Build Your Own Electronics Workshop
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About this ebook
Whether electronics is a hobby or an avocation, this resource covers everything you need to know to create a personal electronic workbench. The author includes essential yet difficult to find information such as whether to buy or build test equipment, how to solder, how to make circuit boards, how to troubleshoot, how to test components and systems, and how to build your own test equipment.
- Building on a budget
- Sources for equipment
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Build Your Own Electronics Workshop - Thomas Petruzzellis
INTRODUCTION
Build Your Own Electronics Workshop was created to assist newcomers in electronics who wish to learn how to build their first electronics workbench. This book is designed for electronics hobbyists, enthusiasts, technicians, and recent graduate engineers, alike, who are new to the field of practical electronics. The electronics workshop is a specially designed place where one can go to work on an electronics project such as testing electronic components, troubleshooting a piece of electronics or radio gear, or building a new electronics project or kit. The electronics workshop is a place where you can work undisturbed and leave an ongoing project to find it untouched and undisturbed when you return. Building your new electronics workshop will free you from building projects on the kitchen table and the terror of returning to the table to find your project thrown in a box, with small components tossed everywhere. This book will help you to construct an efficient new electronics workshop that is well lit and well ventilated, a work area that houses your special test equipment and tools where you can work undisturbed.
The book covers many topics such as how to locate a suitable area of your home, basement, or garage to set up your new electronics work area; whether to build or buy your new electronics workbench; lighting and ventilation; and power requirements. You will learn what the essential pieces of test equipment, components, and tools are and how to use and purchase them. You will learn how to purchase test equipment, components and tools. The book will also help you to read schematics, design and build circuit boards, as well as build your own pieces of electronic test equipment. You will learn how to solder and how to construct circuits using different practical circuit-building techniques. The book will also present methods on how to test electronic components as well as many formulas, charts, and resources for the electronic enthusiast.
Chapter 1 discusses what is needed to create your electronic workshop in your home. Many ideas for constructing your electronics workshop are presented, including layout, type of workbenches, building or buying your electronics workbench, power requirements, lighting, ventilation, and backup power concepts.
Chapter 2 discusses the multimeter, perhaps the single most important item that you will have on your electronics workbench. Topics covered include the differences between analog and digital multimeters, how to use a multimeter, what kinds of tests you can perform, and the importance of good test leads.
Chapter 3 presents the oscilloscope, the engineer and technician’s best friend. With the oscilloscope you can troubleshoot just about any problem in electronics. Differences between analog and the digital scopes are discussed, then analog to digital PC cards that function as oscilloscopes are examined, followed by test leads and probes, the most important controls and how to operate them, and, finally, how to care for your oscilloscope.
Chapter 4 highlights the function generator, a very useful addition to the electronics test bench, for testing logic circuits, filters, and amplifiers. Different types of function generators are discussed, from simple signal generators to the more complex function and arbitrary pulse generators. Practical uses of function generators as well as how to build your own low-cost function generator are also covered.
Chapter 5 discusses the last of the big four
pieces of test equipment that you should have on your electronics workbench—the frequency counter. The frequency counter is often used in conjunction with the signal generator and oscilloscope when troubleshooting and constructing new electronics circuits. In this chapter you will also learn how to construct your own 1 gHz frequency counter.
Chapter 6 takes a look at other important test equipment that you might want to obtain for your electronics workshop. These secondary pieces of test gear make solving electronics problems easier. The function or signal generator, frequency counter, battery testers, capacitor testers, LC testers, inductance meter, logic injectors, logic probes, IC testers, clamp-on ammeters, and tube and transistors testers are discussed.
Chapter 7 covers power supplies, perhaps the single most important piece of equipment you can have on your new electronics workbench. Different types of power supplies are discussed, including lab, dual-power, and dc-to-dc power supplies, as well as whether to buy or build them, and, finally, how to construct your own lab power supply.
Chapter 8 revolves around a discussion of batteries and battery power supplies. This chapter delves into the differences and similarities between various types of batteries and their characteristics, and how and when to use them, as well as how to charge them most efficiently. This chapter also shows how to build a battery charger for a 12 volt battery, a solar battery charging system, and a backup power source that uses a deep-cycle 12 volt battery and an inverter.
