I know the title is phrased terribly, but I'm not sure how to phrase it since I'm not sure of the name.

I have a servo, that I cannot connect to, except for the output spine/shaft (physically). I need to get the output of that servo into an arduino, or raspberry pi. So I need some kind of peripheral that can attach to the shaft of the servo, and tell me what position it's in. I can't figure out how to find what part I need, because I can't google for the name of it correctly. I've tried servo input shaft, and many other things that don't make sense.

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More Info.

I have a servo on a machine, and I can not interface with this servo in any way but physically. I can't read the output from it electronically, and the signals are proprietary. I can't take anything apart, all I can do is put something physically on it.

So, the issue is, I need to (based on nothing but the position of the servo shaft) figure out what position that 3rd party servo is at.

With that information, I'm then going to man in the middle, and attach another servo to my device, and change the value to what I want.

So if the factory servo is at 50%, and I know that by using something like a rotary encoder, if that ends up being the answer, I then could add x% to my actual servo.

  • 1
    google rotary encoder
    – jsotola
    Apr 6, 2020 at 3:13
  • please provide a clear description of what you are trying to achieve ... why would you need position feedback from a servo? ... the servo actuator can already be commanded to move to specific angles
    – jsotola
    Apr 6, 2020 at 3:14
  • @jsotola I'll edit the question now to explain. Apr 6, 2020 at 3:38
  • @jsotola You should write the rotary encoder as the answer, because this is exactly what I needed to know. Thank you so much! Apr 6, 2020 at 3:51

1 Answer 1


What you need is an absolute rotary encoder.

It will provide feedback about the absolute rotational position of the servo shaft.

An encoder that uses gray code is preferred because only one binary bit changes between adjacent positions.

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