After some experimenting, he came up with a smooth moving robot arm with four steppers controlled from an Arduino Mega and A4988 stepper motor drivers.

grbl is stepper motor controller firmware for three-axis cnc machines, intended to run on Arduinos with a motor driver add-on board. Engineer in Wonderland cnc-related blogs are indexed here It is the ...

[Christian] had the bright idea that a stepper motor could be driven via the mains, simply by using a capacitor to offset the waveforms on the coils by 90 degrees.