Servo Controller Daughterboards
From PHCC
Servo Controller Daughterboards
RC-type Servo controller
Servos are standard equipment used in radio controlled cars, airplanes, boats,...
Servos are basically a geared down motor with a position feedback sensor. This is usually a potentiometer. RC-type servos usually have three leads: GND, positive supply (4.5-5V), and the control input.
To tell the servo where it should turn, it requires a square wave on the control input. This square wave is modulated (PWM, pulse width modulation). The on/off percentage is called "duty cycle", and the time between the square wave signal "restarts" is called period.
The period for RC servos is around 20ms (18-21ms). The PWM "on time" for one end of the movement range is about 1ms, and 2ms for the other end of the movement range.
Angular movement ranges of servos usually range from about 90 degrees to about 180-200 degrees.