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

[Roman Sowa]

If you need just one for DIY project, you can make it yourself.
There are dual pots where tapers are facing each other, and wipers 
rotate between them. This one is the easiest (if not the only possible) 
to adapt. Open the holding tabs, rotate external plate by 180 deg and 
cut the rotation-limit detent.
It may not have very long durability, but is cheap, quick and you don't 
have to buy 1000 minimum quantity.
Attached picture says it all.

Roman

W dniu 2024-06-21 o 16:58, Benjamin Tremblay pisze:
> Yes Roman! That must be it.
> It’s not what I would think of as a “stereo panpot” with six leads.
> And how would I shop for one)
> Benjamin Tremblay
>
>> On Jun 21, 2024, at 9:29 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
>>
>>  I hope the mounting height matches some other useful hardware!
>>
>> Trying to find pots that match the rotary switches, encoders, or 
>> buttons you have is very difficult.
>>
>> Tom
>>
>>> On 21 Jun 2024, at 14:11, Martin Klang via Synth-diy 
>>> <synth-diy at synth-diy.org> wrote:
>>>
>>> RE: [sdiy] Using dual taper (4 pin) pots as encoders ?
>>> 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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>>
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