Practical Electronic Circuits A Strong Foundation for Creating Electronic Projects By A. B. Lawal Copyright © 2019 by AB Prominent Publisher All rights reserved. ISBN: 9788835341215 Published in the United States Limit of Liability/Disclaimer of Warranty All information given in this book is based on my own research and does not constitute technical or financial advice. The author and publisher cannot be held responsible for the consequences of actions taken, or any consequences through inaction, as a direct or indirect result of the information in this book. All information is used at your own risk. Whilst all content is checked for accuracy, no information contained within this book or in any of its links is to be used without taking technical, professional and marketing advice first. Anyone seeking advice should consult an Independent Advisor. The author of this book is not liable or responsible for any other websites or services linked to or from it. It is forbidden to reproduce any part of this book in any form or medium. Reselling is prohibited. Table of Contents Preface About the Author 1. Fundamentals of Electronic Circuits 1.1 Power Supplies & Electronic Signals 1.1.1 Power Supply 1.1.2 Electronic Signal 1.2 Electricity: Charges & Current 1.2.1 Electric Charge 1.2.2 Electric Current 1.2.3 Current Drawn By Common Electronic Devices 1.3 Electric Voltage, Grounds & Power 1.3.1 Electric Voltage 1.3.2 Grounds 1.3.3 Electric Power 1.3.4 Electric Heat 1.4 Conductors, Resistors & Semiconductors 1.4.1 Conductors, Insulators & Resistivity 1.4.2 Electrical Resistance & Resistivity 1.4.3 Conductivity 1.4.4 Good Conductors, Poor Conductors & Semiconductors 1.4.5 Semiconductors 1.5 Resistor Symbols, Types & Color Codes 1.5.1 Active & Passive Components 1.5.2 Resistor Symbols 1.5.3 Ohm’s Law 1.5.4 Types of Resistors 1.5.5 Thermistor 1.5.6 Varistor Resistor 1.5.7 LDR (Light Dependent Resistors) or Photo Resistor 1.5.8 Surface Mount Resistor (SMD) 1.5.9 Standard Resistors 1.5.10 Resistor Tolerance 1.5.11 The E-Series 1.5.12 How to Read Resistor Color Codes 1.5.13 How to Read 4-Color Coded Resistors 1.5.14 Zero-Ohm Resistor Practice Exercise 1: Reading Color Codes 1.5.15 How to Read 5-Color Coded Resistors 1.5.16 How to Read 5-Color Coded Resistors with Reliability Band 1.5.17 How to Read the Color Codes of Surface-Mount (SMD) Resistors 1.5.18 How to Read 6-Color Coded Resistors with TCR 1.5.19 How to Understand Resistor Power Ratings Practice Exercise 2: Building a Current-Limiting Circuit for an LED 1.6 Resistor Networks: Series & Parallel Combinations 1.6.1 The Series Combination 1.6.2 The Parallel Combination 1.6.3 The Voltage Divider Circuit: How to Use Resistors to Tap Voltages Practice Exercise 3: Building Resistor Networks & Divider Circuit 1.7 Open, Closed & Short Circuits 1.7.1 Difference Between Open & Closed Circuits 1.7.2 Short Circuits & Dangers of Overloading 1.8 Electrostatic Charge Protection 1.8.1 How to Protect Electronic Components from Static Discharges 1.9 Electronic Switches 1.9.1 Categories of Switches 1.9.2 Types of Switches Practice Exercise 4: Using DPDT Switch to Control Light & Alarm Circuits 1.10 Understanding Wires, Cables & Wire Gauges 1.10.1 Difference Between Wire & Cable 1.10.2 Wire Gauges 1.10.3 Types of Cables Used in Electronics & Telecommunication 1. How to Set up A Modest Workshop for Yourself 2.1 Where You Can Set up A Modest Workshop 2.1.1 The Essential Ingredients of a Good Workshop 2.2 The Basic Hand Tools for Your Workshop 2.3 Basic Electronic Components for Your Workshop 1. Workshop Safety: How to Stay Safe 3.1 General Workshop Safety 3.2 Personal Workshop Safety 3.2.1 Soldering Safety 3.3 Safety from Unexpected High Voltages 1. More Helpful Resources Conclusion Preface This book Practical Electronic Circuits: A Strong Foundation for Creating Electronic Projects is designed to provide skills and a hands-on practical experience for students of electronic engineering and computer science. It also provides a good foundation for anyone interested in learning how to create electronic projects. Electronics curricula are densely packed in many engineering and computer science colleges. This book therefore is a great help because it treats each topic thoroughly. So it is a great companion. The book will be of great help for your electronics education because it is filled with simple and moderately complex practical projects. Links to stores where you can get very cheap electronic parts to work with are also included. You will also learn how to be safe in your workspace, and how to develop the courage you need to carry out any electronic project. A step by step approach is used to explain the process of carrying out an electronic project. This book is also a great value for every electronics students undergoing technical training. It encourages them through providing useful technical advice needed in a highly practical environment, with a clearly defined problem so they do not get stuck while building even complex projects. About the Author A. B. Lawal is a control and instrumentation Engineer. He also has a master’s degree in computer science. He worked for a couple telecommunication companies for over 10 years before becoming a lecturer in a prestigious engineering college in the United States. He is currently involved in evaluation, revision, redesign, and expansion of electronic systems and technically related computer programs. 