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DIY haptic input knob: BLDC motor + round LCD

scottbez12 HN recommenders · recommended in 2 months, 2023–2026
YouTube
demo · intermediate · evergreen · 2023–2026 on HN

A two-minute demo of SmartKnob View, an open-source input knob built from a brushless gimbal motor, magnetic encoder and round LCD. Closed-loop torque control gives software-defined detents and end stops.

HN people hold it up as a polished solo hardware project and the go-to example of haptic knobs, including in discussions of physical car controls.

6 comments from Hacker News

@laurencei2024-07 · in “Reverse-engineering my speakers' API to get reasonable volume control”

Hey OP - if your thinking about a smart knob with haptic feedback etc - check this open source project out that you can build yourself - its amazing: link Video demo here: ▶ this video

Strongly recommends View on HN
@rzzzt2025-06 · in “Ask HN: What Are You Working On? (June 2025)”

Vaguely related - two encoder wheel projects on YouTube that might interest you: - "Wireless High Resolution Scrolling is Amazing": link - "DIY haptic input knob: BLDC motor + round LCD": ▶ this video

Recommends View on HN
@crote2026-05 · in “Mercedes-Benz commits to bringing back physical buttons”

I'm not convinced it is that easy. Cars traditionally have very generic button clusters, like [0]. It is even very common to have dummy buttons in there. Combine that with today's cars where those buttons are hooked up to some MCU to send a CAN message instead of being hardwired to a function-specific cable in a giant loom, and it is suddenly quite easy to change button functionality quite late in the design process for basically zero cost: you just need a slightly different label print and a small firmware patch! Or, if you want to be 100% flexible, go with the ATM approach where physical buttons are placed next to an icon shown on a screen[1]. All of the flexibility and all of the tactile feedback! You can even go for a multi-level layout, with a top row of mode selection buttons, a bottom row of mode-specific function buttons, and perhaps even a big fat dial with haptic feedback[2]. Or even go all-out Elgato Stream Deck[3]. And sure, the fact that slapping in a giant touchscreen lets them decouple UX design from physical controls is going to play a big role. But it is by far the laziest and least user-friendly way of doing so. If that's the best you can come up with, you probably shouldn't be doing UX design at all. [0]: link [1]: link [2]: ▶ this video [3]: link

@yonatan80702023-11 · in “Tesla Normal Operating Sounds”

This reminded me of the SmartKnob View I saw on YT a while back, it's a knob built on a burshless motor that's controlled to provide the user with software defined feedback like tactile clicks and end stops ▶ this video

@scottbez12023-08 · in “Ask HN: What's the coolest physical thing you've made?”

I made a rotary input device that provides software-defined "virtual" detents and end-stops, implemented using a BLDC gimbal motor. It can dynamically switch from completely smooth unbounded rotation, to having detents with configurable spacing and strength and "end-stops" that spring back if you try to rotate past them. ▶ this video It's got a round LCD on the front of the knob (wired and supported via the hollow shaft of the motor) and uses the flex of the PCB and strain gauge sensors (in the latest revision, simply SMD resistors whose resistance changes when stretched) to detect when the knob is pressed down. It's open source hardware and software - link HN folks might appreciate that it communicates with host software on the computer via protobuf-encoded USB serial messages -- nanopb is awesome for embedded C protobuf support, and having the defined schema, autogenerated serialization code, and compile-time type safety is so much nicer than ArduinoJson or hand-written binary protocols! I'd love to get it hooked up to some real software eventually (video editors or home-assistant control are my 2 main ideas), but it's really just been a fun project to tinker with and try out some new ideas and parts I've never used before.