How to Use MLX90640 Adafruit Thermal Sensor: Examples, Pinouts, and Specs

The MLX90640 Adafruit Thermal Sensor is a high-resolution infrared (IR) thermal camera module designed for non-contact temperature measurement and thermal imaging. Manufactured by Adafruit, this sensor features a 32x24 pixel IR sensor array, enabling it to detect temperature variations across a wide field of view. It is compact, versatile, and ideal for applications requiring precise thermal data.

• Robotics: Thermal mapping and obstacle detection.
• HVAC Systems: Monitoring temperature distribution and efficiency.
• Smart Home Systems: Detecting human presence or heat sources.
• Industrial Automation: Equipment monitoring and fault detection.
• Medical Devices: Non-contact temperature measurement.
• Research and Development: Thermal analysis and prototyping.

The following table outlines the key technical details of the MLX90640 Adafruit Thermal Sensor:

The MLX90640 module has the following pinout:

1. Power the Sensor: Connect the VIN pin to a 3.3V or 5V power source and the GND pin to ground.
2. I2C Communication: Connect the SDA and SCL pins to the corresponding I2C pins on your microcontroller (e.g., Arduino UNO).
3. Pull-Up Resistors: Ensure that the I2C lines have appropriate pull-up resistors (typically 4.7kΩ).
4. Install Libraries: Use the Adafruit MLX90640 library for easy integration with Arduino or other platforms.
5. Read Data: Use the library functions to read temperature data and process the thermal image.

• Power Supply: Ensure a stable power supply to avoid noise in the thermal readings.
• I2C Address: The default I2C address is 0x33. If using multiple sensors, ensure address conflicts are resolved.
• Refresh Rate: Higher refresh rates may increase power consumption.
• Ambient Conditions: Avoid direct sunlight or reflective surfaces, as they can affect accuracy.
• Calibration: The sensor is factory-calibrated, but additional calibration may be required for specific applications.

Below is an example of how to use the MLX90640 with an Arduino UNO:

#include <Wire.h>
#include <Adafruit_MLX90640.h>

// Create an instance of the MLX90640 object
Adafruit_MLX90640 mlx;

// Define the frame buffer to store temperature data
float frame[32 * 24]; // 32x24 resolution

void setup() {
  Serial.begin(115200);
  while (!Serial); // Wait for Serial Monitor to open

  Serial.println("Initializing MLX90640...");

  // Initialize the MLX90640 sensor
  if (!mlx.begin(0x33)) { // Default I2C address is 0x33
    Serial.println("Failed to find MLX90640 sensor. Check wiring!");
    while (1);
  }

  // Set the refresh rate to 8Hz
  mlx.setMode(MLX90640_INTERLEAVED);
  mlx.setRefreshRate(MLX90640_8_HZ);

  Serial.println("MLX90640 initialized successfully!");
}

void loop() {
  // Read thermal data into the frame buffer
  if (mlx.getFrame(frame) != 0) {
    Serial.println("Failed to read frame data!");
    return;
  }

  // Print the temperature data
  for (int i = 0; i < 32 * 24; i++) {
    Serial.print(frame[i], 2); // Print temperature with 2 decimal places
    Serial.print(" ");
    if ((i + 1) % 32 == 0) { // Newline after every 32 pixels
      Serial.println();
    }
  }

  delay(125); // Delay to match the refresh rate (8Hz = 125ms)
}

1. Sensor Not Detected

   • Cause: Incorrect wiring or I2C address mismatch.
   • Solution: Verify the connections and ensure the I2C address matches the one in the code.

2. Inaccurate Temperature Readings

   • Cause: Reflective surfaces or environmental interference.
   • Solution: Avoid reflective surfaces and ensure the sensor is not exposed to direct sunlight.

3. Data Read Errors

   • Cause: I2C communication issues.
   • Solution: Check pull-up resistors on the I2C lines and ensure proper clock speed (typically 100kHz or 400kHz).

4. Slow Refresh Rate

   • Cause: Default refresh rate is too low.
   • Solution: Increase the refresh rate using the setRefreshRate() function, but note the trade-off with power consumption.

• Can the MLX90640 detect humans? Yes, the sensor can detect humans based on their thermal signature.

• What is the maximum distance for accurate readings? The effective range depends on the field of view and target size, but it is typically a few meters.

• Can I use multiple MLX90640 sensors on the same I2C bus? Yes, but you must configure each sensor with a unique I2C address.

• Is the sensor waterproof? No, the MLX90640 is not waterproof and should be protected from moisture.

• Does the sensor require calibration? The sensor is factory-calibrated, but additional calibration may improve accuracy for specific applications.