Chapter 9 discusses electronic components such as resistors, capacitors, inductors, transformers, and semiconductors, their basics, how and when they are used, and their characteristics. Also discussed is how to connect them in a circuit, series and parallel connections of components, and so on.
Chapter 10 explains how to test electronic components such as resistors, capacitors, transistors, batteries, SCRs, and MOSFETs. In this chapter, you will learn how to test electronic components using both the multimeter and the oscilloscope. Simple tests and tricks are presented.
Chapter 11 presents a number of electronics troubleshooting techniques and approaches to help you solve your future electronics repair problems. It begins by discussing signal tracing and signal injecting techniques for testing circuit stages in analog equipment such as oscillators, amplifiers, and power supplies, and explains how to eliminate circuit problems such as unwanted oscillations and distortion. This chapter also discusses some troubleshooting techniques for servicing digital circuits and microprocessors.
Chapter 12 is all about various hand tools that would be useful around your electronics workbench, the must have
or primary tools, such as drills, screwdrivers, needle-nose pliers, knives, wire cutters, and hemostats, and various other types of important tools you will find invaluable in your electronics workshop. It also talks about the care and cleaning of tools.
Chapter 13 presents the topic of soldering, what soldering irons to purchase, as well as what types of solder to buy, and the soldering gun versus the soldering iron. Soldering techniques for both point-to-point wiring as well as circuit-boards are discussed. This chapter also discusses the care of soldering tools and how to make good solder joints, as well as how to construct your own solder-station controller.
Chapter 14 covers the extensive topics of circuit fabrication, from point-to-point wiring techniques to wire-wrap techniques, perf-board construction, and protoboard circuit building. This chapter also discusses circuit building, from designing circuits using CAD/CAM and layout software to different aspects of making your own circuit boards.
Chapter 15 presents the subject of purchasing test equipment, where and how to buy equipment, and what to look for. It also discusses how and where to purchase electronics components and workshop tools, and how to save money as a smart consumer. The topic of buying versus building your own test equipment is also covered.
Chapter 16 features several pieces of test equipment you can build. You can save money by building your own equipment and learn a lot in the process, not to mention the great feeling that you get when you create your test gear. This chapter will show you how to build a continuity tester, ESR capacitor tester, logic injector/probe, capacitance/inductance tester, transistor tester, Zener diode tester, electronic fuse, and a pulse generator.
The Appendix presents many useful electronics charts and formulas, and lists of companies offering all types of electronics products, including test equipment, components, circuit boards, tools, work benches, and books, which could be useful in your electronics hobby or career.
Build Your Own Electronics Workshop will give you a good introduction to the many aspects involved in setting up and building your own electronics workshop. It will be useful and serve you well, both in the present and in the future, whether electronics is your occupation or avocation.
I would like to thank the following people and companies for their help in creating this book: Judy Bass, Senior Electronics Editor for technical publications at McGraw-Hill, for her vision and helpful suggestions throughout; Neil Heckt and Almost All Digital Electronics for details of the L/C meter project; and Tony VanRoon for the information and diagrams in Chapter 7. A special thank you is due the American Radio Relay League for the use of diagrams, schematics, and information used within. Many thanks are also due the following companies for use of photos and data sheet information: Exar Corp., Tektronix Corp., Protek Test Equipment Corp., Electronic Design Specialists, Microchip Corp, and Phillips Corp.
CHAPTER 1
The Electronics Workshop
The electronics workshop is an essential place for the electronics enthusiast, the electronics technician, and the electronics engineer. It is akin to the woodworker’s workbench, the jeweler’s workbench, and the machinist’s workbench—a place set aside for a particular interest or work activity. Each particular area of interest, hobby, or skill requires a workbench—a place where a particular type of work activity is done. It is usually a place set aside in a basement or spare room, or even in a garage or attic, where you can work undisturbed; a separate area in which work can be left on the table, untouched until you can return to your building, testing, or troubleshooting a project. It is essential that a reserved space be set aside so work can be left undisturbed until you can return to it. This is the main reason why the kitchen table is not suitable as an electronics workbench, since every day you would have to set up your workbench and begin anew.
The electronics workshop is no different than any other specific work area or place where a particular type of work can be performed, except that you probably will need specific types of tools, instruments, or test gear to complete the electronics job at hand, whether it be building a particular piece of electronics circuitry or troubleshooting or repairing a piece of equipment. Working with electronics generally requires special equipment and tools for building, testing, and troubleshooting activities.
