Electronics For Dummies book cover

Electronics For Dummies

By: Cathleen Shamieh Published: 12-05-2019

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!

Articles From Electronics For Dummies

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48 results
48 results
Electronics For Dummies Cheat Sheet

Cheat Sheet / Updated 12-15-2021

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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Closed, Open, and Short Circuits

Article / Updated 09-17-2021

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. Picture a gallon of water flowing through an open pipe. The water will flow for a short time but then stop when all the water exits the pipe. If you pump water through a closed pipe system, the water will continue to flow as long as you keep forcing it to move. Open circuits by design Open circuits are often created by design. For instance, a simple light switch opens and closes the circuit that connects a light to a power source. When you build a circuit, it's a good idea to disconnect the battery or other power source when the circuit is not in use. Technically, that's creating an open circuit. A flashlight that is off is an open circuit. In the flashlight shown here, the flat black button in the lower left controls the switch inside. The switch is nothing more than two flexible pieces of metal in close proximity to each other. With the black button slid all the way to the right, the switch is in an open position and the flashlight is off. A switch in the open position disconnects the light bulb from the battery, creating an open circuit. Turning the flashlight on by sliding the black button to the left pushes the two pieces of metal together — or closes the switch — and completes the circuit so that current can flow. Closing the switch completes the conductive path in this flashlight, allowing electrons to flow. Open circuits by accident Sometimes open circuits are created by accident. You forget to connect a battery, for instance, or there's a break in a wire somewhere in your circuit. When you build a circuit using a solderless breadboard, you may mistakenly plug one side of a component into the wrong hole in the breadboard, leaving that component unconnected and creating an open circuit. Accidental open circuits are usually harmless but can be the source of much frustration when you're trying to figure out why your circuit isn't working the way you think it should. Short circuits take the wrong path Short circuits are another matter entirely. A short circuit is a direct connection between two points in a circuit that aren't supposed to be directly connected, such as the two terminals of a power supply. Electric current takes the path of least resistance, so in a short circuit, the current will bypass other parallel paths and travel through the direct connection. (Think of the current as being lazy and taking the path through which it doesn't have to do much work.) In a short circuit, current may be diverted from the path you intended it to flow through. If you short out a power supply, you send large amounts of electrical energy from one side of the power supply to the other. With nothing in the circuit to limit the current and absorb the electrical energy, heat builds up quickly in the wire and in the power supply. A short circuit can melt the insulation around a wire and may cause a fire, an explosion, or a release of harmful chemicals from certain power supplies, such as a rechargeable battery or a car battery.

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Tools Needed for Electronics Projects

Step by Step / Updated 03-27-2016

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.

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Displaying Electrical Signals on an Oscilloscope