1. Fundamentals of Electronic Circuits 1.1 Power Supplies & Electronic Signals In this chapter, I lay some important groundwork that you need to make sense of the rest of the book. I examine the bits and pieces that make up the most common types of electronic devices, and that make electronic circuits in general to work. All electronic and electrical devices, from the simplest flashlight to the giant and complex control systems on a modern aircraft, all need one thing in common: power supply . 1.1.1 Power Supply A power supply is a source of electricity, or more precisely, a source of electrons . Without power supply, an electronic device is all just a pile of inactive plastic, metal or silicon (among other things). A few examples of power supplies are batteries, power adaptors for charging your mobile phones and laptop computers and so on. Fig. 1.1.1 shows a power supply built by assembling a few batteries. However, a power supply itself can be built with electronic devices, such as shown in Fig. 1.1.2 and Fig. 1.1.3 . Fig. 1.1.1: 12V DC Battery Power Supply: Source: Superbrightleds.com Fig. 1.1.2: A Laptop Charger. Source: waveform.com Fig. 1.1.3: Power supply of a desktop computer. Source: avnet.com Next, I take a look at the basic concept underlying all electronic circuits: signals . I’m not going to bore you with any complicated or tedious or physics concepts, but I want to warn you from the start. In order to learn how electronic circuits work and get to a level where you can design and build your own electronic devices, you need to have at least a basic idea of what a signal is. So put on your thinking cap and come with me. Fig. 1.1.4 shows various symbols used for representing DC and AC power sources in electronic circuits. The positive terminal of a DC power supply is usually represented by “ +” while the negative terminal is represented by “ ─‘’ . Fig. 1.1.4. various symbols for circuit power supplies As shown in Fig. 1.1.4, the + terminal of bi-polar junction transistor circuits is often represented by V CC , while the + terminal of FET and MOSFET circuits is often represented by V DD . We will look at FET (field effect transistor) and MOSFET (metal-oxide-semiconductor transistor) circuits later. 1.1.2 Electronic Signal In the field of electronics, a signal is an electric current or electromagnetic field used to transmit data from one place to another. DC ( Direct Current ) is the simplest form of signal because it travels in only one direction so it can be switched on or off. It is the principle behind the working of the early telegraph . AC ( Alternating Current ) on the other hand is a type of current that pulsates or changes direction periodically. Electronic devices process AC signals very often. Such signals are electromagnetic carriers of one or more data streams. Fig. 1.1.5 shows graphical representations of DC and AC signals. Fig. 1.1.5: DC signal (left) and AC signal (right). A very common source of alternating current is the mains , which is usually obtained from the electric sockets on the walls of your room or office. Mains is usually supplied by the electric power authority in your locality. Fig. 1.1.6 . Fig. 1.1.6: Mains sockets. Source: Rapidonline.com Before I move on to the next section I must mention that the oscilloscope is a very good example of both DC and AC signal sources often used in electronics labs. See Fig. 1.1.7 . You will learn how to use the oscilloscope later. Fig. 1.1.7: A 70MHz 2-Channel analogue oscilloscope. Source: https://amzn.to/2D6N3ON 1.2 Electricity: Charges & Current Even though we don’t know exactly what electricity is, we do know a lot about what it does and how it behaves. You will find it easier to understand electricity if you avoid using the term electricity itself to describe it. The reason is very simple: The word electricity is not very precise. Scientists and engineers use the word electricity to refer to a few different but related things. The most common ones are rather precise names like electric charge, electric current, electric field, and electric energy . All these are what are commonly called electricity . 