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

[brianw]

There were a lot of questions here.

As for a rotary encoder with the smooth motion of a pot, you can order encoders like this. You might not find them at amateur resellers like Adafruit, but if you go to the manufacturer web site and browse their product data sheets, you'll find that encoders are sometimes available with two different detents (twice as many or half) or without detents at all. There are also other options like threaded versus non-threaded, and drawings with all of the pertinent dimensions for PCB layout and mechanical design and assembly.

As for stable and reliable, one of the biggest factors is to use the shield that comes with nearly all pots and encoders. Be sure to plan your PCB layout so that the pins from the shield go to chassis ground or an appropriate ground. I've helped people with designs that were super noisy, and all they had to do was connect the shield to ground and that gave a much more stable reading.

Brian

p.s. I have seen some small-time manufacturers use stereo faders, and just connected both wipers. That way, if one wiper fails, then hopefully the other will still be working. But I think their primary motivation was that bulk discounts on stereo faders was cheaper than anything else.


On Jun 21, 2024, at 4:34 AM, Benjamin Tremblay wrote:
> 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