How to Use Ambient Light Sensor: Examples, Pinouts, and Specs

The CQRobot TSL25911FN Ambient Light Sensor is a highly sensitive device designed to measure the intensity of light in the surrounding environment and convert it into an electrical signal. This sensor is ideal for applications requiring precise light measurements, such as in smartphones, tablets, and other portable devices, as well as in industrial and environmental monitoring systems.

1. Power Supply: Connect the VDD pin to a 3.3V power supply and the GND pin to the ground.
2. I2C Communication: Connect the SDA pin to the SDA line of your microcontroller and the SCL pin to the SCL line.
3. I2C Address Selection: Connect the ADDR pin to GND for the default I2C address (0x29) or to VDD for an alternate address (0x28).
4. Interrupt Pin: Optionally, connect the INT pin to a digital input on your microcontroller to handle interrupts.

• Power Supply: Ensure the power supply voltage is within the specified range (2.7V to 3.6V) to avoid damaging the sensor.
• I2C Pull-up Resistors: Use appropriate pull-up resistors (typically 4.7kΩ) on the SDA and SCL lines to ensure proper I2C communication.
• Ambient Light: Place the sensor in a location where it can accurately measure the ambient light without obstructions.

#include <Wire.h>

// TSL25911FN I2C address
#define TSL25911FN_ADDR 0x29

void setup() {
  Serial.begin(9600);
  Wire.begin(); // Initialize I2C communication

  // Initialize the TSL25911FN sensor
  Wire.beginTransmission(TSL25911FN_ADDR);
  Wire.write(0x00); // Command register
  Wire.write(0x03); // Power on the sensor
  Wire.endTransmission();
}

void loop() {
  uint16_t ch0, ch1;

  // Read channel 0 (visible + IR)
  Wire.beginTransmission(TSL25911FN_ADDR);
  Wire.write(0x14); // Data register for channel 0
  Wire.endTransmission();
  Wire.requestFrom(TSL25911FN_ADDR, 2);
  ch0 = Wire.read();
  ch0 |= (Wire.read() << 8);

  // Read channel 1 (IR only)
  Wire.beginTransmission(TSL25911FN_ADDR);
  Wire.write(0x16); // Data register for channel 1
  Wire.endTransmission();
  Wire.requestFrom(TSL25911FN_ADDR, 2);
  ch1 = Wire.read();
  ch1 |= (Wire.read() << 8);

  // Calculate lux (simplified formula)
  float lux = (ch0 - ch1) * (1.0 / 0.39);

  Serial.print("Lux: ");
  Serial.println(lux);

  delay(1000); // Wait for 1 second before next reading
}

1. No I2C Communication: Ensure the SDA and SCL lines are correctly connected and that pull-up resistors are used.
2. Incorrect Lux Readings: Verify that the sensor is not obstructed and is placed in an appropriate location for accurate light measurement.
3. Sensor Not Powering On: Check the power supply voltage and connections to the VDD and GND pins.

• Check Connections: Double-check all wiring and connections to ensure they are secure and correct.
• Use a Multimeter: Measure the voltage at the VDD pin to ensure it is within the specified range.
• Verify I2C Address: Ensure the correct I2C address is used in the code, based on the ADDR pin connection.

By following this documentation, users can effectively integrate and utilize the CQRobot TSL25911FN Ambient Light Sensor in their projects, ensuring accurate and reliable light measurements.