LEGO MINDSTORMS Robots, Manual, Page: 40 / 226

In this chapter, you'll build Trusty, a simple robot that exhibits a behavior called line following. This means that Trusty, shown in Figure 3-1, can drive along a sort of ''track" defined by a thick
black line on the floor. Your RIS kit includes a "Test Pad," which is simply a large piece of white paper with some black lines and other marks on it. Trusty will follow the large black oval on this
paper faithfully until he runs out of battery power.
Figure 3-1.
Trusty, a line follower
As you can see in Figure 3-1, Trusty's main feature is a downward pointing light sensor. This sensor is the key to line following. The light sensor can distinguish between the white background of
the Test Pad and the black line drawn on it. As
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you'll discover, this feature doesn't make line following easy to program; but it does make it possible.
Building Instructions