Servo - Servo Basics

Servo - Servo Basics - HOBBY HOBBY SERVO FUNDAMENTALS BY:...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
HOBBY SERVO FUNDAMENTALS BY: DARREN SAWICZ
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
I NTRODUCTION obby servos are a popular and inexpensive method of motion control. They provide an off-the-shelf solution for most of the R/C and robotic hobbyist's needs. Hobby servos eliminate the need to custom design a control system for each application. Without hobby servos (hereafter referred to only as servos) you would have to: design a control system analyze the transient response fine tune the feedback loop determine the proper gear ratio for the desired speed or effi ciency choose a motor build the mechanical sections build the amplifier and motor driver try to make it fit inside what ever you're trying to control! Although servos are very common, technical information is hard to come by. A search of the Internet will bring up bits and pieces but it is hard to locate a single source for all the information. In this document I will attempt to provide all the information you would need to hack a servo or make your own. S ERVO B ASICS hroughout this document I will be using the Tower Hobbies TS-53 servo to describe how servos work. Other servos may be a different size or have metal gears or bearings but the basic concept of operation is the same. Since the early 1990's servos have used a de-facto standard pulse width modulation technique to control the position of the output shaft. The pulse is fed to the servo via a control line. The control line does not supply power to the motor directly it is an input to a control chip inside the servo and as such it does not have to supply much current to the servo. Consequently if you are designing a servo controller you may use just about any technology (CMOS, TTL, Discreet Components) to drive the control line. A separate power wire supplies the power to the servo. The ground for power is also used as the ground for the control line. Although there are only three wires, manufacturers haven't standardized the pinouts. Most connectors are wired the same but there are H T
Background image of page 2
FIGURE 1: SERVO CONTROL TIMING 1ms (Minimum Required Time) The servo is positioned to the extreme left. 2ms The servo is positioned to the extreme right. 1.5ms The servo is centered. exceptions like the Airtronics connector where the power and ground wire is reversed. Connecting a servo that is wired incorrectly can blow your servo or fry the receiver or both. Most servos can be rewired simply by lifting the plastic tab holding the pin into the connector, pulling the pin out the back, and reinserting the pins in the proper place. The power wire carries the majority of the current to the motor. The current varies from almost nothing (9.6mA for the TS-53) when the servo isn't receiving any control signals, to a maximum current when the servo is fully loaded (600mA for the TS-53).
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 02/08/2012.

Page1 / 11

Servo - Servo Basics - HOBBY HOBBY SERVO FUNDAMENTALS BY:...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online