May 14, 2009


Using Controlling Servos for Your Project

What is a servo?

A servo is a device that acts automatically to set parameters and then send feedback to correct a mechanism's performance. For this, angle positions or other parameters are controlled automatically. As an example, if a car has cruise control, a servomechanism may be controlling, correcting and continually managing it.

If the system as properly configured, the servomotor velocity is going to approximate the velocity signal that the servo drive receives from the control system. You can adjust certain parameters, such as proportional gain, derivative game, and feedback gain to get your bizarre performance. This is also called "tuning."

Servos have an advantage over traditional AC or DC motors because they provide motor feedback. Not only does this ensure that the motion you want is given accurately, but it can also detect and correct unwanted motion, which will give motors a longer lives to ban the nose on typical AC or DC motors. In addition, servos can shunt off electricity that's been generated from the motor itself, also preserving useful life.

In some cases, several mechanisms can use a servomotor, or may not. Household furnaces with thermostats are a good example of this. In this case, though, the feedback is not in a closed loop like it is with cruise control.

Many times, servos provide what's called "position control." Mechanical force is manufactured, often with a motor. Pneumatics or hydraulics can also provide the power.

Today, other systems use servos as well, such as autofocus cameras or hard disk drives.

The origins of the servos

It may surprise you to know that the altar technological servos began with James Watt, the father of the steam engine. He invented the first powered feedback system. The steering engine for a ship was also based on feedback position control, first used in 1866. They had modern servomechanism setups, including input, output, air signal, and amplification of the air signal so that negative feedback could correct the error.

Today, oftentimes, RC servos are used for remote control devices to help you steer and control miniature planes, cars, or boat rudders.

Analog versus digital servos

When servo controllers first became popular, analog controllers were usually used. However, today, digital signal processing and computer technology have made them almost all digital. This has an advantage over analog servos, because as the user, you can do a number of different operations on the digital signals in addition to standard controller options.

Using servos for your own projects

There are a lot of resources available on the Internet that describe how to use servos for your own projects. For example, if you want to begin by building a simple robot, create a controller for your wireless camera, or a number of other projects, you can find these things on the web.

Type in the keywords "servos control digital camera" or a similar keyword phrase to find out the information you want. There are even forums available for those who are very versed in building their own servos.

Some examples

For example, it may be that you're going to be using three ground wires in your servos project, which will be multicolored so as to tell you what they are. The first, will be black or orange, the grounding wire; the second will be read for power, and the third should be brown or another color for control.

Your server will be able to move based on the signal sent over the control wire, which will set the actuator arm to the correct position. In addition comes a servo is going to get a pulse every 20 ms so that it can continually correct the angle. How wide the servo pulse is will affect the range of the angular motion of the servos.


Most servo motors are powered from NiCad batteries, although more environmentally friendly NiMH are becoming more popular. Usually calm your voltage ratings are going to be between 4.8 to 6 V.

Digital servo controllers

Digital servo controllers are becoming increasingly popular because they provide motion control with processed digital signals. Device sensors measure feedback, the current position of your project, and then feedback so that output is given to some type of servomechanism to manage a control signal and make any corrections.

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