The Adafruit LTR-303 is a low-cost I2C digital light sensor that provides 16-bit measurements for both infrared and visible+IR spectrums. Subtract one from the other to get human-visible light readings. With configurable gain and integration time, it can measure from 0 to over 65,000 lux — suitable for everything from dim indoor lighting to bright sunlight.

Unlike the simpler LTR-329, the LTR-303 includes alert and interrupt capabilities, allowing you to trigger a pin when light levels go above or below configurable thresholds — ideal for ultra-low-power applications. This STEMMA QT breakout includes voltage regulation and level shifting for both 3.3 V and 5 V systems.

Key Features

• Dual-Spectrum Sensing – 16-bit measurements for both infrared and visible+IR light
• Wide Lux Range – 0 to 65,000+ lux with configurable gain and integration time
• Alert / Interrupt Output – Trigger pin when readings exceed configurable high/low thresholds
• I2C Interface – Simple two-wire communication
• STEMMA QT / Qwiic – Solderless I2C connectors for easy plug-and-play wiring
• 3.3 V and 5 V Compatible – Onboard voltage regulator and level shifting
• Arduino & CircuitPython Libraries – Ready-to-use drivers with example code

Ideal For

• Automatic display brightness adjustment
• Day/night detection and light-based automation
• Light-following robots and solar trackers
• Environmental monitoring and data logging

Package Contents

• 1× Adafruit LTR-303 Light Sensor Breakout (STEMMA QT)

Resources

• LTR-303 Arduino Library (GitHub)
• LTR-303 CircuitPython Library (GitHub)
• What is STEMMA QT?