A distinction is often made between the electronics workshop and a general or conventional workshop. A general workshop might best be described as a work area where you might cut wood, assemble a wagon, or construct a wooden toy. An electronics workshop or workbench might be described as a specific area in which you work on electronic projects. Electronics projects are generally smaller projects than, say, building something with wood or a plumbing project. Working on an electronics usually requires specific tools and test equipment for electronics project work. A distinction is generally made between a general workshop, a woodworking shop, or a metalworking shop versus an electronics workbench or workshop. Although it would be possible to work on a woodworking or metalworking project at your electronics workbench, an electronics project is usually much cleaner—there are no wood chips, metal filings, or oil puddles. Electronic circuits should be free of metal chips, which are usually fatal to them, and oil can be conductive and should be kept away. So our focus will be on an electronics workbench with a clean work top with a nonconducting, antistatic mat and a notebook or two. A typical electronics workbench might contain nonelectronic tools such as soldering irons, wire cutters, and small screwdrivers, as well as test equipment such as multimeters, oscilloscopes, and frequency counters.
In order to set up your new electronics workshop, you will first need to select a free room or section of a room where you can carve out an area that you can call your own. This could be in your basement, attic, closet, garage, or even in a section of a barn. You will need to take some time and figure out where you will want to spend time working on your hobby or vocation. The electronics workbench area should be comfortable and have an adequate heating/cooling system so you can be comfortable over a period of a few hours or so at least. If you are working on a kit or troubleshooting project, you may need to spend a number of hours in an undisturbed area that is comfortable to work in. There is nothing worse than working in an area that is either too hot or too cold for any length of time. Being uncomfortable will seriously affect your overall concentration.
Next, you will need to determine how much space you will actually need to set up your electronics workshop area. You might desire a large area or an entire room but, in reality, what will your particular situation permit, that is, what will your spouse or roommate allow? Ask yourself this question: Do you want to have your electronics workbench adjacent to or near your wood or metal workshop or in a different area altogether? If the electronics workbench area is going to be separate from other work areas, then you will need less room. Since a separate electronics workbench might likely be a cleaner area than, say, a woodworking shop or a general workshop, it may be possible for it to share a room with another workbench—half the room for electronics project and the other half for crafts, sewing, or some other activity.
There is an important psychological aspect to determining space considerations for your electronics work area. Many people, especially artists and writers, believe that having a dedicated work space is essential in doing productive work, a space that is respected by others and where concentration can be maintained. This concept can be extended to work areas for metal- or woodworking and other creative hobbies. So you many want to further consider space
as more than just a place to fix, build, or test an electronic circuit. Writers, for example, need a quiet space in which to work, often for many hours at a time, without being interrupted or disturbed by children or others. When you are in your private work space, immediate demands, such as taking the garbage out or watering the lawn, are temporarily suspended. Many view their work area as a refuge where things or projects are left undisturbed, but this also extends to privacy and a respect for your need to get something accomplished without being disturbed. When in your private space or work area, your space and projects are to be respected by others. It can be a place to get away from the noise of the family—the din of the television, the barking dog, and the kids crying—in order to concentrate on the project or tasks at hand, whether it is reading a manual, soldering a circuit, or writing about a project. The concept of dedicated space
is extremely important, especially if your electronics workshop is the place where you earn your livelihood. Or it can be considered as a space for getting away from the family or others for a period of time. However, the dedicated space
issue is also a matter of balance. You cannot just lock yourself up in your room forever and totally escape your family and responsibilities. Your dedicated space
should be respected by others but not abused by you in the avoidance of others at all times.
Next, you will need to determine if you want to buy or build your workbench and whether you want to have a metal or wooden workbench. Metal workbenches are often available through Sears stores or building supply stores such as Home Depot. Metal workbenches are generally more expensive and limited to certain sizes. They have the ability to be grounded well but, on the other hand, if you are working on a hot
chassis, that is, a circuit without isolation, then it is possible to get a nasty shock or to damage the equipment you are working on. If you plan on buying or building a metal workbench, then you should consider placing a thin foam, wood, plastic, or Formica sheet on the top to isolate the bench from the circuits that you will be working on. The steel bench shown in Figure 1-1 shows a commercial metal workbench fitted with a wood top. The workbench shown in Figure 1-2 shows a two-tier metal workbench with an insulated work top. The second tier can be used for electronic test equipment. The alternative workbench featured in Figure 1-3 shows a two-tier metal workbench with an inlaid insulated work top. The workbench shown in Figure 1-4 shows yet another type of two-tier steel bench with insulated work surface and a full set of drawers that can be used to house special tools, schematics, fuses, jumper cables, and so on.
