Page 261 - Robot Builder's Bonanza

Chapter 22

Using DC Motors

DC motors are the mainstay of robotics. A surprisingly small motor, when connected to
wheels through a gear reduction system, can power a hefty robot seemingly with ease. A flick
of a switch, a click of a relay, or a tick of a transistor, and the motor stops in its tracks and
turns the other way. A simple electronic circuit enables you to gain quick and easy control
over speed— from a slow crawl to a fast sprint.
This chapter shows you how to apply continuous DC motors (as opposed to stepping or
servo motors) to power your robots. The emphasis is on using motors to propel a robot across
your living room floor, but you can use the same control techniques for any motor application,
including gripper closure, elbow flexion, and sensor positioning. What follows applies to DC
motors with and without gearboxes attached to them.

This chapter discusses electronic components and circuits related to controlling DC motors. If
FYI you are brand- new to these subjects, be sure to see Chapter 30, “Building Robotic Electronics—
the Basics,” and Chapter 31, “Common Electronic Components for Robotics.”

The Fundamentals of DC Motors

There are a many ways to build a DC motor. By their nature, all DC motors are powered by
direct current— hence the name DC— rather than the alternating current (AC) used by most
motorized household appliances.

THE PERMANENT MAGNET MOTOR: AFFORDABLE, EASY TO USE

Perhaps the most common DC motor is the permanent magnet type, so called because it
uses two or more permanent magnet pole pieces that remain stationary. The turning shaft
of the motor, the rotor (or armature), is composed of several sets of wires— called windings.
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