Gliding Computer

Project details

1) Introduction

This winter, I was looking for an opportunity to build a little navigation computer into the instrument panel of my glider which can run the open source software XCSoar. This software has a mooving map and can display all relevant information needed in crosscountry or contest flights.

There are already some few gliding computers on market, but they are very expensive (1500€ to 5000€) and have their own software. Of course there are some mobile phones and tablets which can run XCSoar but the displays are not build for direct sunlight and you can´t integrate these devices into your instrument panel.

So I twiddeled with the idea to build my own gliding computer with some special features like a biofeedback system for the open source community.

Your Colibri T20 module with the industrial temperature range (-40°C to 85°C) is forming the best initial position for my project!

2) Technical specifications

Display: 7 inch

Power consumption: about 5W

Interfaces: 3 x Serial RS232, 4 x USB, WLAN

Frame: milled aluminium, black anodized

3) The major development steps

3.1) Find a suitable display

The display must be sunlight readable and should have less power consumption, because a glider has only one or two batteries with 7-12Ah at 12V for the whole avionics.

In general, there are three different display technologies to achieve good readability at bright illumination:

• Transmissive LCD: That´s a normal display, which needs hight bright LEDs to get full sunlight readability.
  
• Transflective LCD: It reflects (use sunlight) and transmits light (from LEDs), so you only need fiew power for the LEDs.
  
• E Ink: Those displays are used in ebook readers and they have fiewest consumption of electricity and the best sunlight readability. Of course there are some disadvantages like a slow reaction time and it´s very difficult to get a sample display for such a project.
  

At the long research I found a 7" display form PixelQi. This is a tranflective LCD and has a LVDS interface, which is suppurted by the Toradex Iris carrier board. In addtion, it was easy to get this display in Germany for an appropriate price.

3.2) Connect the display to the Iris Carrierboard

For embedded displays, there is no standard comming out on top for display connectors and pin assignments like on TV screens the HDMI interface. So nearly every company uses different connectors, which meant to build my own adapter board.

PixelQi uses a Flexible Flat Cable (FFC) with 0.5mm pitch, which exacerbates the manual soldering. But after watching some tutorials on the internet, it was possible to solder it by hand with a small soldering rod and a loupe to check the right position of the connector.

3.3) Build an extension board for RJ45 sockets, USB hub and Audio Jack

3.4) Build a case for the display and Iris Carrierboard

The case consists of two parts:

• The front side is a CNC milled aluminium frame, which enables a precise fitting of the LCD screen and allows to mount the gliding computer into the instrument panel. Certainly it has the aim to make it look professional.
• The back side is a 1mm thick bent aluminium sheet, which has some cutouts for the interfaces. Furthermore the Iris board and the interface board is screwed to this back side.
  

  SteFly V1 and SteFly V2:

  SteFly V2 is with 38mm as slim as the LX9000

3.5) Build a carbon fibre remote stick

After some drawings I sawed, shaped and sanded a positive core of the grip stick to the correct shape and painted it, so that it has a perfect glossy surface. Then I built a two-parts negative mold to be able to laminate the remote stick in one piece and to eject the completed carbon fibre stick.

For the input of the keystrokes I´m using five big push buttons and one joystick (4 directions + push button) to controle XCSoar. The keys are attached on a PCB and are routed to a little Arduino board which emulates a normal USB keyboard. The advantage of this is, that you only have to route one USB cable (4 leads) from the remote stick to your computer.

3.6) Build the biofeedback system (not finished yet)

Gliding flights can last many hours, where the pilot has to concentrate more or less depending on the height and weather conditions. So gliding is also a sport of endurance at which you should check the human body in relation to heart frequency and physical tension. To measur the physical tension of the glider pilot, you could place one force meter (DMS) on each rudder padel cable analyzed by the Colibri T20. Many glider pilots are pushing both legs to the rudder pedal, when they are stressed. This extra force to both rudder pedals should be recognized by the computer and displayed on the screen or output some sound.

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