Article / Updated 03-26-2016

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.) Oscilloscopes always sweep left to right, so you read the timeline of the signal from left to right, just as you’d read a line of English on a page. The signal that you observe on the oscilloscope is a waveform. Some waveforms are simple, some are complex. The four most common waveforms that you encounter in electronics are DC (direct current) waveform: A flat, straight line. AC (alternating current) waveform: This waveform undulates over time. The most common AC waveform is a sine wave, but you may also encounter triangle waves, sawtooth waves, and other AC waveform shapes. Digital waveform: A DC signal that alternates between low (usually 0 V), which indicates logical 0, and high (usually 5 V), which indicates logical 1. Pulse waveform: A signal that changes abruptly between low and high states. Most pulse waveforms are digital and usually serve as a timing mark, like the starter’s gun at a race. An oscilloscope display has a built-in grid to help you measure time along the X (horizontal) axis and voltage along the Y (vertical) axis. Using knobs on the front panel, you select the voltage scale (for instance, 5 V/division) and sweep time (for instance, 10 ms/division) of the display. As you adjust these settings, you see the voltage display change proportionally. You can read a voltage level at a particular time by determining the position of the voltage on the grid and multiplying that by the voltage scale you’ve selected. A DC waveform’s vertical position (amplitude) gives you the DC voltage reading. For AC signals, the oscilloscope display enables you to determine voltage levels as well as frequency (the number of cycles per second). If you count the number of horizontal divisions that one complete cycle occupies on the screen, and multiply that by the time scale (for instance, 10 ms/division), you get the period, T, of the signal (the time it takes for one cycle to complete). The frequency, f, is the reciprocal of the period; the formula for f looks like this: f = 1/T. When you’re testing voltage levels, you can often use multimeters and oscilloscopes interchangeably. The choice of which tool you use is yours, though for routine testing procedures you may find the multimeter a little easier. In general, you may prefer to use an oscilloscope for Determining visually whether an AC or digital signal has the proper timing. For example, you often need this test when you troubleshoot radio and television equipment. The service manuals and schematics for these devices often show the expected oscilloscope waveform at various points in the circuit so that you can compare. Very handy! Testing pulsating signals that change very rapidly. Signals that change faster than about five million times a second (5 MHz) are hard to detect with other test equipment, such as a multimeter or logic probe. Visually testing the relationship between two signals, when using a dual-trace oscilloscope, a scope with two input channels. You may need to do this test when you work with some digital circuits, for example. Often one signal triggers the circuit to generate another signal. Being able to see both signals together helps you determine whether the circuit is working as it should. Here is a sample dual-trace display. The top signal represents the output of a 555 timer configured as an oscillator, and the bottom signal represents the voltage across a capacitor that is connected across the 555 timer output.

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Electronics: Doping Semiconductors

Article / Updated 03-26-2016

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. The atoms of a pure semiconductor, such as silicon, are held together by strong covalent bonds in a three-dimensional crystalline structure. Each silicon atom shares its 8 valence (outer) electrons with neighboring atoms. By doping a pure semiconductor material, you upset its bonds and free up charge carriers. Dopants are no dopes; they try to masquerade as one of the crystal’s atoms, attempting to bond with the other atoms, but they are just different enough to stir things up a bit. For instance, an atom of arsenic has one more outer electron than an atom of silicon. When you add a small amount of arsenic to a bunch of silicon atoms, each arsenic atom muscles its way in, bonding with the silicon atoms, but leaving its extra electron drifting around through the crystal. Even though the doped material is electrically neutral, it now contains a bunch of free electrons wandering aimlessly — making it much more conductive. By doping the silicon, you change its electrical properties: Wherever the dopant is added, the silicon becomes more conductive. Another way to dope semiconductors is to use materials such as boron, in which each atom has one fewer valence electron than does a silicon atom. For every boron atom you add to a silicon crystal, you get what is known as a hole in the crystalline structure where an outer electron should be. Wherever there is a hole in the structure, the bond holding the atoms together is so strong, it will steal an electron from another atom to fill the hole, leaving a hole somewhere else, which then gets filled by another electron, and so forth. You can think of this process as the hole moving around inside the crystal. (Well, the electrons are moving, but it looks like the position of the hole keeps moving.) Because each hole represents a missing electron, the movement of holes has the same effect as a flow of positive charges. Impurities that free up electrons (negative charges) to move through a semiconductor are called donor dopants, and the doped semiconductor is known as an N-type semiconductor. Arsenic is a typical donor dopant. Impurities (such as boron) that free up holes (like positive charges) to move through a semiconductor are called acceptor dopants, and the doped semiconductor is known as a P-type semiconductor. Boron is a typical acceptor dopant. If you apply a voltage source across either an N-type or a P-type semiconductor, the doped semiconductor acts like a conductor and allows current to flow. But if you combine an N-type and P-type semiconductor, current will flow in only one direction through the pn-junction — and only under certain voltage conditions. By creating different combinations of P-types and N-types, you create different types of diodes and transistors.

