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
And the frequency of the pulses, given by
is around 40-50Hz (T ≈ 20ms).
For a practical circuit, see 555 Servo Circuit.