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Electronics for dummies - McComb G.

McComb G., Boes E. Electronics for dummies - Wiley publishing, 2005. - 433 p.
ISBN: 0-7645-7660-7
Download (direct link): electronicsfordummies2005.pdf
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^ Plugs and jacks that carry audio signals between equipment, as from a guitar to an amplifier, have cables such as the one you see in Figure 5-2. There are plugs on both ends of the cable and a jack is mounted on both the guitar and amplifier. These cables contain either one or two signal wires; a metal shield surrounds the wires. This metal shield minimizes the introduction of current into the wires, limiting noise that can disrupt a signal.
You typically use pin headers to bring signals to and from circuit boards (we talk more about circuit boards in Chapter 12). You mount the socket half of this kind of connector on the circuit board, and you attach the plug half to a ribbon cable. The rectangular shape of the connector allows for easy routing of signals from each wire in the cable to the correct part of the circuit board. You refer to these connectors by the number of pins — for example, you may talk about a 40-pin header. After you start building robots or other more complex projects that involve more than one circuit board, you can find a use for this type of connector.
Electronics uses many connectors that you don’t need to know about until you get into more complex projects. When you build that spaceship, or any other more complicated gadget, you can look up details on the connectors that you need on many electronic suppliers’ Web sites or in catalogs.
Powering Up
All the wires and connectors in the world won’t do you much good if you don’t have a power source. After you build a project, you need voltage and current to get the thing going. You can get power from your wall outlet (we talk about plugging into your wall outlet in Chapter 3), batteries, or solar cells.
For electronics projects, batteries and solar cells make great power sources because they’re lightweight and portable. The following sections discuss how to choose batteries and solar cells for your projects.
Turning the juice on with batteries
A battery uses a process called an electrochemical reaction to produce a positive voltage at one terminal and a negative voltage at the other terminal. This process involves placing two different types of metal in a certain type of
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Chapter 5: Filling Out Your Parts Bin
chemical. (Because you didn’t buy Chemistry For Dummies — by John T. Moore from Wiley Publishing, by the way — we don’t get into the guts of a battery here, just the basics.)
You can categorize batteries by size, voltage, and the type of chemicals that they contain, such as zinc-carbon or nickel-cadmium. Figure 5-3 shows a few typical battery sizes.
Starting with your eVeryday-type batteries
Start with the standard, non-rechargeable type of batteries that you can buy in any supermarket. The AAA-, AA-, C-, and D-size batteries all produce about 1.5 volts, compared to the transistor battery (that little rectangular battery that looks sort of like a Lego® block found in lots of small electronic gadgets) that produces about 9 volts and the lantern battery (that big boxy thing that fits in flashlights the size of a boom box) that produces about 6 volts.
You can combine any number of 1.5-volt batteries to get the voltage that you need for your project. For example, when you connect the positive terminal of one battery to the negative terminal of another battery (you call this set-up connecting the batteries in series), as in Figure 5-4, you get twice the voltage.
Figure 5-3:
Getting alphabetical with batteries in small (AA), medium (C) and large sizes (D).
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100 Part II: Aisle 5, Component Shack: Stocking Up
NEGATIVE POSITIVE
TERMI NAL TERMI NAL
SINGLE BATTERY PRODUCES 1.5 VOLTS
Figure 5-4:
By
connecting two batteries like this you get twice
the voltage. TWO BATTERIES IN “SERIES”
PRODUCE 3 VOLTS
You put batteries together in battery holders. When you place four 1.5-volt batteries in a battery holder, for example, those batteries combine to produce 6 volts; when you place six 1.5-volt batteries in a battery holder, they combine to produce 9 volts; and so on. Figure 5-5 shows a battery holder containing four AA batteries.
Figure 5-5:
Four 1.5-volt batteries tucked into a battery holder produce about 6 volts.
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Chapter 5: Filling Out Your Parts Bin 101
Taking AA batteries to the max
The amp-hour or milliamp-hour rating for a battery gives you a measure of how much current a battery can conduct for a given length of time. For example, a 9-volt transistor battery usually has about a 500 milliamp-hour rating (this measurement varies with the battery type; see the section "Sorting batteries by what's inside" for
more about battery types). Such a battery can power a circuit using 25 milliamps for approximately 20 hours before its voltage begins to drop. An AA battery may have a 1500 milliamp-hour rating. Therefore, a battery pack containing AA batteries can power a circuit using 25 milliamps for approximately 60 hours.
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