IN THIS CHAPTER

Understanding electricity

Defining the difference between electrical and electronic circuits

Perusing the most common uses for electronics

Looking at a typical electronic circuit board

I thought it would be fun to start this book with a story, so please bear with me. In January of 1880, Thomas Edison filed a patent for a new type of device that created light by passing an electric current through a carbon-coated filament contained in a sealed glass tube. In other words, Edison invented the light bulb. (Students of history will tell you that Edison didn’t really invent the light bulb; he just improved on previous ideas. But that’s not the point of the story.)

Edison’s light bulb patent was approved, but he still had a lot of work to do before he could begin manufacturing a commercially viable light bulb. The biggest problem with his design was that the lamps dimmed the more you used them. This was because when the carbon-coated filament inside the bulb got hot, it shed little particles of carbon, which stuck to the inside of the glass. These particles resulted in a black coating on the inside of the bulb, which obstructed the light.

Edison and his team of engineers tried desperately to discover a way to prevent this shedding of carbon. One day, someone on his team noticed that the black carbon came off of just one end of the filament, not both ends. The team thought that maybe some type of electric charge was coming out of the filament. To test this theory, they introduced a third wire into the lamp to see if it could catch some of this electric charge.

It did. They soon discovered that an electric current flowed from the heated filament to this third wire, and that the hotter the filament got, the more electric current flowed. This discovery, which came to be known as the Edison Effect, marks the beginning of technology known as electronics. The device, which Edison patented on November 15, 1883, is the world’s first electronic device.

When Edison patented his device in 1883, he had no idea what it would lead to. Now, just about 130 years later, it’s hard to imagine a world without electronics. Electronic devices are everywhere. There are more television sets in the United States than there are people. No one uses film to take pictures anymore; cameras have become electronic devices. And you rarely see a teenager anymore without headphones in his ears.

Without electronics, life would be very different.

Have you ever wondered what makes these electronic devices tick? In this chapter, I lay some important groundwork that will help the rest of this book make sense. I examine the bits and pieces that make up the most common types of electronic devices, and take a look at the basic concept that underlies all of electronics: electricity.

I promise I won’t bore you too much with tedious or complicated physics concepts, but I must warn you from the start: In order to learn how electronics works at a level that will let you begin to design and build your own electronic devices, you need to have at least a basic idea of what electricity is. Not just what it does, but what it actually is. So put on your thinking cap and get started.

What Is Electricity?

Before you can understand even the simplest concepts of electronics, you must first understand what electricity is. After all, the whole purpose of electronics is to get electricity to do useful and interesting things.

The concept of electricity is both familiar and mysterious. We all know what electricity is, or at least have a rough idea, based on practical experience. In particular, consider these points:

• We are very familiar with the electricity that flows through wires like water flows through a pipe. That electricity comes from power plants that burn coal, catch the wind, or harness nuclear reactions. It travels from the power plants to our houses in big cables hung high in the air or buried in the ground. Once it gets to our houses, it travels through wires through the walls until it gets to electrical outlets. From there, we plug in power cords to get the electricity into the electrical devices we depend on every day, such as ovens and toasters and vacuum cleaners.
• We know, because the electric company bills us for it every month, that electricity isn’t free. If we don’t pay the bill, the electric company turns off our electricity. Thus, we know that electricity is valuable.
• We know that electricity can be stored in batteries, which contain a limited amount of electricity that can be used up. When the batteries die, all their electricity is gone.
• We know that some kinds of batteries, like the ones in our cellphones, are rechargeable, which means that when they’ve been drained of all their electricity, more electricity can be put back into them by plugging them into a charger, which transfers electricity from an electrical outlet into the battery. Rechargeable batteries can be filled and drained over and over again, but eventually they lose their ability to be recharged — and you have to replace them with new batteries.
• We also know that electricity is the stuff that makes lightning strike in a thunderstorm. In grade school, we were taught that Ben Franklin discovered this by conducting an experiment involving a kite and a key, which we should not attempt to repeat at home.
• We know that electricity can be measured in volts. Household electricity is 120 volts (abbreviated 120 V). Flashlight batteries are 1.5 volts. Car batteries are 12 volts.
• We also know that electricity can be measured in watts. Traditional incandescent light bulbs are typically 60, 75, or 100 watts (abbreviated 100 W). Modern compact fluorescent lights (CFLs) have somewhat smaller wattage ratings. Microwave ovens and hair dryers are 1,000 or 1,200 watts. The more watts, the brighter the light or the faster your pizza reheats and your hair dries.
• We also may know that there’s a third way to measure electricity, called amps. A typical household electrical outlet is 15 amps (abbreviated 15 A).
• The truth is, most of us don’t really know the difference between volts, watts, and amps. (Don’t worry; by the time you finish Chapter 2 of this minibook, you will!)
• We know that there’s a special kind of electricity called static electricity that just sort of hangs around in the air, but that can be transferred to us by dragging our feet on a carpet, rubbing a balloon against our hairy arms, or forgetting to put an antistatic sheet in the dryer.

