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

The Adafruit MLX90640 Thermal Camera is a sophisticated infrared thermal imaging module that offers a 32x24 array of temperature readings, translating to 768 individual temperature measurements. This module is capable of detecting temperatures ranging from -40°C to 300°C, making it suitable for a wide array of applications including human presence detection, HVAC control, medical imaging, and more. Its I2C interface facilitates easy integration with microcontrollers such as the Arduino UNO.

• Sensor Array: 32x24 IR sensor
• Measurement Range: -40°C to 300°C
• Interface: I2C
• Field of View (FoV): 55° x 35° (typical)
• Refresh Rate: 0.5Hz to 64Hz
• Supply Voltage: 3.3V to 5V
• Current Consumption: 23mA (typical)
• Operating Temperature: -40°C to 85°C

1. Power Supply: Connect the VDD pin to a 3.3V or 5V power supply from your microcontroller board.
2. Data Line: Connect the SDA pin to the I2C data line (SDA) on your microcontroller.
3. Clock Line: Connect the SCL pin to the I2C clock line (SCL) on your microcontroller.
4. Ground: Connect the GND pin to the ground on your microcontroller.

• Ensure that the power supply is stable and within the specified voltage range.
• Use pull-up resistors on the I2C data and clock lines if they are not already present on your microcontroller board.
• Avoid exposing the sensor to direct sunlight or high reflective surfaces to prevent inaccurate readings.
• For accurate temperature measurements, calibrate the sensor according to the manufacturer's guidelines.

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

Adafruit_MLX90640 mlx;

void setup() {
  Serial.begin(9600);
  while (!Serial); // Wait for Serial to be ready
  Serial.println("MLX90640 test");

  if (!mlx.begin()) {
    Serial.println("Failed to initialize MLX90640!");
    while (1);
  }
  Serial.println("MLX90640 initialized successfully");
}

void loop() {
  float mlx90640Frame[32 * 24]; // Buffer to store temperature readings

  // Capture the frame at the lowest resolution to increase the frame rate
  mlx.setMode(MLX90640_INTERLEAVED);

  // Request a frame capture
  if (mlx.getFrame(mlx90640Frame) == 0) {
    for (int i = 0; i < 24; i++) {
      for (int j = 0; j < 32; j++) {
        float temp = mlx90640Frame[i * 32 + j];
        Serial.print(temp);
        Serial.print(",");
      }
      Serial.println();
    }
  } else {
    Serial.println("Failed to read frame");
  }
  delay(1000); // Wait for 1 second before capturing next frame
}

• No Data on Serial Monitor: Ensure that the SDA and SCL connections are secure and that the correct I2C address is being used.
• Inaccurate Temperature Readings: Check for any sources of heat or reflection that could be affecting the sensor. Calibrate the sensor if necessary.
• Sensor Not Initializing: Make sure the power supply is within the specified range and that the sensor is not exposed to extreme temperatures.

• I2C Communication Issues: Use a logic analyzer to check the integrity of the I2C signals. Ensure pull-up resistors are correctly sized.
• Calibration: Follow the calibration procedure outlined in the sensor's datasheet to adjust for emissivity and ambient temperature.
• Updating Firmware: Keep the sensor's firmware updated to the latest version to ensure optimal performance.

Q: Can the MLX90640 be used to measure human body temperature? A: Yes, the MLX90640 can be used for human temperature detection, but it requires proper calibration and possibly additional optics for accurate measurements.

Q: What is the maximum distance at which the MLX90640 can accurately measure temperature? A: The maximum distance depends on the object size and the sensor's field of view. For small objects, the sensor should be closer to ensure accuracy.

Q: How can I increase the frame rate of the thermal camera? A: You can increase the frame rate by reducing the resolution or changing the refresh rate settings in the library, but this may affect the temperature accuracy and range.