Electronics For Dummies
Overview
Build your electronics workbench—and begin creating fun electronics projects right away
Packed with hundreds of diagrams and photographs, this book provides step-by-step instructions for experiments that show you how electronic components work, advice on choosing and using essential tools, and exciting projects you can build in 30 minutes or less. You'll get charged up as you transform theory into action in chapter after chapter!
- Circuit basics — learn what voltage is, where current flows (and doesn't flow), and how power is used in a circuit
- Critical components — discover how resistors, capacitors, inductors, diodes, and transistors control and shape electric current
- Versatile chips — find out how to use analog and digital integrated circuits to build complex projects with just a few parts
- Analyze circuits — understand the rules that govern current and voltage and learn how to apply them
- Safety tips — get a thorough grounding in how to protect yourself—and your electronics—from harm
P.S. If you think this book seems familiar, you’re probably right. The Dummies team updated the cover and design to give the book a fresh feel, but the content is the same as the previous release of Electronics For Dummies (9781119117971). The book you see here shouldn’t be considered a new or updated product. But if you’re in the mood to learn something new, check out some of our other books. We’re always writing about new topics!
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About The Author
Cathleen Shamieh is an electrical engineer and a technical writer with extensive engineering and consulting experience in the fields of medical electronics, speech processing, and telecommunications.
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electronics for dummies
CHEAT SHEET
Electronics is more than just schematics and circuits. By using various components, such as resistors and capacitors, electronics allows you to bend electric current to your will to create an infinite variety of gizmos and gadgets. In exploring electronics, use this handy reference for working with Ohm’s, Joule’s, and Kirchhoff’s Laws; making important calculations; determining the values of resistors and capacitors according to the codes that appear on their casings; and using a 555 timer and other integrated circuits (ICs).
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Looking for some great sources for your electronic parts? This list gives you some perennial favorites, both inside and outside North America. This list is by no means exhaustive; you can find literally thousands of specialty outlets for new and used electronics.
Plus, Amazon and eBay provide virtual marketplaces for all sorts of sellers — from established retailers to individuals selling parts and components out of their homes.
Ever wonder who invented the battery? Or how electrons, amps, volts, and ohms got their names? Curious to know who discovered that electricity and magnetism are related, and who came up with the idea for the electric motor? Has it ever occurred to you that the laws that govern voltage, current, and energy dissipation in a circuit didn’t just appear on two tablets, but were discovered after painstaking research and experimentation?
General Electronics
Ready to build on a newfound knowledge of electronics? Want to expand your horizons and create programmable electronics projects? The following list provides you with a list of ideas for enhancing your electronics experience.
Surfing for circuits
Thousands of project ideas are available on the Internet. Use your favorite search engine to find projects in topics or specific parts that interest you.
The diagram shown depicts a battery-operated circuit that powers a light-emitting diode (LED), much like what you might find in a mini LED flashlight. What you see in the figure is a circuit diagram, or schematic, that shows all the components of the circuit and how they are connected.
Current delivers electrical energy from the battery to the resistor and the LED.
One of the first transistors to be invented was the bipolar junction transistor (BJT), and BJTs are what most hobbyists use in home-brewed circuits. BJTs consist of two pn-junctions fused together to form a three-layer sandwich-like structure.
A pn-junction is the boundary between two different types of semiconductors: a P-type semiconductor, which contains positive charge carriers (known as holes), and an N-type semiconductor, which contains negative charge carriers (electrons).
General Electronics
Resistors come in two basic flavors: fixed and variable. Both types are commonly used in electronic circuits. Here's the lowdown on each type and why you would choose one or the other:
A fixed resistor supplies a constant, factory-determined resistance. You use it when you want to restrict current to within a certain range or divide voltage in a particular way.
You need a closed path, or closed circuit, to get electric current to flow. If there's a break anywhere in the path, you have an open circuit, and the current stops flowing — and the metal atoms in the wire quickly settle down to a peaceful, electrically neutral existence.
A closed circuit allows current to flow, but an open circuit leaves electrons stranded.
