Optical Thermal Scanning: MLX90614

Standard temperature sensors (like thermistors or the DHT22) require physical contact with the air or water. The Infrared (IR) Temperature Scanner project uses the MLX90614 module, which features a true optical lens, to measure the heat emanating from an object from a distance—the exact technology used in medical forehead thermometers.

The Emissivity Mathematics

The MLX90614 is an incredibly powerful I2C device. It doesn't just return a raw voltage; it calculates the complex thermal geometry internally.

1. Dual Sensors: Inside the tiny metal can are two separate IR chips. One reads the Ambient temperature of the room. The second points out the lens to read the Object's temperature.
2. The I2C Request: The Arduino uses the <Adafruit_MLX90614.h> library. You type mlx.readObjectTempC().
3. The chip instantly subtracts the ambient room noise from the thermal radiation hitting the lens, and transmits the exact parsed decimal back over the SDA/SCL lines.

The Laser Pointer Sighting

The sensor reads a "Cone" of radiation that gets wider the further away you are.

• To ensure accuracy, the user must know exactly what the center of the cone is looking at.
• You wire a KY-008 Laser Diode Module to a digital pin.
• When the user pulls the trigger (a push button), the laser turns on, placing a highly visible red dot precisely where the invisible IR sensor is taking its temperature reading!

Critical Components

• Arduino Uno/Nano: The processor.
• MLX90614 Infrared Thermometer Sensor (I2C breakout board).
• Small Laser Diode (5V).
• OLED Screen (128x64): To display huge, readable numbers.
• A 3D-Printed Pistol-Grip Enclosure to house the battery and sensor.