CHAPTER 18
Adding Gearhead Motors
In this chapter, we will select and install motors in the line-following robot circuit. You’ll also learn a little
about diodes.
Selecting Gearhead Motors
In choosing motors for the line-following robot, consider the following criteria:
- The motors should operate at voltage ranges provided by a 9 V battery. That’s slightly
less than 10 VDC, down to 7 VDC. - The motors should be small enough to fit abreast within a sandwich container.
That means each motor may be no more than 6 cm in length and 4 cm in diameter.
Motors with smaller dimensions are even better, as you can add tubes or other
ornamentations. - The loaded motor speed should not be so slow as to bore people, but not so fast as
to drive the robot off of the course. Depending on the wheel size, this equates to
rotational speeds of roughly between 50 RPM and 125 RPM. Such slow rotation at 9 V
requires a gearhead motor. - The motor must not draw more than 500 mA of current at any time, because that’s
the maximum the 2N2907A transistor can support.
There were a couple of additional criteria I considered:- Because the motors are integral to a project that you can build yourself, I selected
motors that are available to consumers in small quantities. - Because the motors appear in my book, which will be available for years, I selected
motors that are currently in production and are available from a major supplier.
(This ruled out surplus sales.)
Obtaining the Gearhead Motors
The motors selected are 12 V, 225 RPM gearhead motors made by Hsiang Neng (see Figure 18-1). The motors
are rated at voltages from 4.5 V to 12 V, which is perfect for a 9 V battery.