Early experimenters believed that electric current was the flow of positive charges, so they described electric current as the flow of a positive charge from a positive terminal to a negative terminal. Much later, experimenters discovered electrons and determined that they flow from a negative terminal to a positive terminal.
General Electronics
An oscilloscope lets you look at an electrical signal by displaying how a voltage varies with time as a trace across a display. The vertical axis voltage indicates the amount of voltage (also called amplitude), and the horizontal axis represents time. (Remember graphing equations in math class? Well, the display on a scope is really such a graph.
Electronics is more than just schematics and circuits. By using various components, such as resistors and capacitors, electronics allows you to bend electric current to your will to create an infinite variety of gizmos and gadgets. In exploring electronics, use this handy reference for working with Ohm’s, Joule’s, and Kirchhoff’s Laws; making important calculations; determining the values of resistors and capacitors according to the codes that appear on their casings; and using a 555 timer and other integrated circuits (ICs).
General Electronics
The 555 can behave as an astable multivibrator, or oscillator. By connecting components to the chip in your electronics, you can configure the 555 to produce a continuous series of voltage pulses that automatically alternate between low (0 volts) and high (the positive supply voltage, VCC).
You can calculate
Diodes and transistors are made from semiconductors such as silicon and germanium. Pure semiconductors won’t conduct electric current, but if you dope a semiconductor by adding certain types of impurities, known as dopants, you change the electrical characteristics of the semiconductor, and it will conduct when a voltage is applied to it in just the right way.
General Electronics
The pins on an IC chip provide connections to the tiny integrated circuits inside of your electronics. To determine which pin is which, you look down on the top of the IC for the clocking mark, which is usually a small notch in the packaging but might instead be a little dimple or a white or colored stripe. By convention, the pins on an IC are numbered counterclockwise, starting with the upper-left pin closest to the clocking mark.
General Electronics
Electronics can sometimes be difficult to decipher. By decoding the colorful stripes sported by many resistors and the alphanumeric markings that appear on certain types of capacitors, you can determine the nominal value and tolerance of the specific component.
Resistor color codes
Many resistor casings contain color bands that represent the nominal resistance value and tolerance of the resistor.
A field-effect transistor (FET) consists of a channel of N- or P-type semiconductor material through which current can flow, with a different material (laid across a section of the channel) controlling the conductivity of the channel.
In a field-effect transistor (FET), voltage applied to the gate controls the flow of current through a channel from the source to the drain.
The attractive rainbow colors adorning most fixed resistors serve a purpose beyond catching your eye. Color-coding identifies the nominal value and tolerance of most resistors; the others are drab and boring, and have their values stamped on them.
The color code starts near the edge of one side of the resistor and consists of several stripes, or bands, of color.
General Electronics
Switches in electronics are categorized by how many connections they make when you "flip the switch" and exactly how those connections are made. A switch can have one or more poles, or sets of input contacts: A single-pole switch has one input contact, whereas a double-pole switch has two input contacts.
A switch can also have one or more conducting positions, or throws.
Bipolar junction transistors (BJTs) and field-effect transistors (FETs) work basically the same way. The voltage you apply to the input (base, for a BJT, or gate, for a FET) determines whether or not current flows through the transistor (from collector to emitter for a BJT, and from source to drain for a FET).
Circuits are the building blocks of electronics projects. You need several parts in order to build a basic LED circuit. Here is a list of those parts:
Four 1.5-volt AA batteries (make sure they're fresh)
One four-battery holder (for AA batteries)
One battery clip
One 2.2
(identified by a red-red-red stripe pattern and then a gold or silver stripe)
One red LED (any size)
Three insulated alligator clips or one solderless breadboard
Insert the batteries into the battery holder, observing the polarity markers, and attach the battery clip.
General Electronics
When you have a good handle on Ohm's Law, you'll be ready to put it into practice. Ohm's Law is like a master key, unlocking the secrets to electronic circuits.
In the simple circuit shown here, a 9-volt battery is applied across a 1
You calculate the current through the resistor as follows:
If you add a 220 ohm resistor in series, as shown here, you're restricting the current even more.
