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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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118 Part II: Aisle 5, Component Shack: Stocking Up_
In Chapter 1, we cover the units Hz and kHz in more detail.
Figure 5-10:
Noisy little buzzers.
Admit it — buzzers are cool. They can do everything from alerting you when somebody’s coming into your room to scaring the cat off the couch.
How buzzers Work
Here’s how a common type of buzzer works: Voltage applied to a piezoelectric crystal causes the crystal to expand or contract. If you attach a diaphragm to the crystal, changing voltage causes the diaphragm to vibrate and generate sound waves. You call these buzzers piezo buzzers, referring to the piezoelectric effect, the ability of certain crystals — quartz and topaz to name a few — to expand or contract when you apply voltage to them.
Some buzzers use electromagnets. For beginners, we recommend the piezo buzzer just to minimize the number of moving parts.
Buzzers have two leads and come in a variety of looks. Figure 5-10 shows a couple of typical buzzers. To connect the leads the correct way, remember that the red lead goes to positive DC voltage.
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Chapter 5: Filling Out Your Parts Bin 119
How noisy should your buzzer get?
A buzzer generates sound at one frequency; the specifications for a buzzer indicate several things:
The frequency of sound it emits: Most buzzers give off sound between 2kHz and 4kHz because humans can hear sound in that range very easily.
The operating voltage and voltage range: Just make sure that you get a buzzer that works with the DC voltage that your project supplies.
The level of sound it produces in units of decibels (db): A higher number of db indicates a louder sound. Higher DC voltage (within the voltage operating range of the buzzer) provides higher sound levels.
Be careful that the sound doesn’t get so loud that it damages your hearing. You can start to get an annoying ringing in your ears at levels of around 85 db and above.
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120 Part II: Aisle 5, Component Shack: Stocking Up
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Part III
Putting It on Paper
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In this part . . .
¦X ou find your way around the forest of electronics circuits with a schematic diagram, your road map to the components you need and how they connect to each other. In this part, you discover how to read a schematic and how to use a basic schematic to deduce whether a circuit beeps, lights up, spins around, or whatever. After you’re done, you’ll be able to make sense of what all those squiggly lines actually mean.
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Chapter 6
Reading a Schematic
In This Chapter
Understanding the role of schematics ^ Getting to know the most common symbols ^ Using (and not abusing!) component polarity ^ Diving into some specialized components ^ Having fun with schematics from around the world
magine driving cross-country without a roadmap. Chances are, you’d get lost along the way and end up driving in circles. Roadmaps exist to help you find your way. You can use roadmaps for building electronic circuits, as well. They’re called schematic diagrams, and they show you how all the parts of the circuits are connected. Schematics show these connections with symbols that represent electronic parts and lines that show how you attach the parts.
Although not all electronic circuits that you encounter are described in the form of a schematic, many are. If you’re serious at all about studying electronics, sooner or later, you need to understand how to read a schematic. Surprise! The language of schematics isn’t all that hard. Most schematic diagrams use only a small handful of symbols for components, such as resistors, capacitors, and transistors.
In this chapter, we tell you all that you really need to know so that you can read almost any schematic diagram you come across.
If you know how to read a roadmap, you’re already well on your way to reading a schematic. Schematic diagrams are a lot like maps, where lines connect
What’s a Schematic, and Why Should I Care?
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124 Part III: Putting It On Paper
things. But where a roadmap uses lines to connect dots and stars that represent towns and cities, schematics use lines to connect symbols representing resistors, transistors, and other components that make up a circuit.
Schematics serve two main purposes:
^ Show you how to reproduce a circuit. By reading the symbols and following the interconnections, you can build the circuit shown in the schematic.
^ Give you an overview of a circuit so that you can better understand how it works. You may find this knowledge useful if, for example, you need to repair the circuit or replace a component.
Discovering how to read a schematic is a little like learning a foreign language. On the whole, you find that most schematics follow fairly standard conventions. However, just as you can speak many languages with different dialects, the language of schematics is far from universal. Schematics can vary depending on the age of the diagram, its country of origin, the whim of the circuit designer, and many other factors.
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