Adafruit LTR390 UV Light Sensor - STEMMA QT / Qwiic

Overview

Adafruit LTR390 UV Light Sensor - STEMMA QT / Qwiic is a digital UV and ambient light sensing breakout built around the LTR390. It is designed for projects that need real UVA measurement, with a peak spectral response between 300 and 350nm, plus visible ambient light sensing on the same board.

Unlike sensors that estimate UV exposure indirectly from light levels, the LTR390 senses the UV spectrum itself. This sensor does not output UV Index directly; instead, it provides true UV sensing data that you can use in your own application logic, logging, or sun-exposure experiments.

The breakout uses a simple I2C interface and comes in Adafruit's STEMMA QT form factor, making it easy to connect to Arduino, Raspberry Pi, Feather, and other compatible development boards. Since the biasing and ADC are handled internally, you do not need an external ADC to start reading the sensor.

Features

• LTR390 digital sensor for UVA and ambient light measurement
• Peak UV spectral response between 300 and 350nm
• Measures true UV spectrum light rather than UV Index approximations based on light level
• Simple I2C interface for microcontrollers and microcomputers
• STEMMA QT / SparkFun Qwiic compatible connectors for fast wiring
• Works with breadboards for prototyping
• Compatible with 3.3V logic and 5V voltage levels
• Internal biasing and ADC, so no external ADC is required

Applications

Ideal for environmental sensing, weather and outdoor data logging, wearable exposure studies, and projects that monitor sun exposure before deciding when to cover up.

Specifications

Important Notes

QT cable is not included.

The LTR390 does not provide UV Index readings directly. If your project specifically needs UV Index output, use your own conversion method or choose a sensor intended for that purpose.