Controlling a Stepper Motor with Arduino

For a four-wire stepper motor, you need two full-bridge power drivers, one for each winding.

Also, due to the inductance of the windings, for anything other than extremely low speeds, they must be driven from a high voltage supply using constant current drivers.

The simplest approach is to use one of the readily available stepper motor driver modules such as these:

There are arduino libraries for controlling steppers using modules such as those.

The motor supply to the driver module should be somewhere in the 12V - 24V range.

The modules also include microstepping, so the motor can be positioned to an accuracy of eg. 1/16 it's full step angle.

For controlling a stepper motor like the 42BYG with an Arduino, you might want to check out the A4988 or DRV8825 stepper motor drivers. They’re pretty easy to work with and give you precise control over stepping. Just connect them to your Arduino, and you’ll be able to step the motor one step at a time.

Sorry for what could be a stupid question: what other options do exist besides "one step at a time".