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

[Martin Klang]

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 via Synth-diy <synth-diy at synth-diy.org>
Sent: Friday, June 21 2024, 2:53 pm
To: Benjamin Tremblay <btremblay at me.com>; SDIY List <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Using dual taper (4 pin) pots as encoders ?
 
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
> 
> 
> Benjamin Tremblay
> btremblay at me.com
> Carlisle, MA 01741
> 
> 
> 
> 
> 
> 
> 
> 
> 
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