SG90 Servo is an electric motor with a gearbox that can be rotated by a predetermined angle.
Device Servo .
SG90 Servo can be divided into 3 parts: engine, gearbox, control board.
engine - a small, capable of rotating at a constant speed in both directions.
Reducer - a mechanical gear unit, which reduces the speed of the motor, and transmits the rotation of the output shaft. By reducer connected variable resistor for determining the current crank angle (feedback). Also, gear limits the maximum angle of rotation of the engine due to the pin.
Fee Management - converts the input command to the control signal for H Bridge , which connects the motor to the power supply (to rotate left or right). Reads the board with a variable resistor on the gearbox and compares the value to the team. Further calculates the difference and determines which way to rotate the engine to reduce the difference.
SG90 Servo has three wire connection:
To manage servo must be a control wire send pulses with a period of 20 ms (50 Hz). Angle is set duration of the control pulse. Adjust the pulse by using the software or use a timer.