Keyestudio Smart Little Turtle Robot V3 Manual page 84

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(1) Description
Servo motor is a position control rotary actuator. It mainly consists of
housing, circuit board, core-less motor, gear and position sensor. Its
working principle is that the servo receives the signal sent by MCU or
receiver and produces a reference signal with a period of 20ms and width
of 1.5ms, then compares the acquired DC bias voltage to the voltage of the
potentiometer and obtain the voltage difference output.
When the motor speed is constant, the potentiometer is driven to rotate
through the cascade reduction gear, which leads that the voltage
difference is 0, and the motor stops rotating. Generally, the angle range of
servo rotation is 0° --180 °
The rotation angle of servo motor is controlled by regulating the duty cycle
of PWM (Pulse-Width Modulation) signal. The standard cycle of PWM
signal is 20ms (50Hz). Theoretically, the width is distributed
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