The amount of energy consumed by an electronic component is known as power (abbreviated P), measured in watts (abbreviated W). Here is the equation for calculating power:
P = V x I
where V represents voltage and I represents current. When you know the voltage dropped across a component and the current passing through the component, you can use the power equation to calculate the amount of energy consumed by each component.
General Electronics
To figure out how much voltage is dropped across each resistor, you use Ohm's Law for each individual resistor. You know the value of each resistor, and you know the current flowing through each resistor. Remember that current (I) is the battery voltage (9 V) divided by the total resistance (R1 + R2), or approximately 7.
General Electronics
Switches in electronics are referred to by names that indicate how the switching action is controlled. You see some of the many different types of switches in this figure.
From top to bottom: two toggle switches, a rocker switch, and a leaf switch.
Chances are, you encounter one or more of the following types of switches as you go about your daily routine:
Slide switch: You slide a knob back and forth to open and close this type of switch, which you find on many flashlights.
Most electronic circuits are combinations of series and parallel connections. How you arrange components in a circuit depends on what you're trying to do. Take a look at the series-parallel circuit shown here.
By opening and closing switches in this series-parallel circuit, you can direct the supply current through different paths.
General Electronics
As you learn more about electronics, you may get curious enough to take a look inside some of the electronics in your house. Warning: Be careful! You might (for example) open up the remote control for your TV and see some components wired up between a touchpad and an LED.
On printed circuit boards (PCBs) — which serve as platforms for building the mass-produced circuits commonly found in computers and other electronic systems — you may have trouble recognizing the individual circuit components.
To measure the current running through your LED circuit, you must pass the current through your multimeter. The only way to do this is to interrupt the circuit between two components and insert your multimeter, as if it's a circuit component, to complete the circuit.
Switch the multimeter selector to measure DC current in milliamps (mA).
You can use your multimeter to measure the voltage across the battery pack, the resistor, and the LED in a circuit. Note that the connection points between components are the same whether you built the circuit using a breadboard or alligator clips.
The red lead of your multimeter should be at a higher voltage than the black lead, so take care to orient the probes as described.
General Electronics
The semiconductor material in a transistor is the size of a grain of sand or even smaller, so manufacturers put these teensy components in a metal or plastic case with leads sticking out so you can connect them in your circuits. You can find literally dozens upon dozens of different shapes and sizes of transistors, some of which are shown here.
General Electronics
Switching is far and away the most important function in electronics. Think about your TV set: You turn it on and off, select a signal source from several different input choices (such as your DVD player, cable box, or gaming system), and change TV channels.
Your TV screen consists of millions of tiny pixels (picture elements), each of which is, in essence, a red, blue, or green light that is either on or off.
General Electronics
You can set up a simple electronic circuit to connect and disconnect your battery pack from any circuits you build on a solderless breadboard without having to physically remove the battery pack from the breadboard.
In the following figure, the positive terminal of the battery is connected to the top terminal of an SPDT switch.
With just a handful of basic mathematical formulas, you can get pretty far in analyzing the goings-on in electronic circuits and in choosing values for electronic components in circuits you design.
Ohm’s Law and Joule’s Law
Ohm’s Law and Joule’s Law are commonly used in calculations dealing with electronic circuits.
Zener diodes are special diodes that are meant to break down. They are really just heavily doped diodes that break down at much lower voltages than standard diodes. When you reverse-bias a Zener diode, and the voltage across it reaches or exceeds its breakdown voltage, the Zener diode suddenly starts conducting current backward through the diode (from cathode to anode).
General Electronics
Surplus is a loaded word, especially when shopping for electronics. To some, it means junk that just fills up the garage, like musty canvas tents or funky fold-up shovels that the US Army used back in the 1950s. To the true electronics buff, surplus has a different meaning: affordable components that help stretch the electronics-building dollar.
