The Arduino Inventor's Guide Read Online Free

change the water pressure in the hose. The water pressure in the hose is similar to the voltage in a circuit. If you increase the waterpressure, the flow also increases. This is the same with circuits: if you increase the voltage, the current also increases. The final part of the analogy is in the hose itself. If we put a kink in the hose or restrict its diameter, we create resistance. The increase in resistance slows down the flow (lowers the current).
    This model works pretty well to describe the flow of electricity, but you don’t want to set up this whole system of hoses, valves, and pipes to just let water run out onto the ground (unless your goal is to water the lawn). You want to do something with it; you want it to do
work
. In terms of circuits, we use devices that change electricity into other forms of useful energy, such as illuminating a light, rotating a motor, or sounding a buzzer. A device that converts electrical energy to other forms of energy is called a
load
. Thomas Edison discovered that he could convert electrical energy into light energy with the light bulb; you will do that and a whole lot more throughout this book.
SCHEMATICS, CIRCUIT BLUEPRINTS, AND WIRING DIAGRAMS
    While pictures are nice, it’s not efficient to meticulously draw out every component to show how a circuit is wired up. Throughout the book, you will see
schematics
like the one in Figure 3 as well as illustrations to help you with your circuits.
    FIGURE 3: This simple schematic shows a battery, an LED, and a resistor.

    Schematics are simplified drawings of circuits. We sometimes also call these
wiring diagrams
or
circuit blueprints
. A schematic shows what is connected to what and which components to use in building the circuit. We will use the IEEE (Institute of Electrical and Electronics Engineers) US standard for drawing circuits in this book. The schematic in Figure 3 actually represents the same circuit as the illustration in Figure 1 . The straight lines represent wires, and each component has its own unique symbol. Figure 4 shows some common schematic symbols you’ll see in this book.
    FIGURE 4: Some standard IEEE schematic symbols

    The IEEE schematic symbol format is internationally recognized and used to communicate and share circuit drawings across the world. It’s intended to quickly represent components using very simple lines and drawings.
PROTOTYPING CIRCUITS
    As you work through the projects in this book, you will build and test a variety of designs. As you build a circuit, you may also want to rearrange parts, swap things around, or add new components. This process is called
prototyping
. You can prototype electronics in a way that is similar to building with wooden blocks or LEGO bricks by using a
solderless breadboard
like the one shown in Figure 5 .
    FIGURE 5: A translucent solderless breadboard with horizontal rows and vertical power rails

    A solderless breadboard is a plastic rectangle with a lot of holes in it. These holes are spaced on a 0.100-inch grid and sized so that the majority of electronic components fit snugly in them.Underneath the holes are small clips made out of a soft conductive metal, as shown in Figure 6 .
    FIGURE 6: The innards of a solderless breadboard (left) and a close-up of the metal clip inside (right)

    Wires that are plugged into holes on the same row are connected together electrically by these metal clips. It’s like twisting the wires together without the twisting part. Notice that the clips only span the width of five holes. There is a center “ditch” that divides the two halves of the breadboard, and the clips on the right side are not connected to the clips on the left side.
    NOTE
    Hold the breadboard so that it is tall and skinny (portrait orientation) and the letters at the top are right side up. We’ll refer to the horizontal groupings of five holes as
rows
and the vertical sections on the sides of the breadboard as
columns
, assuming this orientation.
    Breadboards come