Figure 1-1.
Figure 1-2.
Figure 1-3.
Figure 1-4.
You might be able to locate a surplus steel workbench from office liquidator in your area or through a mail order business. Another option is to obtain and older, large metal desk with drawers, or even a large metal work table that could be used as an electronics workbench.
Many people prefer wooden workbenches since they are easy to build and are often available through building supply stores such as Lowes or Home Depot in the form of kits made from two-by-fours, for about $50 to $60. Wooden workbenches can be easily built from scratch if desired, using two-by-fours and wooden doors placed over a wooden frame. Another option is to use two or three sawhorses with a wooden door placed over them; this is bit less stable but can be made more secure. Another, more stable option for creating your own electronics workbench is to locate two low-cost, two-vertical-drawer file cabinets and place a six- or eight-foot-long wooden door over them. An alternative to using a door for a workbench top is to locate a surplus or low-cost overstock Formica countertop. Simply place the countertop or wooden door over the two file cabinets and secure the file cabinets to the top using recessed machine screws or large velcro pads.
Building or buying a wooden workbench will allow you to easily construct shelves above the table top in order to create separate cubbyholes for your test equipment. The shelf unit can then be placed above the workbench top and secured in place with screws if desired.
The electronics test bench shown in Figure 1-5 shows a well-organized old wood desk setup. The electronics workbench in Figure 1-6 shows a wooden door placed over wooden file cabinets with some vintage gear. The electronics test bench shown in Figure 1-7 is a wood-topped metal bench with test gear.
Figure 1-5.
Figure 1-6.
Figure 1-7.
Another option for building your electronics workbench would be to look for a computer table that has lots of cubbyholes and/or shelves to hold test equipment. These computer tables are often available as low-cost kits that can be constructed in an evening or two. This is more of an instant approach for those who are not comfortable with building their own wooden or metal electronics workbenches from scratch or plans. Computer tables are available in many different styles and types and are available from both computer stores and discount retailers.
You will also need to consider the lighting of the area that you are thinking of adopting for your new electronics workshop or workbench area. Good lighting is important in order to see and identify small parts. Poor lighting will cause eyestrain when working over a long period of time, which will cause headaches. If possible, choose an area that has good exposure to natural lighting in order to supplement your workbench lighting. Setting up your work area near a window is preferable to a dark, unlit corner. You will also need to obtain extra lighting for your electronics workshop area. Incandescent lamps do not really light work areas very well. You should consider a bank of at least two dual-fluorescent-lamp fixtures to light up the work area in order to see well enough to work with delicate parts and to solder in confined spaces. You should also consider spot
lighting, which will light up a specific area on your workbench, that is, the area in which you will be building, soldering, or testing. High-intensity spot
lamps or jewelers lamps would be a good solution. Another consideration for lighting and seeing small work is to use one of those lighted magnifier lamps that mount to the side of a table or bench. These magnifier lamps are readily available through parts and tool suppliers. Also consider purchasing a magnifying glass or the Radio Shack lighted handheld microscope/magnifier (catalog no. 63-851). This device is an invaluable aid in working on electronics projects, from identifying components to looking for bad solder joints on a circuit board.
Once the appropriate electronics workshop area has been selected, and once you have built or secured your workbench, you will need to make sure that power is readily available. You may need to determine if you will be working solely with 110 volts or if you have the need to work with 220 volts or more as you are setting up your electronics workshop. You will need to ensure that there is power available alongside or above your workbench area. You should install at least two quad outlets very close to eye level above your electronics workbench. Purchase at least one and possibly two 110 volt power strips with good power spike
protection. Power line spikes are often the cause of damage to sensitive electronics equipment. The last thing you want is to have your expensive electronic test equipment damaged by power line spikes or glitches. Power line spikes usually result from inductive loads switching on and off. Nearby loads such as freezers, vacuum cleaners, saws, and motors can cause power line spikes. Operating nearby saws and shop equipment can readily cause these spikes to be sent down the power line, directly to your sensitive test gear. Purchase the more expensive spike protection power strips such as the Tripplite Isobar series, that cost about $40 to $70. These power strips will provide an excellent level of protection for your test equipment, which through time will represent a sizeable investment.