1.2.1 Electric Charge Electric charge, electrical charge, electrostatic charge, or simply charge, is the characteristic of a unit of matter that expresses the extent to which it has more or fewer electrons than protons. In an atom, it is the electron that carries a negative elementary or unit charge and the proton carries a positive charge. The two types of charge are equal and opposite. For practical purposes, the most important thing you should know about electric charge is that opposite charges attract and similar charges repel . In other words, negative charges attract positive charges positive charges attract negative charges negative charges repel negative charges positive charges repel positive charges Therefore an electron and a proton attract each other, but an electron repels another electron and a proton repels another proton. The unit of electric charge is coulomb (symbol is C ). 1.2.2 Electric Current An electric current is defined as the rate of flow of electric charge past a given point or region. We say an electric current exists when there is a net flow of electric charge through a given point or region. In electric circuits this charge is often carried by electrons moving through a wire. In other words, electric current is the total charge that passes through a given cross-sectional area A per unit time. This cross-sectional area is frequently represented by a slice through a solid material, such as a conductor (for example, a copper wire). Fig. 1.2.1: ΔQ Charge crosses a conductor of cross-sectional area A in Δt time. Supposing Δ Q represents the amount of charge that passes through an area in a given time interval Δ t as shown in Fig. 1.2.1 . , then the average current I ave is defined as: The SI unit (international system of units) of current is therefore coulombs per second or C/s, but the ampere (A) is often preferred. So 1 A = 1 C/s. The ampere is a rather too large a unit for practical uses in electronic circuits, so you will find it more convenient to express current in milliamps (mA), microamps (A) or nanoamps (A). 1 mA = 1 × 10 -3 A, 1 μA = 1 × 10 -6 A, 1 nA = 1 × 10 -9 A. 1.2.3 Current Drawn By Common Electronic Devices When tinkering with circuits in general, it is good to have idea of how much current common electronic and electrical devices (commonly called loads ) draw from their power supplies. Below are some examples: A 100-watt lightbulb (electrical device): about 1 A; A laptop computer (electronic gadget): between 2 to 3 A; A microwave oven (electrical device): about 10 A; A fluorescent light: 1 to 2 A; A radio or stereo set: (electronic): 0.5 to 3 A; A typical LED (a small electronic indicator light): 20 mA; A microchip (electronic): a few μA or even perhaps several pA A current sufficient to induce a cardiac or respiratory arrest: about 100 mA to 1 A. A mobile (smart) phone: around 200 mA An electric fan (electrical device): about 1 A; A TV set (electronic gadget): 1 to 3 A; A toaster (electrical gadget): 7 to 10 A; An automobile starter: around 200 A; A lightning strike: about 1000 A. Electric current can be measured by a ammeter but a digital multimeter is often used in electronics because it has higher precision and can measure various ranges of current. We will look at the multimeter and how to use it in chapter 7. In electronic circuits, an ammeter is represented by Fig. 1.2.2 shows an analogue DC ammeter and Fig. 1.2.3 shows a digital DC ammeter. Fig. 1.2.2: An analogue DC ammeter, range 0 to 3A. Source: School Specialty Canada Fig. 1.2.3: An digital DC ammeter, range 0 to 10A. Source: Arbor Scientific 1.3 Electric Voltage, Grounds & Power 1.3.1 Electric Voltage In their natural state, the electrons in a conductor such as a copper wire freely move from one point to another, but in a completely random way. To make them all move together in one and the same direction, all you have to do is give them a push . In other words, electric voltage can be thought of as a kind of “electrical pressure”. The technical term for this push is electromotive force , abbreviated EMF , or sometimes simply E . But it is more commonly known as voltage . Technically speaking the voltage is also referred to as a potential difference or just potential — they both mean the same thing. This means that potential difference or voltage is a relative word since you can only measure it across two points, one of which may the reference point called ground . For example, if we say that a point in a circuit has a voltage of 12 V it is meaningless unless we have another point in the circuit (which may be the ground) with which to compare it. Electric voltage can be measured by a voltmeter but a digital multimeter is often used in electronics because it has higher precision and can measure various ranges of voltage. In electronic circuits a voltmeter is represented by Fig. 1.3.1 shows an analogue DC voltmeter and Fig. 1.3.2 shows a digital DC voltmeter.