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Practical Electronic Design
for Experimenters
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Practical Electronic Design
for Experimenters
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Contents
Introduction .................................................. . xi
7 Amplifier Design. • • . • • . . • . . • • . • • . . • . . • • . . • . . • . . • • . • • . . • . . • • . • • . . • 69
Amplifier Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Specifying Amplifiers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Understanding the Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
A Microphone Amplifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Designing with Op Amps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Primary Op Amp Application Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Differential Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Error Source Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Comparators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Power Amplifiers................................................ 83
Design Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Design Project 7.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Design Project 7.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Design Project 7 .3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Design Project 7 .4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
This book is for you experimenters and makers wheel? The result is lesser design time and greater
who want to design your own electronic circuits success at lower cost. Your design may not
and equipment. There are not too many books always be "leading-edge" but it will do the job.
like this. Most books tell you how electronic
devices work and provide some projects to learn
You Are the Target Audience
from. But now you have in your hands a book
that is actually going to show you how to design When writing this book, I had the following
your own electronic circuits and equipment. It is people in mind:
written in a way so that any of you who have a • Hobbyists, experimenters, DIYers, and
background in electronic fundamentals can create makers who want to create their own
a circuit or device to do something you want to do. equipment.
You don't have to be an engineer to design things.
• New engineers-graduates who are well
With the knowledge and procedures in versed in math, physics, and electronic
this book, you can create products for resale, fundamentals but have not yet learned to
implement scientific projects that need special apply that knowledge to creating products.
equipment, or produce circuits for your own
• Technicians who are knowledgeable in
DIY (do-it-yourself) idea. The book relies upon
electronics but have not designed.
the availability of popular integrated circuits and
the many finished modules and subassemblies. • Scientists like physicists, chemists,
Using existing products and legacy circuits geologists, and other users of electronic
eliminates most of the difficult circuit design. equipment who often need custom
In many cases, you can piece together existing noncommercial equipment but can learn to
circuits and modules to make a device with design their own.
minimal electronic design. However, some basic • Students who can supplement their
circuit design is usually necessary and hopefully, theoretical studies with practical design
this book will help with that. knowledge. Students in an introductory
The design approach in this book focuses on college design course or taking a design
making a working device using standard parts capstone course or culminating design
and circuits. The recommendations in each project course where the theory is applied to
chapter suggest that you use chips and circuits a specific circuit or device.
that have been used before. Why reinvent the It is likely that you are part of one those groups.
xl
xii Introduction
Now you can go on to the chapters on specific will give you practice in breadboarding
designs. If you do not have a good laboratory and/or using the simulation software.
power supply, you may want to go to Chapter 6 Some possible design solutions are given in
next and build your own power supply. Appendix B. Finally, as you go through the
You are on your own after that. You can go to book, you will discover a product or circuit
any other chapter as it fits your needs. that interests you. Start the design and
follow through.
Again, I urge you to build and test the
Design Projects given in each chapter. It Now, go design something.
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CHAPTER 1
This book covers design much like the stores, grocery stores, and pharmacies. Special
connect-the-pins approach. It offers an almost engineering notebooks containing grid paper
cookbook-like method for conceiving of a are great and useful but also expensive and not
product and making it. With literally thousands really necessary.
of different types of ICs out there, you need Do not skip this first step. You must keep
to be creative to put them together in one of notes and record details so that you know what
the almost infinite number of ways possible to works and what does not. You want to maintain
accomplish your design goal. Best of all, you all facts and figures, schematics, calculations, test
really do not have to be a graduate engineer to results, and debugging notes in one place so you
do it. But you do need to meet the prerequisites can reference them later if needed. And be sure
discussed elsewhere. to get into the habit of putting the date on each
Two key points to consider are: page.
• Know your chips. Get familiar with Many companies absolutely require engineers
the available ICs, dig out the details of to maintain a design notebook to document
those of interest, and get relevant data the progress and retain the experience and
sheets, app notes, etc. Keep track of new knowledge they acquire during the design.
chip introductions by monitoring the It also documents the activities in case the
semiconductor company Web sites and outcome is a patentable circuit, process, or
keeping up with industry magazines and product. Writing everything down will take
Web sites. some getting used to, and it may aggravate you
• Become software literate. Learn to code in a at first. Eventually you will discover how useful
popular language, and become proficient in the notebook is since we all tend to forget. You
writing programs for micros. The future is must document everything. This is especially
firmware. true in writing software code. Chances are your
design will include a microcontroller for which
The remainder of this book will take you
you will write some programs. Documenting this
down that path.
process is critical. If you or someone else needs
to revise or fix the software, you will appreciate
any explanations or other details you find there.
