to be heard by a single listener wearing headphones. Other amplifiers are huge, as they need to boost the signal enough so that 80,000 people can hear, for example, a famous singer forget the words to “The Star Spangled Banner.”
Speakers, which convert electrical current into sound you can hear. Speakers may be huge, or they may be small enough to fit in your ear.
Making light
Another common use of electronics is to produce light. The simplest electronic light circuits are LEDs, which are the electronic equivalent of a light bulb.
Video electronic devices are designed to create not just simple points of light but complete images that you can look at. The most obvious examples are television sets, which can provide hours and hours of entertainment and ask for so little in return — just a few of your brain cells.
Some types of electronic devices work with light that you can’t see. The most common are TV remote controls, which send infrared light to your television set whenever you push a button. (That is, assuming you can find the remote control.) The electronics inside the remote control manipulate the infrared light in a way that sends information from the remote control to the TV, telling it to turn up the volume, change channels, or turn off the power. (You learn how to work with infrared devices in Book 4, Chapter 4.)
Transmitting to the world
Radio refers to the transmission of information without wires. Originally, radio was used as a wireless form of telegraph, broadcasting nothing more than audible clicks. Next, radio was used to transmit sound. In fact, to this day the term radio is usually associated with audio-only transmissions, either in the form of music or the ever-popular talk radio. However, the transmission of video information — in other words, television — is also a form of radio, as are wireless networking, cordless phones, and cellphones.
You learn much more about radio electronics in Book 4, Chapter 3.
Computing
One of the most important applications of electronics in the last 50 years has been the development of computer technology. In just a few short decades, computers have gone from simple calculating machines to machines that can beat humans at games we once thought humans were the masters of, such as chess, Jeopardy!, and Go.
Computers are the most advanced form of a whole field of electronics known as digital electronics, which is concerned with manipulating data in the binary language of zeros and ones. You learn plenty about digital electronics in Books 5 through 8.
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 top; it has a variety of common electronic components. The underbelly of the circuit card is shown on the bottom; it has the typical silver streaks of conductors that connect the components topside so that they can perform useful work.
FIGURE 1-3: A typical electronic circuit board.
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.
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 see Chapter 4 of this minibook before you begin disassembling anything!
Chapter 2
Understanding Electricity
IN THIS CHAPTER