Power protection is one of the most overlooked consideration for both computer and test equipment. Its not a fun or flashy
purchase and is thought of as dull and uninteresting, but is not to be overlooked. After accumulating hundreds and maybe thousands of dollars worth of test equipment, why not spend a few extra dollars to protect your investment. These power protection strips can be mounted on the side or at the top rear of the workbench, so that test equipment and equipment under test can be powered through it. Mounting the power strips should be planned so that gear can be quickly plugged in and unplugged without breaking your back. One idea is to mount the power strips right near the quad outlet boxes or at the back or to one side of your electronics workbench.
After your lighting and power needs are met, you should next consider a ground rod connection at your workbench if possible, in order to provide a good ground to circuits under test or for radio equipment grounds. Be sure to connect your ground rod to the electrical power ground system to ensure a good stable ground system, free of floating ground potentials.
Next, you will need to begin thinking about where to place the pieces of test gear that you have to work with. This may initially only consist of a few hand tools and/or a multimeter and soldering iron, but as money permits, you will want to add more and more test equipment. Birthdays, holidays, and Christmas are great times to ask for those needed pieces of test equipment. Eventually you will acquire all the necessary pieces of test equipment and tools to make your electronics life easier. So make sure that your electronics workbench has the ability to expand, to house your future needs for important test equipment.
When designing your electronics workbench area, you should also consider extra space to store electronic components, batteries, chargers, fuses, notebooks, and so on. We will discuss these items in more detail later on.
Another often overlooked consideration when setting up and using your new electronics workbench is ventilation. The room chosen for your electronics workbench area should have adequate air circulation if possible. A window in the room will provide not only light for your work space but the ability to let in fresh air if needed, and this becomes a serious issue if you do a lot of soldering, cutting, sanding, Dremel work, or deburring of metal or plastic parts. You may want to consider a method for keeping a nearby window open when you are working in your electronics workshop. You may also want to consider placing a fan near the window, either to let cool air inside the room or to remove tainted air from the room, as the conditions dictate.
Many people have serious allergies to smoke, dust, and strong smells, and attention should be paid to this issue, especially if you have allergies. People with allergies may have to take additional precautions against these problems, especially if working in small or confined spaces for long periods of time. If your electronics workbench area is separate from your metal- or woodworking area, you may not have the problem of wood or metal dust but there is still the problem of solder smoke removal. Many people who have allergies are seriously affected by solder smoke. If you do a lot of soldering in a confined space for a period of hours, you may become light-headed or sick from solder fumes. To avoid getting sick or having sinus infections, it is important to consider a spot
ventilation system for removing solder fumes. Many people who are allergic to strong odors or smells become more sensitive over time and their allergy problems get worse, so planning ahead will save you from more complex allergy problems later in life.
There are two approaches to solder-smoke or fume removal. One method utilizes a fan that sucks the fumes into a carbon filter that absorbs them. The filter material has to be replaced after a period of time. The second method of solder-fume removal is to vent the fumes away from your work area. You could use a plastic vacuum cleaner hose held in place by a wood or metal stand near where the soldering takes place. The opposite end of the plastic hose is either vented to another room or the outside, using a small muffin
or computer fan. Commercial fume removal systems are available from various mail order tool companies. With some ingenuity, you can design and build your own solder-smoke removal system.
Purchase a new kitchen trash can for your spouse or roommate and use the old trash can next to your electronics workbench to discard your electronic trash items.
Work Mats
Now that your electronics workbench has been constructed and everything is oriented just the way you want it, you will need to provide a clean, clear area in the center of the bench or table where you can work on building new circuits or troubleshooting circuits, running test setups, or drawing circuit schematics. In this clear center area of your electronics workbench, you should place a 12 to 18 inch piece of heavy paper or card stock or an antistatic work mat, described below. This work mat area will give you a highlighted special work area, separated from the rest of the workbench. It will make it easier to see and identify small components, parts, and hardware and will also provide a good work surface.
