[sdiy] Using dual taper (4 pin) pots as encoders ?

[brianw]

Thanks Martin and Roman. It's always interesting to learn about unique parts - especially when actual part numbers are shared.

Brian

On Jun 21, 2024, at 6:11 AM, Martin Klang wrote:
> aka Endless potentiometer, with two outputs in phase quadrature. The Alpha RV112FF-40 is the only commercially available example that I know of.
> 
> Martin
>  
> -----Original message-----
> From: Roman Sowa
> Sent: Friday, June 21 2024, 2:53 pm
>  
> Quadrature potentiometer.
> One taper is rotated 180 or 90 degrees versus the other one. This way at 
> any angle there's at least one wiper on its taper. Basicaly a way to 
> remove the dead spot, where wiper travels over empty fragment between 
> taper ends.
> Measure 2 voltages, a bit of calculations and you have rotary encoder 
> with resolution as high as your ADC.
> 
> Roman
> 
> W dniu 2024-06-21 o 13:34, Benjamin Tremblay via Synth-diy pisze:
> > Hi, another MCU question.
> > I have noticed many synth manufacturers have used 10K 4-pin dual 
> > potentiometers as “encoders”. I’m assuming that these are feeding a 
> > multiplexed ADC.
> > My question is, what is the secret sauce? Are both pot tracks wired 
> > differentially to reduce noise? Does this indeed go into an ADC or is 
> > this some clever way to approximate a rotary encoder but have the smooth 
> > motion of a pot?
> > 
> > If using a 4-pin potentiometer is a way of achieving a more stable and 
> > reliable mass-production of control knobs, I’m very interested.
> > 
> > Thanks,
> > Ben