Measure Tiny Glows and Bright Sunlight with One Digital Light Sensor

The Adafruit TSL2591 High Dynamic Range Digital Light Sensor - STEMMA QT is a powerful luminosity sensor for projects that need accurate light readings across a very wide range of conditions. From extremely dim environments to bright daylight, this breakout is designed to give you cleaner, more flexible measurements than a simple photoresistor.

At the heart of the board is the TSL2591, an advanced digital light sensor that includes both infrared and full-spectrum photodiodes. That means you can measure light more intelligently and calculate lux more accurately, instead of relying on a basic sensor that sees only part of the picture.

Why you'll love it

• Huge measurement range: Detects from ultra-low light up to bright outdoor conditions
• Better than a simple photocell: Digital readings with gain and integration control for more precise lux calculations
• IR and full-spectrum sensing: Helps distinguish light more effectively than single-channel sensors
• Low power operation: Great for battery-powered or data-logging builds
• No analog pin required: Built-in ADC means you can use it with digital-only microcontrollers over I2C
• STEMMA QT ready: Easy plug-and-play wiring for fast prototyping

What you can build

This breakout is ideal for automatic brightness control, indoor and outdoor light monitoring, smart lamps, solar or daylight studies, environmental logging, wearable light sensing, and projects that need to react differently in low-light and high-light environments.

Starter bundles

Pair it with an Arduino-compatible board, Raspberry Pi, or Adafruit Feather, plus a STEMMA QT cable for a quick no-solder light sensing setup.

Recommended add-ons

Useful add-ons include OLED displays, microSD logging boards, battery packs, QT cables, and an I2C multiplexer if you want to connect multiple same-address sensors.

Technical specifications

Pinout & usage notes

This sensor communicates over I2C, so wiring is simple and it works well with modern microcontrollers and single-board computers. Since the ADC is built in, you do not need an analog input pin to use it.

The TSL2591 is especially useful when a project has to work across dramatically changing lighting conditions. You can adjust gain and integration timing in software to better handle very dim scenes or brighter environments.

What’s in the box

1 × Adafruit TSL2591 High Dynamic Range Digital Light Sensor breakout

Note: STEMMA QT cable is not included.

Frequently Asked Questions