Once your electronics workshop or workbench has been constructed and you settle in to troubleshooting, designing, and building electronics circuits, you will likely soon encounter sensitive electronics components such as FETS, JFETS, and MOSFETS. The sensitive electronic components can be damaged very quickly if proper precautions are not taken when handling them. When working with sensitive electronic components such as MOSFETS, JFETS, CMOS transistors, and some sensitive op-amps, you need to pay particular attention to the buildup of static electricity. Make sure you are grounded when installing sensitive electronics components. Purchase an antistatic wristband, which goes around your wrist at one end while the other end connects to the ground lug of a 110 volt outlet. These are available from electronic supply houses and mail order suppliers and perhaps at your local electronics parts store. Also consider purchasing an antistatic work mat on which sensitive electronics components can be sorted and handled. The diagram shown in Figure 1-8 illustrates an electronics workbench connected to a ground system.
Figure 1-8. (Courtesy 2003 ARRL Handbook.)
The antistatic work mat is the ideal place for assembling a circuit board. It can be grounded like your antistatic wristband. Static-sensitive components are usually always packaged in antistatic bags for shipment. Place the antistatic bag on the work surface area of your electronics workbench. Next, put on the antistatic wristband and ground yourself by touching a duplex outlet box. Make sure that there are no carpets under your electronic workbench to generate static electricity. Once you are positioned in your work area, you can proceed to open the antistatic package, remove the components from the bag, install the component in the circuit, and proceed to solder the components. The main caveat to remember when handling static-sensitive components is to seat yourself, with your antistatic wristband on and grounded, and to not move around from that point until the components are soldered in place. Moving around, especially on a carpet, while handling or removing components is an invitation to disaster. These simple steps will help to ensure that you will not destroy expensive sensitive electronic components before they are utilized.
The problem of static buildup, of course, is a problem associated with the cold, dry winter months but these precautions should be practiced at all times. There is nothing worse that ordering new MOSFET components for an ailing circuit for yourself, friend, or customer only to damage it during poor handling and having to order the part over again. Once you have handled or repackaged sensitive components or finished building a new circuit, you will need to either remove the anti-static mat or place a clean, non-conducting rubber mat or heavy paper or card stock under directly under your current project before applying power to the new circuit. If your workbench is large enough, you could have an antistatic building–handling area and a separate nonconducting work area for hot
or powered projects.
One common mistake when working on open-frame electronics chassis and new electronic circuits is having conductive paths under your project. This is not a problem when you are constructing a circuit or project, but once power is supplied to a circuit, you want to make sure that there are no cut wire leads, foil, screws, antistatic mats, or anything else under your project. You need to be constantly aware of the surface under your current hot
or powered project.
Test Equipment Considerations
If you are just starting out in electronics and want to set up your own electronics workbench and you have a limited amount of money with which to buy or build some test equipment, where would you start? What is essential when you have a limited budget and/or equipment? The most essential pieces of electronic equipment would likely be a single- or dual-voltage power supply, a multimeter, a simple continuity tester, and a few hand tools, such as a set of screwdrivers, a pliers, wire cutter, hammer, and soldering iron.
Multimeters are very important pieces of test gear. Multimeters are relatively inexpensive now and can perform many different functions around your electronics workbench, including measuring voltage, current, resistance, and temperature and transistor gain. When purchasing a multimeter, consider buying a medium- to higher-priced meter. Many cheap multimeters can only measure dc voltages and resistance. A slightly higher-priced model might measure dc and ac voltages but not current. Look for a meter that will measure both dc and ac voltages as well as ac and dc current in a number of ranges. Current ranges up to 10 amperes are desired if possible, if you will be testing appliances. Look for a multimeter that measures dc resistances in at least three or four different ranges, from 200 ohms to 10 megohms or higher.
Higher-priced models might also feature a continuity tester, which is very useful, or perhaps an hFe or transistor gain measurement feature or a capacitance meter feature. More expensive models might also have a temperature probe option, which could be useful.
When buying a multimeter, you might also come across a meter that features an RS-232 data-logger. These meters have a computer interface and software that let the multimeter act as a computer data-logger. This feature is very useful if you want to measure voltages over time and graph them later. If you are testing circuits with intermittent problems or trying to establish if the power circuits are stable, then this type of meter might be very useful to you. For example, you could leave your recording digital multimeter on the bench to monitor the stability of voltage of an intermittent circuit overnight and have the meter log results over time.
