary Products
### Adafruit AS7331 UV / UVA / UVB / UVC Sensor Breakout
[Adafruit AS7331 UV / UVA / UVB / UVC Sensor Breakout](https://www.adafruit.com/product/6476)
The **Adafruit AS7331 UVA / UVB / UVC Sensor Breakout** is a perfect solution to UV sensing, no matter what 'type' you're sensing. Most UV sensors do just UVA, maybe ambient light too. But the AS7331 can read and differentiate between all the three bands. That...
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## Featured Products
### STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long
[STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long](https://www.adafruit.com/product/4399)
This 4-wire cable is 50mm / 1.9" long and fitted with JST SH female 4-pin connectors on both ends. Compared with the chunkier JST PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
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[STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long](https://www.adafruit.com/product/4210)
This 4-wire cable is a little over 100mm / 4" long and fitted with JST-SH female 4-pin connectors on both ends. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
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[STEMMA QT / Qwiic JST SH 4-pin Cable with Premium Female Sockets](https://www.adafruit.com/product/4397)
This 4-wire cable is a little over 150mm / 6" long and fitted with JST-SH female 4-pin connectors on one end and premium female headers on the other. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and...
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