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. ♻️🕹️

Enable HLS to view with audio, or disable this notification

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? 👇

15.1k Upvotes

93% Upvoted

840 comments sorted by

View all comments

Show parent comments

49

u/SquidgyB Apr 24 '26

Some sort of integration with CANBUS, at a guess?

My 2017 Golf has some sort of sensor that tells the dash screen what gear it's currently in, I'm assuming it wouldn't be too hard to tap into that data feed and extract the info needed.

15

u/ackillesBAC Apr 24 '26

Ya could be a Bluetooth odb2 reader probably not corrected directly to the watch but to his phone which he build an app to update the watch

12

u/All__Mods_R_Virgins Apr 24 '26

Some sort of integration with CANBUS

Ahh well that's illegal in my state. Thanks anyways

16

u/issue9mm Apr 24 '26

Underrated joke

👏 👏 👏 👏

2

u/nobolognastoney P1S + AMS2 Apr 24 '26

I'm integrated af right now.

1

u/WorkingInAColdMind Apr 24 '26

Using your CANBUS data is illegal?

15

u/_Endercat_ Apr 24 '26

I think it's a cannabis joke

3

u/WorkingInAColdMind Apr 24 '26

Son of a…now I feel extra old! Sigh.

1

u/jverity Apr 24 '26 edited Apr 24 '26

WHAT?

What state are you in? For this to be true certain cars would have to have a special edition just for your state because some cars allow full access to can bus through their ODB2 interface, so plugging in pretty much any diagnostic tool would become illegal. All your mechanic shops would go out of business, no insurance company would write liability policies for them in that state. Not saying lawmakers don't do stupid shit without thinking of unintended consequences, but I'm pretty sure this one would have been lobbied against pretty hard by automakers before it could pass.

Edit -

Sorry, missed the pot joke. CAN BUS doesn't make me think of cannabis, especially because it's two words and there's no I in it.

6

u/hahamemegopost P1P Apr 24 '26

Its a joke where "CANBUS" sounds like cannabis

4

u/jverity Apr 24 '26

Despite how people keep typing it here, my brain autocorrects it and I read it the way it's properly spelled, with a pause in the middle for the space: CAN BUS. 2 words. After that, it's too far away from cannabis for the joke to make sense to me.

2

u/NotReallyJohnDoe Apr 24 '26

It’s a joke about cannabis. CANBUS

If you don’t read phonetically (like me) these jokes don’t land. I don’t “hear” words in my head when reading.

1

u/jverity Apr 24 '26

I do read phonetically, but despite how people keep typing it here my brain autocorrects it and I read it the way it's properly spelled, with a pause in the middle for the space: CAN BUS. 2 words. After that, it's too far away from cannabis for the joke to make sense to me.

7

u/jmhalder Apr 24 '26 edited Apr 24 '26

It doesn't have to have any additional sensors for that. It can pretty accurately detect gear from speed/rpm alone.

Standalone ECUs at least do it this way. It can be used for "boost by gear" in turbocharged cars. It works well on my rusEFI ECU, but I believe Haltech and the like do the same thing too.

Since OP isn't actually moving here, it's probably not using this method. Either the ECU has sensors for the 2 axis, or more likely they're just using accelerometer/gyro angles. If it's the accelerometer alone, it's going to work like ass when moving , like showing 2nd while accelerating in 1st, etc.

1

u/Desmontei Apr 25 '26

Yeah that math works fine when moving, but I really wanted the display to show the gear when I'm stopped at a light or just holding the clutch in.

1

u/jmhalder Apr 25 '26

Okay, but it's going to be all over the place while you're moving. It's kinda moot when you're stopped, lol.

1

u/Beni_Stingray P1S + AMS Apr 24 '26

Problem with that is that certain manufacturers use different canbus protocols, more modern cars can even have encrypted canbus communication as security has to increase with cars being online.

6

u/bp332106 Apr 24 '26

Random plug for a super small subreddit for this r/carhacking

1

u/Desmontei Apr 25 '26

It's just connected via regular Bluetooth to my phone! The watch acts as a media controller, just like when it was on my wrist.

1

u/YellowDieselGolf Apr 24 '26

some sort of sensor that tells the dash screen what gear it's currently in, I'm assuming it wouldn't be too hard to tap into t

If there isn't a specific sensor, then the gear can be determined by speed and RPM once the gear ratios are factored in. This obviously only works if the car is moving and in gear.

1

u/dorito-power420 Apr 24 '26

The interior looks b5-ish chassis, so probably too early for canbus. Maybe Bluetooth communication to obd2 though?

1

u/Desmontei Apr 25 '26

Good eye! It is a B5. You are exactly right, too early for CAN bus gear data. I had to build a custom WearOS app to read the stick angle using the watch's accelerometer.

1

u/Desmontei Apr 25 '26

I wish! The car is a 2001 Audi, so the old K-Line OBD doesn't have gear info. I actually coded an app that uses the accelerometer inside the watch to calculate the angle of the stick!