As money permits, you could jump up to the next level and purchase a used or new oscilloscope. The oscilloscope is one of the most important and useful pieces of test gear that every electronics enthusiast should eventually purchase.
When setting up your new electronics workbench, you will need to decide if you can afford new or used test equipment. Used test gear can have many more years of useful life left on it if you purchase quality equipment from a used test equipment vendor. If you want to buy used gear, stick with name brands like Fluke, Tektronics, and HP. Of course, your other option is purchase new equipment if your budget allows. If you can afford name brand test instruments, by all means buy them; if not, select moderate priced equipment like Protek from a reputable dealer.
When buying a used oscilloscope, make sure it has been recently calibrated before you buy it; if you purchased it from a reputable test gear recycler, they will likely have specified that calibration was recently done and the equipment should have a tag with a calibration date shown. Since the oscilloscope is perhaps the most important piece of test gear on your electronics workbench, don’t skimp—buy the best you can afford. A quality scope
with relatively low duty cycle
of home use should last many years. If you are looking to purchase a used scope, be sure to look it over carefully. Make sure that all the controls move, and only make the purchase if the oscilloscope comes with a manual. We will discuss the oscilloscope operation and whether to buy a new or used in Chapter fifteen.
If you can afford it, your next purchase after the oscilloscope might be a function generator. A function generator generates waveforms that can be used to test and analyze electronic circuits. Signal generators can be as simple a sine-wave generator, and function generators can be as simple as a sine-, square-, and triangle-wave generator. Newer, more complex function generators might also produce complex waveforms generated by an internal computer. Depending upon your budget, you could purchase either a new or used function generator. You can locate good used function generators with many more years of useful service left in them from many test equipment resellers or calibrators (see the Appendix).
The third most important piece of test equipment for your electronics workshop might be the digital frequency counter. Frequency counters can be used for many applications around your new electronics test bench. Counters can be used to test transmitters, oscillators, clocks, pulser circuits, and so on. Frequency counters have dramatically dropped in price in the last few years. It is now possible to purchase a decent, new frequency counter for the price of a major-brand used counter. For a hundred dollars or so, you can buy a good frequency counter for your electronics workbench that will serve for most all the needed applications. See chapters 2 to 6 for discussions on the specifics of the different types of test equipment that you will need for your new electronics bench setup.
Tools and Stuff
In working with electronics, as with any other specific area of interest, you will need to acquire special set of tools, equipment, and test equipment in order to perform your work. These tools or equipment are broken down into essential or first or most important items, and then into a second level of equipment that you would want to acquire as time and money permit. These second-level tools and equipment would make your life easier but you may not be able to afford them initially. The primary tools or first-level tools might include a hammer, a set of screwdrivers, an end (wire) cutter, a pair of pliers (maybe needle-nose pliers), a soldering iron, and some fuses. Secondary, or level-two, tools might include right-angle pliers, hemostat, dental picks, magnetic screw starters, solder gun, and so on. In Chapter 12 we further discuss the most essential tools and supplies that you might want or need for your electronics workbench.
Another item that will help you round out your electronics workshop is a stock of common-value fuses. Fuses come in a variety of types, sizes, and shapes. For the most part, the AG fast blow
fuses are the most common types of fuses used for protecting circuitry. Historically, fuses came in little metal boxes with five fuses in them; today, you might find a package of two to five fuses in a blister pack. Try to select the most common values of fast blow
fuses, such as 1, 1½, 2, 3, 5, and 10 ampere fuses for electronic circuitry, and buy a box of each value. You may also want to duplicate these values in the slow blow
or delayed action fuses. Having these fuses available when you are servicing electronic equipment will save you much time and perhaps one less trip to the electronics supply store. Also, you could consider building the electronic fuse project described in Chapter 16. The electronic fuse project will allow you to temporarily substitute the electronic fuse for an actual fuse while you are troubleshooting a circuit that continuously blows fuses. You simply set the electronic fuse to the amperage or fuse value that was in the circuit, substitute the electronic fuse until you solve the problem, and then put the original fuse back into the circuit after you solve the problem.