• And finally, we know that electricity can be very dangerous. In fact, dangerous enough that for almost 100 years electricity was used to administer the death penalty. Every year, hundreds of people die in the United States from accidental electrocutions.

But Really, What Is Electricity?

In the previous section, I list several ideas most of us have about electricity based on everyday experience. But the reality of electricity is something very different. Chapter 2 of this minibook is devoted to a deeper look at the nature of electricity, but for the purposes of this chapter, I want to start by introducing you to three very basic concepts of electricity: namely, electric charge, electric current, and electric circuit.

• Electric charge refers to a fundamental property of matter that even physicists as smart as Stephen Hawking don’t totally understand. Suffice it to say that two of the tiny particles that make up atoms — protons and electrons — are the bearers of electric charge. There are two types of charge: positive and negative. Protons have positive charge, electrons have negative charge.

  Electric charge is one of the basic forces of nature that hold the universe together. Positive and negative charges are irresistibly attracted to each other. Thus, the attraction of negatively charged electrons to positively charged protons hold atoms together.

  If an atom has the same number of protons as it has electrons, the positive charge of the protons balances out the negative charge of the electrons, and the atom itself has no overall charge.

  However, if an atom loses one of its electrons, the atom will have an extra proton, which gives the atom a net positive charge. When an atom has a net positive charge, it goes looking for an electron to restore its balanced charge.

  Similarly, if an atom somehow picks up an extra electron, the atom has a net negative charge. When this happens, the atom goes looking for a way to get rid of the extra electron to once again restore balance.

  Okay, technically atoms don’t really go “looking” for anything. They don’t have eyes, and they don’t have minds that are troubled when they’re short an electron or have a few too many. However, the natural attraction of negative to positive charges causes atoms that are short an electron to be attracted to atoms that are long an electron. When they find each other, something almost magic happens … The atom with the extra electron gives its electron to the atom that’s missing an electron. Thus, the charge represented by the electron moves from one atom to another, which brings us to the second important concept …

• Electric current refers to the flow of the electric charge carried by electrons as they jump from atom to atom. Electric current is a very familiar concept: When you turn on a light switch, electric current flows from the switch through the wire to the light, and the room is instantly illuminated.

  Electric current flows more easily in some types of atoms than in others. Atoms that let current flow easily are called conductors, whereas atoms that don’t let current flow easily are called insulators.

  Electrical wires are made of both conductors and insulators, as illustrated in Figure 1-1. Inside the wire is a conductor, such as copper or aluminum. The conductor provides a channel for the electric current to flow through. Surrounding the conductor is an outer layer of insulator, such as plastic or rubber.

  The insulator serves two purposes. First, it prevents you from touching the wire when current is flowing, thus preventing you from being the recipient of a nasty shock. But just as importantly, the insulator prevents the conductor inside the wire from touching the conductor inside a nearby wire. If the conductors were allowed to touch, the result would be a short circuit, which brings us to the third important concept …

• An electric circuit is a closed loop made of conductors and other electrical elements through which electric current can flow. For example, Figure 1-2 shows a very simple electrical circuit that consists of three elements: a battery, a lamp, and an electrical wire that connects the two.

  The circuit shown in Figure 1-2 is, as I already said, very simple. Circuits can get much more complex, consisting of dozens, hundreds, or even thousands or millions of separate components, all connected with conductors in precisely orchestrated ways so that each component can do its bit to contribute to the overall purpose of the circuit. But all circuits must obey the basic principle of a closed loop.

  All circuits must create a closed loop that provides a complete path from the source of voltage (in this case, the battery) through the various components that make up the circuit (in this case, the lamp) and back to the source (again, the battery).

What Is Electronics?

One of the reasons I started this chapter with the history lesson about Thomas Edison was to point out that when the whole field of electronics was invented in 1883, electrical devices had already been around for at least 100 years. For example:

• Benjamin Franklin was flying kites in thunderstorms more than 100 years before.
• The first electric batteries were invented by a fellow named Alessandro Volta in 1800. Volta’s contribution is so important that the common term volt is named for him. (There is some archeological evidence that the ancient Parthian Empire may have invented the electric battery in the second century BC, but if so we don’t know what they used their batteries for, and their invention was forgotten for 2,000 years.)
• The electric telegraph was invented in the 1830s and popularized in America by Samuel Morse, who invented the famous Morse code used to encode the alphabet and numerals into a series of short and long clicks that could be transmitted via telegraph. In 1866, a telegraph cable was laid across the Atlantic Ocean, allowing instantaneous communication between the United States and Europe.
• Contrary to popular belief, Benjamin Franklin wasn’t the first to fly a kite in a thunderstorm. In 1850, he published a paper outlining his idea. Then he let a few other people try it first. After they survived, he tried the experiment himself and wound up getting all the credit. Benjamin Franklin was not only very smart; he was also very wise.

