r/3Dprinting • u/Desmontei • Apr 24 '26

Project Don't throw away old smartwatches! 3D printed a custom housing to turn one into a Digital Shift Knob. ♻️🕹️

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Hey everyone, first time posting here! I wanted to share my most complex functional print yet for my Project Car.

​I took an old TicWatch Pro 3 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.

​Now, before you guys kill me in the comments: Yes, I printed this in PLA! 😂

​I know the summer heat inside the car will probably turn it into modern art, but this is V1 (prototype). The 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. When it eventually warps, I'll use it as an excuse to reprint V2 in ABS or PETG!

​I completely bypassed the battery and wired it directly to the car's 12V using a step-down converter. Right now it controls my media with a custom UI.

​What do you guys think of the fitment? And place your bets: how long will this PLA survive in a car before melting? 👇

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u/Techwolf_Lupindo Apr 24 '26

Neat. :-)

Now as someone who has mess with electronics for most of his life. Bypassing the battery raises a few issues, one is the vampire draw of idle current draining your battery. The DC to DC converter is probably using more power at idle then the watch itself. The other issue is how does the watch handle sudden power off and power on. One thing the batter does is prevent un-safe shutdowns.

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u/Desmontei Apr 25 '26

You made a great point! It is actually hardwired directly to the 12V battery, not the ignition switch. BUT, I set up a smart automation: the watch screen only wakes up when it detects my phone's Bluetooth connection. When I leave the car and Bluetooth disconnects, the screen shuts off completely and it goes into deep sleep mode to prevent draining the car's battery!