The Arduino Inventor's Guide Read Online Free Page A

in a number of shapes and sizes, but most will still have vertical columns on the outer edges of the board. These columns are called
power rails
or
power buses
, and each has a single continuous clip that is connected from top to bottom, as in Figure 7 . Breadboards also often have + and – labels to indicate where to plug in your power connection, with matching red and blue color coding.
    FIGURE 7: Underside of a breadboard, showing both horizontal rows and vertical power rails

    You can see a solderless breadboard in action in Figure 8 , which shows a prototype design of a circuit with eight LEDs.
    FIGURE 8: Circuit on a breadboard

    In this book, you’ll build circuits with solderless breadboards so that if you make a mistake, you can easily change or fix it, and if you want to explore something further, you can quickly add to the circuit. When you start making bigger and more complex circuits, we suggest that you have multiple breadboards around so that you can build circuits in chunks. This allows you to build and test each part of your project incrementally without having to rework, troubleshoot, or take an entire project apart when something doesn’t work.
DISCRETE COMPONENTS VS. BREAKOUT BOARDS
    We mentioned components earlier and want to touch on them briefly here. There are hundreds, if not thousands, of different electrical components in the world. When we say
components
, we are talking about
discrete components
—the most rudimentary parts you can buy. For example, the resistor, capacitor, and LED in Figure 9 are discrete components.
    On the other hand, a
breakout board
is an assembly of components prewired together onto a single board made to be breadboard friendly. Breakout boards help speed up the prototyping process. You can see a good example of one in Figure 10 .
    FIGURE 9: Resistors (left), capacitors (center), and LEDs (right) are examples of discrete components.

    FIGURE 10: A single, tiny accelerometer (left) and its breakout board (right). Notice the plated-through holes on the left side of the breakout board.

    Figure 10 compares a complex component—an integrated accelerometer sensor package (P/N ADXL345 from Analog Devices)—and the breakout board SparkFun produces for it. The chip measures a mere 5 × 3 mm! It has tiny metal connection pins that serve a similar purpose to the long metal legs you see on discrete components. They’re just so small that connecting wires directly to them is nearly impossible. Breakout boards route these small connection points to
plated-through holes
on the edge of the board, spaced exactly 0.100 inch apart so that the holes on the board line up with the holes on a solderless breadboard. Each hole is metal plated so that you can solder wires directly to it. Or, if you want to use it with a breadboard, you can also solder on male headers as shown in Figure 11 . (Don’t worry if you’ve never soldered before; see the instructions in “ How to Solder ” on page 302 .)
    Notice that the holes are each labeled with a silkscreen so you know how to connect the sensor. Breakout boards have these so you can use them immediately on a breadboard without the hours of researching and building you’d have to do to use the bare component on its own.
    FIGURE 11: ADXL345 breakout board with headers

ANALOG VS. DIGITAL
    With the concepts of circuits, components, voltage, current, and resistance defined, we can now talk about two different approaches to electronics:
analog
and
digital
. These approaches are not mutually exclusive, and you can’t really understand the circuits you build without understanding both concepts.
    Analog deals with values that vary within a set range. Think of the dimmer switch in some dining rooms; that is analog. Analog values can be on, off, and anything in between. Digital values, on the other hand, have only two states: on or off.
    Digital electronics tend to include a microcontroller or microprocessor that is programmed to turn things on and off