Hardware Overview

AS7331 Spectral UV Sensor

The AS7331 spectral UV sensor from ams measures UV radiation over three channels (UVA, UVB, and UVC). Each channel is isolated from the other and has its own photodiode with a built-in filter to help with accuracy and interference from other channels.

The AS7331 has extensive configuration options to customize the sensor's responsiveness, sensitivity, clock speed, and conversion time, among other settings. These configuration options allow users to optimize the sensor for their application. For example, a high gain setting results in a more sensitive response from the sensor but a lower maximum detectable irradiance (in µW/cm²) whereas a low gain has much less sensitivity but a much higher maximum detectable irradiance. For detailed information on the conversion equations and how all the available settings affect performance, refer to section 7.4 of the datasheet Note, these configurations apply across all three channels. It has four operating modes: Command (CMD), Continuous (CONT), Synchronized Start (SYNS), and Synchronized Start/End (SYND). The list below outlines the operating modes' behaviors:

• CMD Mode - "One-shot" mode. Takes a single measurement and conversion controlled by the I²C interface.
• CONT Mode - Continous mode. Takes continuous measurements and conversions on set intervals.
• SYNS Mode - Synchronized start mode. A connected microcontroller starts measurements through an I/O pin connected to the SYN pin.
• SYND Mode - Synchronized start and stop mode. A connected microcontroller starts and stops measurements through an I/O pin connected to the SYN pin.

The sensor operates over I²C with a pin-configured I²C address supporting four separate addresses (the breakout board sets this to 0x74 by default). Refer to the datasheet for a complete overview of the AS7331.

Qwiic and PTH Pins

Both boards include a pair of Qwiic connectors for the I²C interface (SDA, SCL, 3.3V, and Ground) as well as a 0.1"-spaced plated through hole (PTH) header that includes power supply pins (3.3V and Ground) the I²C interface as well as the AS7331's SYNC and READY/INT pins.

Power

The AS7331 accepts a supply voltage between 2.7V and 3.6V. Power to these boards can be supplied either over one of the Qwiic connectors or through the 3.3V and GND PTH pins.

LEDs

These breakouts only have a red Power LED to indicate whenever the board is powered.

Jumpers

Never modified a jumper before?

Check out our Jumper Pads and PCB Traces tutorial for a quick introduction!

How to Work with Jumper Pads and PCB Traces

The boards have three solder jumpers labeled PWR, A0, and A1. The PWR jumper completes the power LED circuit. Open it to disable the Power LED to help reduce the current consumption. The A0 and A1 solder jumpers control the AS7331's I²C address. They default to tie both address pins to Ground to set the I²C address to 0x74. The table below outlines the jumper positions for the four available I²C addresses:

A1	A0	Address
GND	GND	0x74 (default)
GND	VDD	0x75
VDD	GND	0x76
VDD	VDD	0x77

Board Dimensions

The Standard version of the Spectral UV Sensor measures 1.00" x 1.00" (25.4mm x 25.4mm) and the Mini version measures 1.00" x 0.50" (25.4mm x 12.7mm). The Standard has four mounting holes and the Mini has two mounting holes. All of these fit a 4-40 screw.

Need more measurements?

For more information about the board's dimensions, users can download the Eagle files(Standard & Mini) for the board. These files can be opened in Eagle and additional measurements can be made with the dimensions tool.

Eagle - Free Download!

Eagle is a CAD program for electronics that is free to use for hobbyists and students. However, it does require an account registration to utilize the software.

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Dimensions Tool

This video from Autodesk demonstrates how to utilize the dimensions tool in Eagle, to include additional measurements: