Aircraft Engine Preheater Remote Switch (v2.0)

My bespoke Remote Controlled Engine Preheader (v1.0) worked pretty well overall. I had a few instances where the controller went offline, but after a few software revisions, it proved to be quite stable. However, it certainly left plenty of room for improvements with it's primitive seven-segment display and three LED lights... plus, frankly, it looked like a bomb. All of that is fixed in 2.0!

Changes for v2.0

  • Added a SHT31-D temperature and humidity sensor
  • A 20x4 LCD character display replaces the primitive 7-segment display
  • A Raspberry Pi Nano replaces the old 1B (MUCH faster and smaller)
  • Added manual input buttons on the device: turn it ON/OFF, shutdown the device, etc.
  • Added a proper housing.
  • Performed software updates (and in 2/3 cases, major overhauls) on all three fronts: controller, server/API, and mobile web app

Deferred for a future release:

  • Graphic LED display
  • Camera


The Hardware

The goal of the hardware, aside from introducing several more components, was to make it look clean and significantly more polished than 1.0.

More-polished? Not yet. Prototype 1's breadboard rats' nest. Note that I used a Raspberry Pi 2B for prototyping, which is functionally-identical to the Nano.

Prototype 1, sporting a very classy panel made from a USPS box.

Assembling the "production" PCB. I stopped short of etching a PCB. Most of the wiring will be hidden by the Raspberry Pi that sits on top.

The guts of the device in the housing, mostly assembled. The climate sensor (top left on the PCB) was originally mounted to the PCB as shown in this photo, but that turned out to be a bad idea in practice, yielding inaccurate data. It was relocated to the back plate with a hole exposing the sensor to outside air during a hangar field repair.