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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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For many projects that require a 9-volt supply, you actually do better using a battery holder with six smaller voltage AA batteries than a single 9-volt battery. Why? The AA batteries last longer than the single 9-volt battery. The amount of electric current that a battery can generate before it depletes the chemicals it contains varies. A battery holder with six AA batteries cumulatively contains more chemicals than a single 9-volt battery, and so the battery holder lasts longer. (This example assumes that both batteries use the same chemicals, which we discuss later, in the section ďSorting batteries by whatís insideĒ). When you use a battery it begins to wear out and the voltage drops; for example we checked a 9-volt battery that weíd used for a few days and found that it was only producing 7-volts.
Batteries that just keep on going
If you have a project that uses a lot of current, or you plan to run the gadget all the time, it can eat through non-rechargeable AA batteries like you go through popcorn at a movie theater. In that case, you can use
C or D size batteries: These batteries are bigger than AA batteries; remember, the bigger the battery, the longer it lasts.
Rechargeable batteries: Some batteries allow you to revitalize the chemicals that they use, bringing them back to something like their original charge. See the next section for more about rechargeable batteries.
Though some (fool) hardy souls do recharge non-rechargeable batteries, itís not a good idea. The batteries can rupture and leak acid, or worse (think exploding batteries ó not a pretty picture).
Sorting batteries by whatís inside
Batteries are classified by the chemicals they contain. Note that any of the various size batteries that we discuss in the previous sections can contain these chemicals, and the chemicals in a battery relate to whether that battery is rechargeable or non-rechargeable.
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102 Part II: Aisle 5, Component Shack: Stocking Up
If you buy rechargeable batteries make sure that the battery charger you use is designed for that type of rechargeable battery.
Some of the readily available battery types use the following chemicals:
Zinc-carbon: This type of battery falls at the low quality end of non-rechargeable batteries. Although they donít cost very much, you have to replace them frequently.
Alkaline: We suggest that you start with this type of battery for your projects. These batteries last about three times as long as zinc-carbon batteries. When you find yourself doing so many projects that you need to replace these batteries frequently, step up to rechargeable batteries.
Nickel-cadmium (Ni-Cad or NiCad): This is the most popular type of rechargeable battery. Though many manufacturers have eliminated the problem today, the big flaw with some nickel-cadmium batteries is something called the memory effect. With the memory effect, you need to fully discharge the battery before recharging it to insure that it recharges to full capacity. If you donít discharge it, it doesnít charge fully. Nickel-cadmium batteries generate about 1.2 volts.
Nickel-metal hydride (Ni-MH): This type of rechargeable battery generates about 1.2 volts. This battery doesnít suffer from the memory effect seen in nickel-cadmium batteries. If you decide to use rechargeable batteries, we suggest that you start with these. Buying a recharger and a supply of these batteries saves you a considerable amount of money over time.
Lithium: If youíre working on a project that requires a lightweight battery, consider lithium. This type of battery generates higher voltage than other types, at about 3 volts. Lithium also has a higher capacity than alkaline batteries. They cost more, and you canít recharge most batteries of this type. But for a project where you need to watch your weight (no, we donít mean dieting), such as when moving a small robot around the house, you may find them very useful.
Donít worry about whether to use lithium-polymer or lithium-ion batteries. Some battery experts speculate that the manufacturing process for lithium-polymer batteries may evolve to produce a better battery in the future. However, at this point in time, you canít really make a strong case for them having any advantages over the lithium-ion type. So just go with the battery that you can find most easily, or the one that costs less.
Turning on power with solar cells
In Chapter 4, we discuss light-emitting diodes that generate light when you apply an electric current to them. Conversely, if you shine light on diodes,
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Chapter 5: Filling Out Your Parts Bin
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they generate an electric current. A solar cell is just a large diode that generates current when exposed to a light source, such as the sun.
To power a project, you can buy panels of solar cells. You have to weigh the voltage and current requirements for your project against the size of the solar panel. For example, a panel measuring about 5 x 5 inches may be able to generate 100 milliamps at 5 volts in bright sunlight. If you need 10 amps, you can get it, but you may find the size of the panel problematic on a smaller or more portable project.
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