Reference3: Concept

 Concept Reference

Hobby Servo Tutorial: https://learn.sparkfun.com/tutorials/hobby-servo-tutorial/all

Servo motors make adding motion to your electronics projects simple. They were first utilized in remote-controlled automobiles and airplanes, but they've since found their way into a variety of other uses. Because you can precisely regulate the location of these motors, they're handy. Tell them where to point, and they'll take care of it. When electricity is delivered to a standard DC motor, it has two connecting wires and rotates continuously. You will need to invert the power if you want it to spin in the opposite way. 

A "servomechanism" is a device that uses feedback to produce the intended result in the broadest sense. Many other disciplines, such as speed, position, and temperature, require feedback control.

RC servos are quite standardized: they all have the same form, mounting flanges on both ends, and come in graded sizes ranging from "ultra-nano" to "huge." Servos frequently come with a variety of attachments, such as wheels or levers known as "horns," that may be connected to the shaft to customize the device they're controlling.

The control signal, which tells the motor where to travel, is carried on the third pin of the servo connection. This control signal is a pulse train of a specified kind. The pulses are 20 mSec (50 Hz) apart and range in width between 1 and 2 mSec. A microcontroller's Pulse Width Modulation circuitry is an excellent technique to produce servo control signals. When the pulses fluctuate between 1 and 2 mSec, common servos spin throughout a 90° range; when the pulse is 1.5 mSec, they should be at the center of their mechanical range.