A servo motor is basically an actuating device which has the ability to know its current state of its output shaft. It is controlled through the control pulses applied to the control wire a method commonly called Pulse Coded Modulation, the output angle of the servo’s shaft is proportional to the pulse width applied on the control wire.
To test servos, hobbyists usually attach the servos to a little contraption where they turn a knob to inject stimulus to the servo. EdwardM shared this simple servo tester which is capable of comprehensively testing any modern servos, Ed included all necessary files to replicate the project.
The simple tester has two pushbuttons, CENTER and SWEEP and a potentiometer. CENTER just like the name suggests it positions the shaft at the center afterwards the potentiometer can then be used to change the shaft’s position while SWEEP goes through the entire angular range of the servo at a rate determined by the potentiometers setting.
The PIC12F675 used its internal timer to set up a constant frame of 20ms, while an ADC channel was used to determine the ON/OFF cycle set at the potentiometer.