RC Servo Theory

The control signal for an RC Servo is a digital pulse train that looks something like this:

Here, the width of the “high” pulse, t, determines the angle of the rotor. The width, measured in time, will be in the range of

$0.3ms\leq t\leq 2.5ms$

And the frequency of the pulses, given by

$f={\frac {1}{T}}$,

is around 40-50Hz (T ≈ 20ms).

For a practical circuit, see 555 Servo Circuit.