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 rat's 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 rats' nest will be hidden by the Raspberry Pi that sits on top.

The guts of the device in the housing, mostly assembled. Note: the climate sensor 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. In a later field repair, it was relocated to the back plate with a hole exposing the sensor to outside air. The wiring will be cleaned-up later by adding a plug, socket, and dongle like the other components have.