Electricity

Battery-powered versus 120 volts+
One other thing that we made a conscious
decision about when writing this book was that
we didn’t want you tinkering with high-voltage
projects. Electricity can be dangerous! Keeping
to about 6 volts keeps you reasonably safe
whereas working with something that uses 120
volts — like the juice that comes out of your
wall socket — can kill you. While you’re discovering
the basics of electronics, our advice
is that it’s better to be safe than sorry.
When you get more comfortable and more
knowledgeable about tools and skills and safety
measures (which we put a lot of emphasis on,
especially in Chapter 2), you might explore
higher-voltage projects such as high-powered
audio or ham radio projects. In this book, we
show you how to work with low-voltage batteries
and still have fun in the process.
What Can You Do with
Electronics Projects?
You get to explore a number of variations in the projects in this book. And
sure, this stuff sounds like it might be cool, but what’s in it for you?
Electronics projects offer three benefits (at least):
Fun
The thrill of making something work all by yourself
A boatload of useful knowledge
Just for the fun of it
One obvious benefit of tinkering with gadgets is that it’s just plain fun. If
you’re the type who’s intrigued by how things work and what’s under the
hood, you probably already know this.
In fact, we have lost ourselves for hours figuring out circuits (this is the electronics
equivalent of a jigsaw puzzle, which starts as a drawing, like the one
shown in Figure 1-1), wiring the components, and refining the results. You can
also, quite literally, amaze your friends with the things you build. And if you
go in for electronic gizmos that you can race, scare people with, or use to
entertain crowds at parties, you can share the fun with others.
Don’t forget the social aspect: Electronics projects devotees comprise a
friendly bunch of folks who like to help each other. You can get into discussion
groups online or join a local electronics club and find both interesting
ideas and friendships at the same time. Chapter 16 provides ten great Web
sites about electronics where you’ll find such online groups.
10 Part I: Project Prep
2 8 1
4
-
+
R1
6 V +
-
+
-
3
2
1
4
8
3
6 8
7
4
-
+
+
-
5
6
7
4
8
5
S1
+6V
C1 R2
R3
R4
R5
R6
½ IC1
C2
C3
R7
R8
R9
R10
½ IC2
R11 R11 R13 R14
R15 R16 R17 R18
LED1 LED2 LED3 LED4
Q1 Q2 Q4 Q3
Q5 Q6 Q7 Q8
LED9 LED10 LED11 LED12
LED 13 LED 14 LED 15 LED16
½ IC2
½ IC1
+6V
C4
R19
+6V
R20
R21
R22
R23
R24
C5
R25
C6
R26
R27
R32 R33
R28 R29 R30 R31
R34 R35
LED5 LED6 LED7 LED8
+
+
Figure 1-1:
The
schematic
for the
Dance to
the Music
project in
Chapter 5.
Chapter 1: Exploring the World of Electronics Projects 11
Building things you can actually use
So why, when you can buy an AM radio for $7.95, would you decide to build one
yourself with parts that cost $30? That’s a good question. The truth is just about
everything you build in the projects included in this book — and most of the circuits
floating around on the Internet — is something that you could probably
buy in some form somewhere. But where would the challenge be in that?
Here’s why hundreds of thousands of electronics junkies build instead of
buying: Because they can. They can make something that grabs music out of
the airwaves or sets off a light display or sends a little cart wheeling around
the room themselves. We guess this is why people knit sweaters instead of
buying them or work on old cars instead of taking them to mechanics. It just
feels good to master something on your own.
Parts II, III, and IV of this book are where you can find all these cool projects,
divided into categories by what the projects do, such as producing light,
sound, or motion.
Some of the things that you build in this book are just for fun, like the dancing
dolphin light display (Chapter 10). Other things have a practical use: the
Couch Pet-ato (Chapter 14) keeps your cat off the furniture when you leave
the house, for example.
Besides building gadgets that have a use, in some cases, you can build items
more cheaply than you can buy them in the store. You could just end up with
projects you can put to work and save a few bucks in the process.
Picking up lots of cool stuff along the way
One of the great things about electronics is that it teaches you about all kinds
of things you can use in your life. For example, you discover
How electricity works and how to stay safe when working with it
How to read an electronic circuit and build it on a breadboard like the
one shown in Figure 1-2
How to use a variety of tools to solder, build, and customize casings to
hold your gadgets
How to work with integrated circuits
A bit about wiring (which can give you a head start when you decide to
learn how to add an outlet to your kitchen someday)
12 Part I: Project Prep
This book is full of lots of School of Hard Knocks information that might take
you years to acquire doing electronics projects on your own; you’ll also pick up
lots of wisdom as you work through the projects and try things out for yourself.
What You Need to Get Started
Now that you’re all excited about the benefits of working on electronics
projects, you’re probably wondering what this will cost you in dollars and
workspace.
How much will it cost?
We tried to keep the cost of the projects in this book to under $100; in many
cases, the materials and parts will cost you under $50 or so.
