DIY Thermal Camera with MLX90640

The MLX90640 is a 32x24 pixel thermal sensor array that interfaces over I2C. It's not cheap (~$50) but it enables a genuine thermal camera for a fraction of the cost of commercial units.

The I2C clock must be set to 1MHz (Fast Mode Plus) to achieve the full 32fps frame rate — at 400kHz you're limited to about 4fps. The sensor outputs calibrated temperature values after on-chip processing using factory calibration data stored in EEPROM. The Melexis C library handles the calibration math; porting it to a Raspberry Pi is straightforward.

Display: I ran the MLX90640 on a Pi Zero W with a 240x320 SPI TFT. Each 32x24 pixel thermal frame is bicubically upscaled to fill the display. A rainbow colormap makes warm objects obvious. Useful for: finding heat leaks in a house, checking if electronic components are running hot, detecting warm bodies, and finding hot spots in PCBs under load.