CHAPTER 6 ■ ROBOT LINE-FOLLOWINGTwo different colors were chosen so that you can tell which side is lit up even in the dark when the
position of the body isn’t visible. Three LEDs are used so that the indication is visible from any angle.
The Brains
This robot isn’t exactly the smartest cookie in the package. It simply turns on a motor and indicator light
if one set of sensors is brighter, or turns on the other motor and indicator light if the other set of sensors is
brighter.
To accomplish this feat of genius, a chip called a comparator is used (see Figure 6-15). It compares two
signals and flips a switch one way or another. That’s it.
Figure 6-14. Brighter-left indicator LEDs as seen from left-side of robot
Figure 6-15. Comparator (center) flanked by two transistor switches (left and right)
Unfortunately, a motor and three lights consume more power than the comparator chip can provide.
So, transistors provide power to each side of the robot as the comparator directs.
The Muscle
The motors are fixed in a forward position without the ability to swivel for steering. Tiny steering columns
are tricky to make at home and difficult to obtain in the sizes desired for a robot.
However, the robot can control its direction by varying the amount of power applied to each motor.
Power to both motors drives the robot forward. Power only to the left motor causes the robot to turn right,
pivoting around the right wheel. Power only to the right motor causes the robot to turn left, pivoting around
the left wheel.