Depending on what you have lying around the house already, you might not
have to invest in some of the basic tools, such as pliers or a screwdriver. You
will probably have to spend $50 or so for electronics-specific tools and materials
such as a soldering iron, solder, and a multimeter like the one shown in
Figure 1-3.
Figure 1-2:
Here’s
what the
breadboard
for Dance to
the Music in
Chapter 5
looks like.
Chapter 1: Exploring the World of Electronics Projects 13
If you want to get really fancy, you could spend a couple hundred dollars on
fancy testing equipment such an oscilloscope, but you don’t have to have
that equipment to get through these projects, by any means.
Of course, in the world outside this book, projects can cost you hundreds of
dollars. Like any hobby, you can spend a few bucks to dabble or mortgage
your house to get into it in a big way. To get your feet wet in electronics,
though, the investment is not that great.
Keep in mind that you can reuse some of the parts of one project (such as a
breadboard) in another and cut your electronics budget further.
See Chapter 3 for information about the parts and tools that we recommend
you get to build your basic electronics workshop.
Space . . . the final frontier
One thing you do need to leap into the world of electronics projects is space.
That doesn’t mean you have to take over your living room and build a fancy
workbench. In most cases, a corner of your garage or laundry room stocked
Figure 1-3:
A multimeter
is a
measuring
device that
you’ll use
often.
14 Part I: Project Prep
with a shelf where you can keep parts and a card table works just fine. We do
advise that you find a specific space for your projects.
In short order, your workspace will be filled with tools and parts and all kinds
of (useful) junk (see Figure 1-4). See Chapter 2 for advice about safety when
working with all this stuff. For example, stock your workspace with safety
glasses that protect you whenever bits of wire go flying, and find a place where
you can keep your soldering iron in a stand so it doesn’t roll into your lap.
We also recommend finding a spot that you can close off if there are others
in your household — especially small children or pets — who could topple
your work surface or eat tiny electrical parts and do themselves damage.
Electronic projects don’t happen in a day, and you might work on a single
project over a matter of weeks. If you have a small room with a door to keep
others out, great. If not, use your common sense about what you leave out on
your work surface overnight.
Figure 1-4:
A typical
assortment
of electronics
paraphernalia.
Chapter 1: Exploring the World of Electronics Projects 15
16 Part I: Project Prep
Chapter 2
Safety First
In This Chapter
Avoiding those nasty shocks
Keeping your electric components safe from static discharge
Working safely with tools
Keeping yourself and your workspace neat and tidy (and safe)
We won’t kid you: Electricity deserves your respect. It can shock you,
burn you, and even kill you. In this book, we stick with projects that
work with AA batteries to limit the potential for serious damage.
Still, anytime you work with electronics, there is potential for danger. If these
projects get you excited about electronics so that you move on to projects
that use bigger jolts of electricity, now is the time to learn the proper respect
for electricity and the proper safety precautions when working with electronics
projects.
In this chapter, you discover what electricity is capable of — and how to keep
yourself, electrical components, tools, and those near and dear to you safe.
This is the one must-read chapter in this book. Humor us, and read it from
top to bottom, okay?
Avoiding Shocks Like the Plague
Your body is a delicate machine. Electric shocks, depending on certain conditions,
can be fatal, even at relatively low voltages. What comes out of your
wall outlet is deadly if you play around with it. Even electrical gadgets working
off batteries can cause you serious damage.
How voltage and current can get you
Your body is like a big resistor. Usually, your body’s resistance is high enough
to prevent damage when you’re exposed to low voltages. However, certain
conditions can lower your body’s resistance, lowering the amount of voltage
needed to cause you serious damage, such as giving you a nasty burn. Those
conditions might include handling electronics with sweaty palms or trying to
change your 12 volt (V) car battery on a rainy day — either can turn a slight
tingle into a fatal event.
Both AC (alternating current, such as the power from your wall outlet) and
DC (direct current, such as from a battery) voltage can damage you in different
ways:
AC voltage: This type of voltage regularly reverses direction. This can
cause your heart to shift its regular beating pattern in a condition known
as ventricular fibrillation. If this happens, your heart muscles go out of
whack in a way that causes blood to stop pumping. In this situation,
even if you cut the current, your heart might not be able to find its
proper rhythm, and you could die.
DC voltage: This type of voltage is on constantly and causes your muscles
to contract and seize up quickly (including your heart muscle). If
you grab an electrical device in conditions that cause your body to conduct
DC voltage, your hands could become frozen (unable to let go of the
device), and your heart could stop. If someone cuts the current quickly,
though, your heart might begin to beat again (and you’ll be able to
attend that Rotary luncheon next week).
Short of killing you, electric shock can cause burns as the current dissipates
across your body’s natural resistance (that is, your skin).
How much is too much?
Most resistance in your body is in your skin. If your skin is wet or damp, that
resistance is lowered. If you handle an electrical device with damp hands,
even voltages under 20V or so (not enough to even light a low-wattage lamp)
might be sufficient to do you serious damage. The 120V coming out of your
electrical outlet has a lot of punch: more than enough to kill you.
Four AA batteries in series — which is what we use in the projects in this
book — generate only about 6V. We did that on purpose to keep you relatively
safe.