So…take a circle and put a small hole in one side
Place light(led) mounted so that as circle rotates light will shine through at each 360 rotation
Use sensor to detect light so now you know when it has rotated 1 turn(360)
Maybe 1 turn is too much so let’s add 30 evenly spaced holes along circles edge. You now have 30 positions for the circle
Attach circle to motor and AC knob to control rotation by motor….use light sensor to detect position 1-30 and stop/start motor accordingly
This is basically how it’s done but you’ll need to hack together the needed parts. Maybe a stepper motor already does this easier but I forget
Same can be accomplished with magnet and reed sensor or potentiometer
Hope that’s at least gives you and idea
EDIT
Since it has remote…there are several of the shelf items that do IR and RF control and will be easier than physical control
I’d bet you can do IR control from headphone jack of raspberry pi
Or GPIO
or Broadlink seems to be the way to go for IR