A scientist hard at work in the early 1800s was the energetic James Prescott Joule. Joule is responsible for coming up with the equation that gives you power values; it's known as Joule's Law:
P = V x I
This equation states that the power (in watts) equals the voltage (in volts) across a component times the current (in amps) passing through that component.
Atoms are the basic building blocks of everything in the universe, whether natural or manmade. They’re so tiny that you’d find millions of them in a single speck of dust. Electric current, sometimes known as electricity, is the movement in the same direction of microscopically small, electrically charged particles called electrons.
Electric charge is a property of certain particles, such as electrons, protons, and quarks (yes, quarks) that describes how they interact with each other. There are two different types of electric charge, somewhat arbitrarily named positive and negative (much like the four cardinal directions are named north, south, east, and west).
To complete many experiments and projects, you'll need a few tools that may cost you $100 to $250 total, depending on where you shop. Besides the essential listed here, you'll need to have a calculator handy.A multimeter and spring-loaded test clips.The multimeter enables you to measure voltage, resistance, and current, and is essential for understanding what’s going on (or not) in the circuits you build.
Transistors are commonly used to amplify signals. An electrical signal is the pattern over time of an electrical current. Often, the way an electrical signal changes its shape conveys information about something physical, such as the intensity of light, heat, or sound, or the position of an object, such as the diaphragm in a microphone or the shaft of a motor.
General Electronics
Transistors basically do just two things in electronic circuits: switch and amplify. But those two jobs are the key to getting really interesting things done. Here's why those functions are so important:
Switching: If you can switch electron flow on and off, you have control over the flow, and you can build involved circuits by incorporating lots of switches in the right places.
General Electronics
Electric current doesn’t flow just anywhere. (If it did, you’d be getting shocked all the time.) Electrons flow only if you provide a closed conductive path, known as an electrical circuit, or simply a circuit, for them to move through, and initiate the flow with a battery or other source of electrical energy.
Potentiometers, or pots, allow you to adjust resistance continuously. Pots are three-terminal devices, meaning that they provide three places to connect to the outside world. Between the two outermost terminals is a fixed resistance — the maximum value of the pot.
Between the center terminal and either end terminal is an amount of resistance that varies depending on the position of a rotatable shaft or other control mechanism on the outside of the pot.
If you hear the word "ground" used in an electronics context, be aware that ground can refer to either earth ground or common ground. Earth ground means pretty much what it says: It's a direct connection to the ground — real ground, the stuff of the planet.
The screw in the center of a standard two-prong AC outlet, as well as the third prong in a three-prong outlet, is connected to earth ground.
Resistors are among the most popular electronic components around because they're simple yet versatile. One of the most common uses of a resistor is to limit the amount of current in part of a circuit. However, resistors can also be used to control the amount of voltage provided to part of a circuit and to help create timing circuits.
Circuits in electronics usually don't look as neat and geometric as you might expect. The shape of a circuit is usually not important for its operation. What matters about any circuit — and what you should concern yourself with when building one — is how the components are connected, because the connections show you the path the current takes through the circuit.
The term electricity is ambiguous, often contradictory, and can lead to confusion, even among scientists and teachers. Generally speaking, electricity has to do with how certain types of particles in nature interact with each other when in close proximity.
Rather than rely on the term electricity as you explore the field of electronics, you’re better off using other, more precise, terminology to describe all things electric.
Electrical systems use electric current to power things such as light bulbs and kitchen appliances. Electronic systems take this a step further. When you turn on a light in your home, you’re connecting a source of electrical energy (usually supplied by your power company) to a light bulb in a complete path, known as an electrical circuit.
The word potentiometer is often used to categorize all variable resistors, but another type of variable resistor, known as a rheostat, is different from a true potentiometer. Rheostats are two-terminal devices, with one lead connected to the wiper and the other lead connected to one end of the resistance track.
General Electronics
When you're shopping around for electronics parts, you may see the term RoHS compliant next to some of the parts. The term RoHS (pronounced "ROW-haas") refers to the Restriction of Hazardous Substances directive adopted in 2003 by the European Union (E.U.).
The RoHS directive, which took effect in 2006, restricts the placement on the E.
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