Mark Kiehl Gives a Light Aircraft an ePaper Upgrade with a Glare-Free Temperature Monitor

Engineer Mark Kiehl has created an ePaper display for a light aircraft, designed to monitor up to six K-type temperature probes and output the results to a daylight-readable display — and it's based around a custom FeatherWing board.

"[The project's] functional requirements [were]: read up to 6× K type thermocouples," Kiehl notes of the project; display temperature readings and indicate visually if any are lower or higher than normal; daylight readable display; 12 VDC power input."

The idea for the project, brought to our attention by Adafruit, was to build a low-cost at-a-glance measure of temperature at various parts of the aircraft's engine, without distracting lights or with a display that would be washed out when flying above the clouds. The Adafruit Feather M0 Basic Proto microcontroller board, with its Microchip ATSAMD21, was chosen to drive everything, along with a FeatherWing 2.9" ePaper display — with the choice of single- or tri-color.

Rather than connecting the two together directly, though, Kiehl designed a custom FeatherWing which mounts behind the display and hosts both the microcontroller board and suitable amplifiers for up to six K-type thermocouple temperature probes. "Analog input connections A0 to A5 are routed to each of the thermocouple amplifiers," Keihl explains, "but each one has a pair of tabs with a thin trace that can be cut if the analog input assignments need to be changed. The seventh optional thermocouple breakout connection is not used for this application."

The finished display sits in a custom cut-out in the control panel of a Skystar Kitfox Classic IV fixed-wing single-engine two-seater aircraft, next to the traditional analog dials. As it's not lit, it's not much use at night without cockpit lighting — but the electrophoretic display means it's highly readable in sunlight, even when shining directly onto the display.

The full project write-up, with source code, is available on Keihl's website.