CHAPTER 9
Resistors
Sandwich, the line-following robot, uses many resistors on its circuit board (see Figure 9-1). These resistors
are so vital that Sandwich could not operate without them. In this chapter, you’ll learn how to identify,
purchase, and test resistors. In later chapters, you’ll put resistors into use in the same way that they’re used
on Sandwich.
Limiting Power with Resistors
The main water supply hookup to your home is a fairly large pipe. But the pipe leading to your showerhead
is a lot smaller.
Obviously, the smaller pipe saves some space, but it also acts to decrease the amount of water delivered
to that location. You would not be pleased to begin your day with a shower blasting you with the full force
of your water main! (Well, I don’t know you personally; perhaps you could use that much of a shower.)
Besides the displeasure of getting overwhelmed by a watery blast, a lot of water would get wasted.
You don’t need that much water to effectively take a shower.
Resistors limit or divide up the flow of electricity. In doing so, they prevent waste and deliver the
specifically requested amount of electricity to each part.
Obtaining a Resistor Variety Pack
Resistors are so useful and inexpensive that you’ll want to obtain a wide assortment of values. A good place
to start is with a ½-watt, 5% tolerance, carbon-film variety pack (see Figure 9-2).
Figure 9-1. Five resistors on Sandwich’s circuit board