The Arduino Inventor's Guide (5 page)

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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

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.


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
and the vertical sections on the sides of the breadboard as
, assuming this orientation.

Breadboards come 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
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.

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.

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.


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
, 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

Resistors (left), capacitors (center), and LEDs (right) are examples of discrete components.

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

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.

ADXL345 breakout board with headers


With the concepts of circuits, components, voltage, current, and resistance defined, we can now talk about two different approaches to electronics:
. 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 in response to conditions, whereas analog circuits tend to use components to vary the current, voltage, and resistance of a circuit to achieve the same result.

There are advantages and disadvantages to both ways of thinking, but you can’t solely use one and not the other. For example, you couldn’t read the temperature using a microcontroller without using a number of analog components as well.


is a small computer that you can program by uploading a program or set of instructions. Microcontrollers are used to automate simple tasks, like controlling the temperature of your house or watering your lawn when it’s dry.

The projects in this book use the SparkFun RedBoard microcontroller board, which is 100% compatible with the Arduino Uno. Both are pictured in
Figure 12

The SparkFun RedBoard (left) and the Arduino Uno (right) microcontroller boards

In an average day, you probably use 15 to 20 microcontrollers and you don’t even know it. They are in your coffee maker, alarm clock, and microwave. Your car alone has anywhere from 5 to 10 of them that control the braking, stereo, and ignition systems. Our world practically runs on microcontrollers. This book will help you learn how to harness that fact to take back a bit of control over your world.


You will learn more about the Arduino, how to program it, and what its capabilities are as you build the projects. For now, just know that a microcontroller is a programmable brain that makes electronics easier for anyone to build and prototype ideas that automate the world around them.

We hope that this short primer has given you a little background and a preview of what the rest of this book will cover. We’re excited that you’ve decided to embark on this adventure with us. Now, let’s get to building our first project!

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