there's something unique about this potentiometer.
it has three large ball bearings in the back, but what for? (read on!)
the three ball bearings form a planetary "gear" reduction, turning this into a 10-turn potentiometer!
the parts.
here are some approximate dimensions. you can't use the regular planetary gear formulas because this setup has no teeth. ball bearings are 7.9mm diameter but this isn't important.
turns of the carrier (which moves the potentiometer wiper) = turns of the "sun" (potentiometer shaft) * S / (R+S) where R is the ring circumference and S is the sun circumference. since there's no teeth, i'm using the circumference as a stand-in.
(diagram is wrong, shaft diameter is actually 1.55mm)
anyway, do the math, and for 1 full turn of the potentiometer wiper, you get about 12 turns of the input shaft.
of course, the potentiometer wiper never does a full turn. more like 300 degrees or so. therefore 300/360*12= 10 turns.
the thread that inspired this one:
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