Hobby Servo Tutorial from buzai232's blog

Hobby Servo Tutorial

Servo motors are an easy way to add motion to your electronics projects. Originally used in remote-controlled cars and airplanes, they now crop up in all sorts of other applications. They're useful because you can precisely control the positioning of these motors. Instruct them where to point, and they'll do it for you.Get more news about Data Servo Connector,you can vist our website!

An ordinary DC motor has two hookup wires and simply turns continuously when power is applied. If you want it to spin in the opposite direction, you'll need to reverse the power. And if you want to know how far it has turned, you'll need to devise a way to measure that.

In contrast, you instruct a servomotor where to turn using carefully-timed pulses. The servo has three wires: power, ground, plus a third wire to carry the command pulses.

Servo Motor Background
In the most generic sense, a “servomechanism” (servo for short) is a device that uses feedback to achieve the desired result. Feedback control is used in many different disciplines, including speed, position, and temperature.

In the context we are discussing here, we are talking about hobby or radio-control servo motors. These are small motors primarily used for steering radio-controlled vehicles. Because the position is easily controllable, they are also useful for robotics and animatronics. However, they shouldn’t be confused with other types of servo motors, such as the large ones used in industrial machinery.

RC servos are reasonably standardized - they are all a similar shape, with mounting flanges at each end, available in graduated sizes, from "ultra-nano" to "giant". Servos often come with multiple attachments, such as wheels or levers, known as “horns”, than can be attached to the shaft, to fit the device they are operating.

Electrical Connection
Most hobby servos use a standard type of 3-pin plug, with the same control signaling, which makes RC servos reasonably interchangeable.

The connector is a female, 3-pin, 0.1" pitch header. One thing that can be confusing is that the wiring color code isn't always consistent -- there are several color codes at play. The good news is that the pins are usually in the same order, just that the colors are different.
Control signal
The third pin of the servo connector carries the control signal, used to tell the motor where to go. This control signal is a specific type of pulse train. The pulses occur at a 20 mSec (50 Hz) interval, and vary between 1 and 2 mSec in width. The Pulse Width Modulation hardware available on a microcontroller is a great way to generate servo control signals.

Common servos rotate over a range of 90° as the pulses vary between 1 and 2 mSec -- they should be at the center of their mechanical range when the pulse is 1.5 mSec.