Page 280 - Robot Builder's Bonanza

Chapter 23

Using Servo Motors

C motors are inherently an open feedback system— you give them juice, and they spin.
DHow much they spin is not always known, at least not without additional mechanical and
electronic parts.
Servo motors, on the other hand, are a closed feedback system. This means the output of
the motor is coupled to a control circuit. As the motor turns, the control circuit monitors the
position. The circuit won’t stop the motor until the motor reaches its proper point. All without
your having to do anything extra.
Servo motors have earned an important place in robotics. And fortunately for robot build-
ers, another hobby— model radio control— has made these motors plentiful, easy to use, and
quite inexpensive.
In this chapter you will learn what you need to know to use radio control (R/C) servos in
your robot projects. While there are other types of servo motors, it is the R/C type that is
commonly available and affordable, so I’ll be sticking with those only.

Be sure to also check out Chapter 24, “Mounting Motors and Wheels,” to learn how to attach
FYI servos to your bot, and the chapters in Part 7, “Microcontroller Brains,” on how to program
servos to do various wonderful things.

How R/C Servos Work

Servo motors designed to be operated via a radio- controlled link are commonly referred to as
radio- controlled (or R/C) servos, though, in fact, the servo motor itself is not what’s radio
controlled. The motor is merely connected to a radio receiver on the model plane or car. The
servo takes its signals from the receiver.
This means you don’t need to control your robot via radio signals just to use an R/C servo
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