You will want to acquire some electronic hardware items such as small screws, nuts, spade lugs, rubber foot chassis boxes, terminal strips, binding posts, and connectors. Screw sizes such as 2-56, 4-40, 8-32, and 10-32 are commonly used for electronic projects. For example, #6-32 screw size denotes a size 6 screw with 32 threads per inch. One of the best ways to store all small parts is to obtain some plastic storage boxes with see-through
plastic drawers. The plastic storage boxes are readily available and often on sale at major discount stores such as Wal-Mart. These storage systems are great for organizing small parts such as electronic hardware, fuses, jacks and plugs, spade lugs, and so on.
As you set up your electronics workbench, you will find that there are many little extra items that will make your life a bit easier. One of these little items is the mini jumper wires with alligator clips at both ends. This item is invaluable for connecting one portion of a circuit to another or connecting circuits to power supplies or batteries. These jumper leads are readily available will save you a lot of time; rather than having to make up special cables for every occasion, these general-purpose cables can readily connect new circuits to circuit additions.
If you discover that you really like to design and build new or prototype circuits, you will want to investigate the ProtoBoard or Solderless Breadboard. The ProtoBoard is a relatively new development for designing new circuits. This type of development system can consist of just the ProtoBoard, which is typically a 2¼ by 6½ inch plastic block with mini holes with recessed metal clips below the surface of the block that can be connected together via jumper wires. Integrated circuits and electronic components can be inserted into the ProtoBoard and be temporarily connected together to form a complete circuit. Proto-Boards are used to build new circuits that can be debugged on the fly,
that is, as the design develops. ProtoBoards make designing and building new circuits a simple and quick matter. Solderless Breadboards come in a number different types and sizes, and are often integrated with small power supplies or battery holders to permit them to be portable. Some advanced, self-contained ProtoBoard systems include a power supply and mini waveform generators and digital clock circuits. ProtoBoards can be transported from work to home to another hobbyist’s home to codesign a project. Prototypes and design as well as circuit fabrication are discussed in more detail in Chapter 14.
Reading Schematics
Before we move on to getting our hands on electronic circuits, you should get to know and identify electronic symbols and how to read an electronic schematic. Learning how to read a schematic will take some time and experience, but this chapter will give you an introduction and a place to start. Before you can read a schematic, you will have to be familiar with electronic symbols. Figure 1-9 shows some of the more common symbols used in electronics circuits. Look over the diagram carefully and familiarize yourself with the symbols. You will see some of the more common ones very often in your electronic schematic and electronic project diagrams. See Appendix I for an extended set of electronic symbols.
Figure 1-9. The most common electronic symbols.
The resistor is a device that resists the flow of charge. The unit of resistance is the ohm and is represented in schematics as k, which stands for kilohms. A listing of 10 k means 10,000 ohms. Sometimes, you will also see a capital M, which stands for Meg or megohm. A listing of 4.7 M means 4.7 million ohms. Variable resistors are sometimes called potentiometers, and they come in many different forms and shapes. The symbol for a variable resistor is a resistor with an arrow near the center, to show that its value can change. Resistors can be connected in series or parallel. If resistors are connected in series, their values add up. If resistors are connected in parallel, their values are divided. Resistors come in many different shapes and sizes as well as power ratings; see the components section in Chapter 9.
The capacitor is also another ubiquitous symbol in electronic circuits. Capacitors are devices that have metal plates separated by an insulator. They are used to temporarily store an electrical charge or to couple two circuits together. The symbol for a capacitor is two parallel plates with leads connected to each plate. The unit of capacitance is the farad, but its value is so large that the microfarad is the unit used for capacitance values. Microfarads are millionths of farads, and are often abbreviated as mf, MF, or μF. Capacitors are also often listed in picofarads or pf. A picofarad is sometimes called a micromicrofarads. It is 10–12 farad. Capacitors are often marked with a plus (+) or minus (−) terminal, which means that the capacitor is a polarized value capacitor. Capacitors with no markings are known as nonpolarized capacitors. Capacitors can be connected in series or parallel. When connected in series, their values are divided, but when connected in parallel, their values are added together.
Inductors are passive electronic components that stores energy in the form of magnetic fields, and are also used to form resonant circuits in radio equipment. In its simplest form, an inductor consists of a wire loop or coil. The inductance is directly proportional to the number of turns in the coil. Inductance also depends on the radius of the coil and on the type of material around which the coil is wound. The unit of inductance is the henry