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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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Table 6-3 shows several common schematic symbols for light-sensitive components: Photocells/photoresistors, photodiodes, phototransistors, and solar cells.
Table 6-3 Photo Sensitive Component Symbols
Name Symbol Function
Photocell/Photoresistor* Light-sensitive version of a resistor
Photodiode & Light-sensitive version of a diode
Phototransistor Light-sensitive version of a transistor
Solar cell % Generates electricity in response to sunlight
* Note that you can use the terms photocell and photoresistor interchangeably.
Alternative Schematic Drawing Styles
The schematic symbols in this chapter belong to the drawing style used in North America (particularly in the United States) and in Japan. In some countries, notably European nations as well as Australia, somewhat different schematic symbols are used. If youíre using a schematic for a circuit not designed in the United States or Japan, you need to do a wee bit oí schematic translation in order to understand all the components.
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140 Part III: Putting It On Paper
Figure 6-9 shows a sampling of schematic symbols commonly used in the United Kingdom and Europe. Notice that there are some obvious differences in the resistor symbols, both fixed and variable.
-CZb
RESISTOR
VARIABLE
RESISTOR
Figure 6-9:
Schematic symbols used for circuits designed in Europe and the United Kingdom.
CAPACI TOR
1
GROUND
VAR ABLE CAPACI TOR
T
POS T VE VOLTAGE
This style organizes its symbols differently than the American style. In the United States, you express resistor values over 1,000 ohms in the form of 6.8K or 10.2K, with the K following the value. The European schematic style eliminates the decimal point. Typical of schematics youíd find in the United Kingdom are resistor values expressed in the form of 6K8 or 10K2. This style substitutes the K (which stands for kilohms, or thousands of ohms) for the decimal point.
You may encounter a few other variations in schematic drawing styles, but all are fairly self-explanatory and the differences are not substantial. After you learn how to use one style of drawing, the others come easily.
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Chapter 7
Understanding the Basics of Electronics Circuits
In This Chapter
^ Seeing a circuit for what it is ^ Looking at a basic circuit ^ Arranging circuits in series and parallel ^ Lowering your voltage with a voltage divider circuit ^ Taking the measure of current ^ Teaming up resistors and capacitors ^ Working with transistors ^ Amplifying even better with an op amp ^ Keeping things simple with ICs
f
ˇ magine that youíre building a cute little cottage rather than an electronic gadget. You have to know about the tools and materials that you need to build the thing, and you need to gain skills, such as carpentry and plumbing. But before you begin sawing and plumbing, you have to have a blueprint that gives you an idea of what the final product should look like. Thatís what a schematic is: A blueprint of an electronic circuit that forms the basis of your electronic gadget.
This chapter covers the basics of electronic circuits and examines the basic building blocks that let you trace through the schematic for any project and understand how a circuit functions. Thereís one prerequisite with this chapter: itís really important that you read Chapter 6 before you read this one so you donít get lost.
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142 Part III: Putting It On Paper_
What the Heck Is a Circuit?
An electronic circuit is simply a collection of components connected together with wires through which an electric current moves. You can think of a circuit as composed of five parts:
^ A power source
^ Components, such as resistors and transistors ^ Wires to connect everything together
^ An output device (also referred to as the load), such as a speaker ^ Ground to complete the circuit ^ Many, but not all circuits, also have an input
A Very Basic Circuit
You donít want to start building houses by tackling a 36-room mansion with a complex home stereo system wired into the walls and a maze-like set of secret passages in the basement, right? You also shouldnít start your exploration of electronic circuits with anything overwhelming. So we start you off with the equivalent of building a shed: A simple circuit that powers a light bulb.
Powering a light bulb
One of the simplest circuits that you encounter involves a light bulb and two wires that connect the bulb to a power source. However, you may not find this circuit very practical because the light bulb is always on. Adding a switch to turn the light on or off makes the circuit much more useful. Figure 7-1 shows the schematic of a circuit that contains a light bulb and switch.
Figure 7-1:
This circuit powers a light to chase away the dark.
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Chapter 7: Understanding the Basics of Electronics Circuits 143
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