Overview

The TSL2591 (TSL25911FN) is an ultra-high dynamic range digital ambient light sensor (ALS) manufactured by ams OSRAM (formerly TAOS). Built as the advanced successor to the popular TSL2561, it features a massive 600,000,000:1600,000,000 : 1 dynamic range, measuring light levels from sub-lux starlight/moonlight (188 μLux188\ \mu\text{Lux} minimum detectable signal) up to full bright sunlight (88,000 Lux).

The TSL2591 incorporates dual integrating photodiodes:

  • Channel 0 (CH0): Full-spectrum diode (detects both Visible and Infrared light).
  • Channel 1 (CH1): Infrared diode (detects Infrared light only).

By calculating the difference between channels in software, the sensor accurately models the human eye photopic response curve while allowing independent IR spectrum intensity measurement over I2CI^2C (0x29).

Quick reference

Operating voltage (VCC)3.3 V to 5.0 V DC (breakout module includes 3.3V LDO regulator)
IC supply voltage (VDD)2.7 V to 3.6 V DC (3.3 V nominal)
InterfaceI2CI^2C (Fast Mode up to 400 kHz)
Fixed I2CI^2C address0x29
Dynamic range600,000,000 : 1
Lux range188 μLux188\ \mu\text{Lux} (0.000188 Lux0.000188\text{ Lux}) to 88,000 Lux
Resolution16-bit dual-channel digital count outputs (0 to 65,535 counts)
Programmable GainLow (×1\times 1), Med (×25\times 25), High (×428\times 428), Max (×9876\times 9876)
Programmable Integration Time100 ms, 200 ms, 300 ms, 400 ms, 500 ms, 600 ms

Pinout

STEMMA QT / Qwiic 4-pin connector & 0.1" header pins:

PinNameTypeDescription
1VIN / VCCPowerSupply input (+3.3 V to +5.0 V DC)
2GNDPowerGround reference (0 V)
3SCLDigital InputI2CI^2C Serial Clock
4SDADigital Input / OutputI2CI^2C Serial Data
5INTDigital OutputActive-Low interrupt output (programmable lux thresholds)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply Voltage (Module)VCCV_{CC}3.33.3 / 5.05.5VPower rail with LDO
Active Supply CurrentIDDI_{DD}—250350µAActive integration state
Shutdown CurrentIsdI_{sd}—3.05.0µASoftware shutdown mode
Min Detectable LuxLuxminLux_{min}—0.000188—LuxMax Gain (×9876\times 9876), tint=600 mst_{int} = 600\text{ ms}
Max Detectable LuxLuxmaxLux_{max}—88000—LuxLow Gain (×1\times 1), tint=100 mst_{int} = 100\text{ ms}
Peak Sensitivity Wavelengthλp\lambda_p—630 (CH0) / 850 (CH1)—nmVisible and IR peaks

Gain Settings & Integration Time Table

Gain SettingMultiplier SymbolTypical Application
TSL2591_GAIN_LOW×1\times 1Bright direct sunlight (up to 88,000 Lux)
TSL2591_GAIN_MED×25\times 25Standard indoor room lighting
TSL2591_GAIN_HIGH×428\times 428Dim indoor lighting / overcast shade
TSL2591_GAIN_MAX×9876\times 9876Extremely dark environments / moonlight / starlight

Lux Calculation Math

Lux=(CH0−CH1Gain×Integration Time (s))×CLUX_DF\text{Lux} = \left( \frac{CH0 - CH1}{\text{Gain} \times \text{Integration Time (s)}} \right) \times C_{LUX\_DF}

Where CLUX_DF=408.0C_{LUX\_DF} = 408.0 (Lux Device Factor constant for TSL2591).

Wiring

TSL2591 Pin→Arduino / MCUESP32Notes
VIN5V / 3.3V3.3VModule includes 3.3V LDO
GNDGNDGNDSystem ground
SCLA5GPIO 22I2CI^2C Clock
SDAA4GPIO 21I2CI^2C Data

Example (Adafruit_TSL2591 Library)

cpp
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include "Adafruit_TSL2591.h"

Adafruit_TSL2591 tsl = Adafruit_TSL2591(2591); // Pass sensor ID

void setup() {
  Serial.begin(9600);
  Serial.println("Adafruit TSL2591 Light Sensor Test");

  if (!tsl.begin()) {
    Serial.println("TSL2591 not found! Check wiring.");
    while (1);
  }
  
  // Configure gain and integration time
  tsl.setGain(TSL2591_GAIN_MED);      // 25x gain
  tsl.setTiming(TSL2591_INTEGRATIONTIME_100MS); // 100 ms integration
}

void loop() {
  // Read combined 32-bit channel data (CH0 and CH1)
  uint32_t lum = tsl.getFullLuminosity();
  uint16_t ir = lum >> 16;
  uint16_t full = lum & 0xFFFF;
  uint16_t visible = full - ir;

  float lux = tsl.calculateLux(full, ir);

  Serial.print("IR: "); Serial.print(ir);
  Serial.print(" | Full Spectrum: "); Serial.print(full);
  Serial.print(" | Visible: "); Serial.print(visible);
  Serial.print(" | Calculated Lux: "); Serial.println(lux);

  delay(1000);
}

Common mistakes

  • I2C Address Collision: TSL2591 has a fixed hardcoded I2CI^2C address (0x29).
  • Saturation in direct sunlight: Operating at Medium or High gain under full sunlight causes 16-bit register saturation (65,535 count cap). When full-spectrum readings hit 65,535, lower the gain setting to TSL2591_GAIN_LOW (×1\times 1).

Notes

  • TSL2591 vs TSL2561: TSL2591 offers 600,000,000:1600,000,000 : 1 dynamic range (vs 1,000,000:11,000,000 : 1 for TSL2561), higher max Lux (88,00088,000 vs 40,00040,000), and improved sub-lux sensitivity.

Assets & downloads