Mike Rankin's Compact Thermal Camera Packs a High-Performance Parallel Display in a Tiny Footprint

Maker Mike Rankin has designed a low-cost compact thermal camera that pairs a Melexis MLX90640 thermal sensor with an Espressif ESP32-S3 microcontroller on a tiny custom Arduino-compatible development board no larger than its own 1.69" color display.

"This project evolved from a customer project who needed a large 2.4" LCD," Rankin explains of the board design. "I was pretty sure that going with an ESP32-S3 bare chip would allow everything to fit on the backside of a 1.69" screen. Previous revisions used an SPI bus, but the refresh rate was far too slow. Changing the 1.69" screen [to] this eight-bit bus type improved the refresh dramatically."

That eight-bit parallel data bus, which connects the color display to the ESP32-S3 on its rear, comes at the cost of tying up significantly more general-purpose input/output (GPIO) pins than using the more typical SPI bus — "but," as Rankin points out, "the S3 has plenty left over." I2C, meanwhile, is used to talk to the Melexis MLX90640 on the board's obverse side — a far-infrared thermal sensor offering a 32×24 resolution for 768 individual measurement zones.

Elsewhere on the board is a connector for a lithium-polymer battery, monitored over the I2C bus, and four push buttons — two for user tasks, and one each for reset and boot. "When first plugged in the [serial] port will appear and disappear over and over," Rankin notes of one minor bug in the design. "Holding down the boot button (B) and tapping the reset (R) button once sorts this out."

"It's been years since I've sold projects," Rankin says, "but this is one of my favorites and something I've always wanted to purchase. The design files are all available if you would like to assemble your own or change the design yourself."

Those design files are available on GitHub under an unspecified license; assembled units, meanwhile, are available to order on Rankin's Tindie store for just $65 each.