Due to the relatively small size and shape of a knob, some portion of its internal circuitry is placed close to its external metal controller ring (bangle), making the circuitry vulnerable to electrostatic discharge (ESD). This disclosure describes techniques to establish a dedicated ESD pathway between electrical parts in relative motion (e.g., a controller bangle around a knob and the electronics housed within the knob) by using a spring-like metal structure comprising conductive bristles to receive electric charge from the bangle and to conduct it to ground via a trace on a printed circuit board (PCB) within the knob. ESD current is deflected from sensitive electronics and prevented from damaging it. The ESD current is carried away from the bangle to the PCB by conductive bristles, such that the smooth rotary movement of the bangle is unaffected and occurs without the production of unwanted noise or vibrations.
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Walunj, Sameer; Dong, William; Pan, Weifeng; Pacifico, Daniel; and Huang, Jingyu, "Ground Spring with Electrically Conductive Bristles", Technical Disclosure Commons, (May 09, 2023)