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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.
Important: This sensor has a fixed I2C address, so if you need to use more than one on the same I2C bus, you will typically need an I2C multiplexer.
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
| Product | Adafruit TSL2591 High Dynamic Range Digital Light Sensor - STEMMA QT |
|---|---|
| Main Sensor | TSL2591 digital luminosity sensor |
| Light Channels | Infrared and full-spectrum photodiodes |
| Lux Range | 188 uLux sensitivity up to 88,000 Lux |
| Dynamic Range | Up to 600,000,000:1 |
| Interface | I2C |
| Voltage Range | 3.3V to 5V input via onboard regulator |
| Current Draw | About 0.4mA active, less than 5uA in power-down mode |
| Operating Temperature | -30°C to 80°C |
| I2C Address | Fixed address configuration; board/chip uses 7-bit addresses 0x29 and 0x28 as noted by Adafruit |
| Connectors | Dual STEMMA QT / Qwiic-compatible JST SH connectors |
| Dimensions | 19mm × 16mm × 1mm |
| Weight | 1.1g |
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
What makes this better than a photoresistor?
It provides digital measurements, supports gain and timing adjustments, and can calculate lux more accurately across a much wider light range.
Can it detect infrared light too?
Yes. The sensor includes both infrared and full-spectrum photodiodes.
Does it need an analog pin?
No. It communicates digitally over I2C.
Can I use more than one on the same I2C bus?
Not directly in most cases, because the address is fixed. An I2C multiplexer is the usual solution.
Is the STEMMA QT cable included?
No. The board has STEMMA QT connectors, but the cable is sold separately.
Manila stock. Order before 16:00 PHT, ships today via J&T or LBC. Provincial: 1–3 working days.
Schools / class POs: we accept Purchase Orders for accredited schools and universities. contact us with your PO details.
Returns: 7-day inspection window for DOA units. Email proof of issue and we ship a replacement.
Compatibility & downloads
// downloads
- GitHub PCB repo git
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