DIY haptic input knob: BLDC motor and round LCD [video] | Hacker News Reader

DIY haptic input knob: BLDC motor and round LCD [video]

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10 pointsscottbez14 comments

Sharing a little side project I've been working on in my free time (and open-sourced [0]), using a BLDC gimbal motor and a magnetic encoder to create a rotary input knob with all sorts of software-configurable haptic feedback.

You can find gimbal motors for pretty cheap these days, and some of them have hollow shafts, so I was able to mechanically and electrically support a round LCD wired up through the middle of the motor, with no need for a slip ring or anything expensive/complicated.

I also experimented with mounting strain gauges to the main PCB, which has some cutouts so it acts as a little bit of a flexure, for push/pull detection (and haptic feedback "click" provided by a super short torque of the BLDC motor) [1]

Happy to answer any questions you might have!

[0] https://github.com/scottbez1/smartknob/ [1] https://twitter.com/scottbez1/status/1499514054624169993

very interesting. Seen some research prototypes years ago and some references to really fancy equipment with it, but not anything directly DIY-able.

Probably hard to describe, but how much resistance can it actually present? Some others had quite big motors, I guess even with modern BLDCs there's a clear limit of what can be done in that size?

With the motor I'm using the "endstops" feel like a moderate strength spring-loaded return, if that makes any sense? Not a stiff spring, more like pulling on a rubber band?

It's definitely not a hard stop, but still noticeable. You can kind of get a sense for it at 1:06 in the video when I let go of it in Return-to-center mode and it springs back (and oscillates a little from the inertia).

Just checked if it was already submitted because I saw it on twitter. This project is literally a dream, it has so many exciting applications - just imagine as an synthesizer controller with fully interactive haptic feedback. I really need to look into getting hold/building one of those. I wonder how nice this could integrate with virtual reality too, you're often not super aware of the physical surrounding and this could simulate a variety of situations.

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