Page 147 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 6 Options for Creating and Controlling Motion 127

FIGURE 6-3 White arrows show direction of current flow and black arrows show the direction
of the resulting magnetic field in the wire coil

one side will repel the magnet, and the other side will attract it. In order to keep the
wire spinning, we need to turn off this flow of current when one side of the coil is
close to the magnet, or it will get stuck. So by scraping off the insulation on only one
side of the wire, we are telling it to attract, turn off, attract, turn off, attract, and so
on, and the momentum of the coil keeps it spinning!

Types of Rotary Actuators

All motors work under the same principles as our DIY motor, but different motors
accomplish this in different ways. Each motor type in the motor family has pros and
cons, is controlled in a different way, and is well suited to a different set of uses.

The most commonly used type of rotary actuator is the electric motor that spins and
creates rotary, or circular, motion. Figure 6-4 shows the rotary motor family tree. There
are some cousins I left off the tree, but these are all the motor types we’re primarily
concerned with in this book.