All of these devices, and many other common devices still in use today, such as light bulbs, vacuum cleaners, and toasters, are known as electrical devices. So what exactly is the difference between electrical devices and electronic devices?

The answer lies in how devices manipulate electricity to do their work. Electrical devices take the energy of electric current and transform it in simple ways into some other form of energy — most likely light, heat, or motion. For example, light bulbs turn electrical energy into light so you can stay up late at night reading this book. The heating elements in a toaster turn electrical energy into heat so you can burn your toast. And the motor in your vacuum cleaner turns electrical energy into motion that drives a pump that sucks the burnt toast crumbs out of your carpet.

In contrast, electronic devices do much more. Instead of just converting electrical energy into heat, light, or motion, electronic devices are designed to manipulate the electrical current itself to coax it into doing interesting and useful things.

That very first electronic device invented in 1883 by Thomas Edison manipulated the electric current passing through a light bulb in a way that let Edison create a device that could monitor the voltage being provided to an electrical circuit and automatically increase or decrease the voltage if it became too low or too high.

Don’t worry if you aren’t certain what the term voltage means at this point. You learn about voltage in the next chapter.

One of the most common things that electronic devices do is manipulate electric current in a way that adds meaningful information to the current. For example, audio electronic devices add sound information to an electric current so that you can listen to music or talk on a cellphone. And video devices add images to an electric current so you can watch great movies like Office Space, Ferris Bueller’s Day Off, or The Princess Bride over and over again until you know every line by heart.

Keep in mind that the distinction between electric and electronic devices is a bit blurry. What used to be simple electrical devices now often include some electronic components in them. For example, your toaster may contain an electronic thermostat that attempts to keep the heat at just the right temperature to make perfect toast. (It will probably still burn your toast, but at least it tries not to.) And even the most complicated electronic devices have simple electrical components in them. For example, although your TV set’s remote control is a pretty complicated little electronic device, it contains batteries, which are simple electrical devices.

What Can You Do with Electronics?

The amazing thing about electronics is that it’s being used today to do things that weren’t even imaginable just a few years ago. And of course, that means that in just a few years we’ll have electronic devices that haven’t even been thought up yet.

That being said, the following sections give a very brief overview of some of the basic things you can do with electronics.

Looking inside Electronic Devices

Have you ever taken apart an electronic device that no longer works, like an old clock radio or VHS tape player, just to see what it looks like on the inside?

I just took some hefty server computers to an e-waste recycler. You can bet that before I did, I opened them up to see what they looked like on the inside. And I removed a couple of the more interesting pieces to keep on my shelf. (Call me weird if you want. Some people collect teacups, some people collect spoons from around the world, and some people collect shot glasses. I collect old computer CPUs.)

Inside most electronic devices, you’ll find a circuit board (or circuit card; it’s all the same), which is a flat, thin board that has electronic gizmos mounted on it. In most cases, one side of the circuit board is populated with tiny devices that look like little buildings. These are the components that make up the electric circuit: the resistors, capacitors, diodes, transistors, and integrated circuits that do the work that the circuit is destined to do. The other side is painted with little lines of silver or copper that look like streets. These are the conductors that connect all the components so that they can work together.

An electronic circuit board looks like a little city! For example, have a look at the typical circuit board pictured in Figure 1-3. The top of the card is shown on the left; it has a variety of common electronic components. The underbelly of the circuit card is shown on the right; it has the typical silver streaks of conductors that connect the components topside so that they can perform useful work.

Here’s the essence of what’s going on with these two sides of the circuit card:

• The component side of the card — the side with the little buildings — holds a collection of electronic components whose sole purpose in life is to bend, turn, and twist electric current to get it to do interesting and useful things. Some of those components restrict the flow of current, like speed bumps on a road. Others make the current stronger. Some work like One-Way street signs that allow current to flow in only one direction. Still others try to smooth out any ripples or variations in the current, resulting in smoother traffic flow.
• The circuit side of the card — the side with the roads — provides the conductive pathways for the electric current to flow from one component to the other in a certain order. The whole trick of designing and building electronic circuits is to connect all the components together in just the right way so that the current that flows out of one component is passed on to the next component. The circuit side of the board is what lets the components work together in a coordinated way.

Okay, I couldn’t even get through the first chapter of this book without having to give you the first of many warnings about the dangers of working with electronics. So here it goes: Do not under any circumstances plunge carelessly into the disassembly of old electronic circuits until you’re certain you know what you’re doing.

The little components on a circuit card such as the one shown in Figure 1-3 can be dangerous, even when they are unplugged. In fact, the two tall cylindrical components near the back edge of this circuit card are called capacitors. They can contain stored electrical energy that can deliver a powerful — even fatal — shock long after you’ve unplugged the power cord. Please refer to Chapter 4 of this minibook before you begin disassembling anything!