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10 Memorable Names in Electronics

Article / Updated 03-26-2016

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? Eighteenth- and nineteenth-century scientists throughout Europe and America spent many an hour probing the mysteries of electricity and magnetism, learning from their predecessors and contemporaries, and performing experiment after experiment. The following ten individuals are among the many who contributed to the birth of the field of electronics. Charles-Augustin de Coulomb (1736–1806) was a French physicist who is best known for characterizing the electrostatic force (that is, attraction and repulsion) between electrically charged particles. Published in 1785, Coulomb’s Law laid the foundation for the field of electromagnetism. The SI (International System of Units) unit of electrical charge is named the coulomb in honor of his discovery. Alessandro Volta (1745–1827) was an Italian physicist and chemist whose invention of the voltaic pile (known today as a battery) in 1799 dispelled the popularly held notion that electricity could come only from living things. Volta’s invention enabled scientists to produce electric current at will, sparking further experimentation in what would become the field of electrochemistry. Volta also dabbled in electrostatics, discovering that the electric potential (that is, voltage) across a pair of capacitor plates is directly proportional to the amount of charge on the plates — a relationship known as Volta’s Law of Capacitance. The SI unit measure of electric potential — the volt — is named for Volta in recognition of his pioneering achievements. Hans Christian Ørsted (1777–1851) was a Danish physicist and chemist who, in 1820, figured out that steady electric currents create magnetic fields. This phenomenon, known as Ørsted’s Law, was significant because at the time electricity and magnetism were believed to be separate forces. Further experimentation by Ørsted and other scientists led to the development of the field of electromagnetism. André-Marie Ampère (1775–1836) was a French physicist and mathematician who is known as the father of electrodynamics (now known as electromagnetism). Following up on the work of Hans Christian Ørsted, Ampère developed both physical and mathematical theories to explain the interactions between electricity and magnetism, publishing his theories in 1827. Well before electrons were discovered and named in the late nineteenth century, Ampere postulated the existence of an “electrodynamic molecule.” The SI unit of current, the ampere (or amp), is named after this scientist. Joseph Henry (1797–1878) was an American scientist and inventor who discovered the principle of self-induction and improved the design of electromagnets. Henry’s work in the 1820s and 1830s contributed to the development of electric relays, the telegraph, the DC motor, and the electric doorbell. The SI unit of inductance — the henry — is named for him. Michael Faraday (1791–1867) was an English physicist who is best known for discovering electromagnetic induction — that is, inducing a current in a wire that is exposed to a time-varying magnetic field — in the 1830s and for his invention of electromagnetic rotary devices (such as the electric motor), which led to the practical use of electricity in technology. The SI unit of capacitance — the farad — is named for Faraday. Georg Simon Ohm (1789–1854) was a German physicist and mathematician who discovered the proportional relationship between the voltage applied across a conductor and the strength of the current flowing through the conductor. (Georg Ohm is shown in the next figure.) Ohm published his findings, known today as Ohm’s Law, in 1827. (Another scientist, Henry Cavendish, discovered the same relationship many years before Ohm, but his experiments went unpublished until well after his death in 1810. Had Cavendish published during his lifetime, Cavendish’s Law might be used instead of Ohm’s Law and the SI unit of resistance might be a cavendish instead of an ohm.) James Prescott Joule (1818–1889) was a self-taught British physicist (and brewer) whose discovery in the 1840s of the relationship between heat and mechanical energy led to the law of conservation of energy. Joule also discovered a relationship between the heat dissipated by a resistor and the current flowing through the resistor. The SI unit of energy bears his name. Gustav Robert Kirchhoff (1824–1887) was a German physicist whose contributions to circuit theory have earned him the honor of having two laws named after him. First described in 1845, Kirchhoff’s Current Law (KCL) and Kirchhoff’s Voltage Law (KVL) tell us about the relationships between voltages and currents in DC circuits. George Johnstone Stoney (1826–1911) was an Irish physicist who postulated the existence of an “atom of electricity” in 1874 and coined the term electron in the 1890s to refer to the fundamental unit of electricity. (His name might have been the most memorable on this list had he chosen to name the atom of electricity after himself!)

