Stepper motors use a cogged wheel and electro
magnets to nudge the wheel round a 'step' at a time.
By energizing the coils in the right order, the
motor is driven round. The number of steps that the stepper motor has
in a 360 degree rotation is actually the number of teeth on the cog.
The motor we are using has 48 steps, but then the
motor also incorporates a reduction gearbox of 1:16 that means that
it needs 16 x 48 = 768 steps.
In this lesson, we do not use the common Red
connection. This connection is only provided if you are using a
different type of drive circuit that does not allow the current in
each coil to be reversed. Having a center connection to each coil
means that you can either energise the left or right side of the
coil, and get the effect of reversing the current flow without having
to use a circuit that can reverse the current.
Since we are using a L293D that is very good at
reversing the current, we do not need this common connection, we can
supply current in either direction to the whole of each of the coils.