Słomkowski's technical musings

Playing with software, hardware and touching the sky with a paraglider.

Cheap flight computer combining Kobo Mini and BlueFly Vario module


Using e-book reader Kobo Mini with BlueFly Vario is a really cheap alternative to of-the-shelf paragliding variometers. I have built one with custom 3D-printed case.

Vario- and altimeter is a must if you do free-flying, even in paramotoring it’s nice to have one. These devices are not cheap, so I decided to build one by following this tutorial.

My device has to meet following requirements:

Apart from combining XCSoar, Kobo Mini and Blue Fly Vario, I designed in FreeCad a custom 3D-printed case for the module, so everything sits together nice and tight. The project repository is on GitHub. The case has holes, so the beeps are clearly audible even when I wear noise-muffling headset. Despite this, I added mini jack socket for the headset. Speaker’s volume is adjustable programmatically. To the back of the Kobo I glued stripes of velcro tape, so I can easily attach it to the reserve compartment as shown in the photo:

The module’s pressure sensor is secured with a piece of foam as described in the manual. The case has holes for the speaker; they are covered with a piece of dark cloth. There is also a piece of rope attached to the case which prevents the device from falling down in an unlikely scenario of velcro failure.

The case is attached to Kobo by two M3 (3 mm) screws with nuts. First you have to put the case on the Kobo and mark the holes’ positions. The holes are positioned in such way that they don’t collide with electronics but be careful when drilling anyway. I also made a hole for RESET button on the Kobo’s back, because XCSoar had hanged up several times.

Replacing broken Kobo Mini e-ink display

After a couple of months an e-ink display in my Kobo got broken because of impact; black stripes littered half of the screen. I decided to replace it. First, I opened Kobo up to make sure I would order an appropriate model.

Remove the cover and unplug the battery connector then unplug the display. Unscrew four screws holding the PCB. Move the board aside:

Unscrew four screws joining magnesium frame to the plastic bezel. Remove the frame with the display attached. The display is glued to the frame by two stripes of double-sided tape. Use kitchen knife to gently separate them, as shown in the photos.

The original display had following markings on it:

ED050SC3(LF) H1 EMN50A5011(B144)
E1N004E41K5V03797AT

The exact type is ED050SC3. I bought mine on AliExpress for $15. The new display is protected by the transparent adhesive tape; remember to remove it before the reassembly.