Adafruit MAX44009 Lux Light Sensor

Easily measure light levels with the MAX44009 lux sensor.

by Tim C

published April 15, 2026, last edited May 07, 2026

posted in Adafruit Products Sensors/ Light Arduino Compatibles CircuitPython STEMMA

Beginner

Product guide

Arduino

Using the MAX44009 breakout with Arduino involves wiring up the breakout to your Arduino-compatible microcontroller, installing the Adafruit_MAX44009 library, and running the provided example code.

Wiring

Wire as shown for a 5V board like an Uno. If you are using a 3V board, like an Adafruit Feather, wire the board's 3V pin to the sensor VIN.

Here is an Adafruit Metro wired up to the sensor using the STEMMA QT connector:

Wiring illustration showing Adafruit Metro wired to the MAX44009 breakout via STEMMA QT connector to pins 5V, GND, SCL, and SDA

Board 5V to breakout VIN (red wire)
Board GND to breakout GND (black wire)
Board SCL to breakout SCL (yellow wire)
Board SDA to breakout SDA (blue wire)

Here is an Adafruit Metro wired up using a solderless breadboard:

Wiring illustration showing Adafruit Metro connected to the MAX44009 breakout via solderless breadboard connected to pins 5V, GND, SCL, and SDA

Board 5V to breakout VIN (red wire)
Board GND to breakout GND (black wire)
Board SCL to breakout SCL (yellow wire)
Board SDA to breakout SDA (blue wire)

Library Installation

You can install the Adafruit MAX44009 library for Arduino using the Library Manager in the Arduino IDE.

Arduino IDE showing the tools menu open with Manage Libraries highlighted

Click the Manage Libraries ... menu item, search for Adafruit MAX44009, and select the Adafruit MAX44009 library:

Arduino IDE library manager open with "Adafruit MAX44009" in the search box and library in the results list.

If asked about dependencies, click "Install all".

Arduino IDE pop up window asking to install dependencies for the MAX44009 driver

If the "Dependencies" window does not come up, then you already have the dependencies installed.

If the dependencies are already installed, you must make sure you update them through the Arduino Library Manager before loading the example!

Example Code

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/*
 * Simple example for the MAX44009 Ambient Light Sensor
 *
 * Written by Limor 'ladyada' Fried with assistance from Claude Code for
 * Adafruit Industries. MIT license, check license.txt for more information
 *
 * Reads lux every 100ms in auto-ranging mode. Serial Plotter friendly.
 */

#include <Adafruit_MAX44009.h>

Adafruit_MAX44009 max44009;

void setup() {
  Serial.begin(115200);
  while (!Serial)
    delay(10);

  if (!max44009.begin()) {
    Serial.println(F("Could not find MAX44009 sensor!"));
    while (1)
      delay(10);
  }
}

void loop() {
  float lux = max44009.readLux();

  if (!isnan(lux)) {
    Serial.print(F("Lux: "));
    Serial.println(lux);
  }

  delay(100);
}

/*
 * Simple example for the MAX44009 Ambient Light Sensor
 *
 * Written by Limor 'ladyada' Fried with assistance from Claude Code for
 * Adafruit Industries. MIT license, check license.txt for more information
 *
 * Reads lux every 100ms in auto-ranging mode. Serial Plotter friendly.
 */

#include <Adafruit_MAX44009.h>

Adafruit_MAX44009 max44009;

void setup() {
  Serial.begin(115200);
  while (!Serial)
    delay(10);

  if (!max44009.begin()) {
    Serial.println(F("Could not find MAX44009 sensor!"));
    while (1)
      delay(10);
  }
}

void loop() {
  float lux = max44009.readLux();

  if (!isnan(lux)) {
    Serial.print(F("Lux: "));
    Serial.println(lux);
  }

  delay(100);
}

View on GitHub

Upload the sketch to your board and open up the Serial Monitor (Tools -> Serial Monitor) at 115200 baud. You'll see the MAX44009 recognized over I2C. Then, the reading values of different light channels will be printed out to the Serial Monitor.