About a year ago I paid about EUR 20 for a WDD35 potentiometer with a linearity of 0.5%. It looks quite beautiful on the inside, with ball bearings and conductive plastic track which is milled to ...

Then he found the very affordable 28BYJ-48 stepper motor. After some experimenting, he came up with a smooth moving robot arm with four steppers controlled from an Arduino Mega and A4988 stepper ...