An electronics, automobile, and DIY enthusiast has turned an old smartwatch into an interactive gear shift display in his 2001 Audi A4 (B5) luxury compact executive car. The project started as just a bit of digital bling for the gear stick, but inspired by fellow Redditor comments, Desmontei vibe coded a WearOS app to add gear indicator and media control gestures to the repurposed digital dial. The watch face was secured to the gear stick very carefully, using a 3D-printed mount with tight tolerances.
Don't throw away old smartwatches! 3D printed a custom housing to turn one into a Digital Shift Knob. ♻️🕹️ from r/3Dprinting
The video shared in Desmontei’s Reddit post shows the smartwatch display changing to match the current gear stick selection. It appears to work as expected, but it wasn’t easy to ensure it reliably reported the correct gear selection. The watch’s accelerometer and gyroscope read the angle of the stick to work out what gear the car is in. However, the data can be thrown off when going uphill or downhill, so dynamic calibration had to be added to the algorithm.
Desmontei’s repurposed TicWatch Pro 3 also doubles as an intuitive media controller. When driving, you can change tracks in Spotify with back, forward, and pause swipes on the screen. The techy DIYer intends to add yet more functionality in due course. Specifically, ‘Phase 2’ will link it up “to an OBD2 scanner via Tasker for live telemetry (RPM, Temp).”
For those who might wish to follow in Desmontei’s footsteps, there’s a lengthy (2 hrs) video to check out on the Desmontei YouTube channel. But, briefly, the DIYer “took an old TicWatch Pro 3 smartwatch and carefully cut the original casing with a rotary tool to extract just the OLED screen and motherboard. Then, I modeled a custom shift knob enclosure to house the electronics perfectly.”
The prototype’s tolerances had to be extremely tight “because I didn't want the screen popping out while shifting gears, and PLA was the easiest to test the fitment,” it is explained. If/when this prototype warps or breaks, “I'll use it as an excuse to reprint V2 in ABS or PETG,” Desmontei added. It’s a neat integrated solution, as the design bypasses the watch battery and is wired directly to the car’s 12V electrics.
Another change that may come in V2 could be the use of a second (reference) gyroscopic sensor in the car to make the gear shift position calculations more reliable. Desmontei's other exploits also include PlayStation and handheld modifications, as seen on their website.
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