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Electronics: 555 Timer as an Astable Multivibrator

Article / Updated 03-26-2016

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 the low and high timing intervals using the formulas that follow:

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Electronics: Reading Resistor and Capacitor Codes

Article / Updated 03-26-2016

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. You translate the color and position of each band into digits, multipliers, and percentages. The table that follows outlines the meaning of the resistor color bands. Color 1st Digit 2nd Digit Multiplier Tolerance Black 0 0 x1 ±20% Brown 1 1 x10 ±1% Red 2 2 x100 ±2% Orange 3 3 x1,000 ±3% Yellow 4 4 x10,000 ±4% Green 5 5 x100,000 n/a Blue 6 6 x1,000,000 n/a Violet 7 7 x10,000,000 n/a Gray 8 8 x100,000,000 n/a White 9 9 n/a n/a Gold n/a n/a x0.1 ±5% Silver n/a n/a x0.01 ±10% Capacitor value reference In electronic circuits, the value of a capacitor can be determined by a two- or three-digit code that appears on its casing. The following table outlines values for some common capacitors. Marking Value nn (a number from 01 to 99) or nn0 nn picofarads (pF) 101 100 pF 102 0.001 µF 103 0.01 µF 104 0.1 µF 221 220 pF 222 0.0022 µF 223 0.022 µF 224 0.22 µF 331 330 pF 332 0.0033 µF 333 0.033 µF 334 0.33 µF 471 470 pF 472 0.0047 µF 473 0.047 µF 474 0.47 µF Capacitor tolerance codes In electronic circuits, the tolerance of capacitors can be determined by a code that appears on the casing. The code is a letter that often follows a three-digit number, for instance, the Z in 130Z. The following table outlines common tolerance values for capacitors. Note that the letters B, C, and D represent tolerances in absolute capacitance values, rather than percentages. These three letters are used on only very small (pF range) capacitors. Code Tolerance B ± 0.1 pF C ± 0.25 pF D ± 0.5 pF F ± 1% G ± 2% J ± 5% K ± 10% M ± 20% Z +80%, –20%

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Electronics: Integrated Circuit (IC) Pinouts

Article / Updated 03-26-2016

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. So, for example, with the clocking notch orienting the chip at the 12 o’clock position, the pins of a 14-pin IC are numbered 1 through 7 down the left side and 8 through 14 up the right side.

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Important Formulas in Electronics

Article / Updated 03-26-2016

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. These laws are straightforward, but when you’re trying to solve for one variable or another, it is easy to get them confused. The following table presents some common calculations using Ohm’s Law and Joule’s Law. In these calculations: V = voltage (in volts) I = current (in amps) R = resistance (in ohms) P = power (in watts) Unknown Value Formula Voltage V = I x R Current I = V/R Resistance R = V/I Power P = V x I or P = V2/R or P = I2R Equivalent resistance and capacitance formulas Electronic circuits may contain resistors or capacitors in series, parallel, or a combination. You can determine the equivalent value of resistance or capacitance using the following formulas: Resistors in series: Resistors in parallel: or Capacitors in series: or Capacitors in parallel: Kirchhoff’s Current and Voltage Laws Kirchhoff’s Circuit Laws are commonly used to analyze what’s going on in a closed loop circuit. Based on the principle of conservation of energy, Kirchhoff’s Current Law (KCL) states that, at any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node, and Kirchhoff’s Voltage Law (KVL) states that the sum of all voltage drops around a circuit loop equals zero. For the circuit shown, Kirchhoff’s Laws tells you the following: KCL: I = I1 + I2 KVL: Vbattery - VR - VLED = 0, or Vbattery = VR + VLED Calculating the RC time constant In a resistor-capacitor (RC) circuit, it takes a certain amount of time for the capacitor to charge up to the supply voltage, and then, once fully charged, to discharge down to 0 volts. Circuit designers use RC networks to produce simple timers and oscillators because the charge time is predictable and depends on the values of the resistor and the capacitor. If you multiply R (in ohms) by C (in farads), you get what is known as the RC time constant of your RC circuit, symbolized by T: A capacitor charges and discharges almost completely after five times its RC time constant, or 5RC. After the equivalent of one time constant has passed, a discharged capacitor will charge to roughly two-thirds its capacity, and a charged capacitor will discharge nearly two-thirds of the way.

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