Get a Design Notebook Documenting can be aggravating, but get over
Before listing the design steps, you should it-before long you will grow to appreciate the
acquire a notebook that you will use to record-keeping process.
document your design. It will contain
statements of purpose, goals, features, benefits,
specifications, test results, identified problems, Get a Calculator
and other defining data. The notebook will also
When you design, you will be making
be used to contain your calculations, draw your
calculations. Most of the calculations are
block diagrams and schematics, and record test
simple formulas to solve or at worst, some
and measurement data. The design notebook
basic algebra. You may need to rearrange a
can be anything you are comfortable with. A
formula to solve for a different variable, for
standard-size spiral bound school notebook is a
example. For these calculations you need a
good choice. They are available in most big box
scientific calculator. The calculator should
stores like Walmart and Target, office supply
include scientific notation, trigonometry
Chapter 1 • Introduction to Electronic Design 3
• Definition
8 Write Specifications
• Detail design
• Simulation (optional)
• Prototype Get
Details
• Testing
• Packaging
• Use
Get
10 MFG
Definition Stage Input
Id tj fjj 81 The most commonly used electronic circuit building blocks and what each does
Id' a8' The most commonly used electronic circuit building blocks and what each does (Continued)
power consumption. Also consider ease of you may need to meet some required set
use, maintenance, and potential repair. The of standards mandated by law. Examples
end product should be simple to operate are ac-powered devices that may have to be
with minimal training or instruction. tested by the Underwriters Laboratories
9. Consider required testing and certification. (UL) or the Federal Communications
If you are designing a product for resale, Commission (FCC).
Chapter 1 • Introduction to Electronic Design 7
1o. Will the product be manufactured? If this is a capacitor values, any read numbers
one-off product, skip this step. If the product or part numbers on the ICs, and
will be made in volume, be sure to involve the transistors. Record all this on the
manufacturing people in evaluating the design schematic diagram.
and getting their input regarding steps to g. Redraw the schematic diagram and part
make the device from initial PCB construction numbers and values. NOTE: In many
through final testing and packaging. products, the labels on the I Cs will
11. Record all of this information in your be omitted to prevent someone from
notebook. identifying the part and copying the
circuit. If that is the case, maybe later
12. Next, you should look to see if what you
you can deduce what it is.
defined is already a product available for
sale. Maybe you won't have to design it if h. Given your copied design, consider
you can purchase a ready-made version. Do whether you could duplicate this item.
an extensive internet search. Use different If you can, you can adopt the design
product names or descriptions to be sure for your own version. If you do not
you will locate something similar. If you believe that you can duplicate it, just
find something similar, acquire as much reassemble the product and use it. Then
information as you can, and compare its move on to another project.
features and specs to your definition. Buy 14. If no commercial product turns up to buy,
the product if you can afford it. press on with the design.
13. Reverse engineer the product. Take it apart,
being careful not to damage anything. Do Detail Design Stage
the following:
This is where you fill in the boxes in your block
a. Take photos along the way. diagram with specific circuits, modules., or other
b. Identify all of the major subassemblies units. Think of the various circuits available and
and larger components, and document how you can use them as building blocks. From
any wiring between these sections. your searches you should have identified the circuits
c. Identify the power source like the ac or ICs you want to use. Identify specific circuits
line or batteries and the related power where you can. Search for specific ICs that do what
supply. you need. You should be able to determine that
you need an amplifier, a :filtei; a digital counter,
d. If PCBs are involved, remove them, but
LCD display, or whatever. You may do some rough
record any interconnections by way of
partitioning at this point as you identify different
connectors or wiring.
parts of the design. For example, you may have an
e. Develop the schematic diagram from analog signal or linear segment, a digital segment,
the PC board. Identify how the copper and a power supply segment. Then, for the first
traces on the PCB connect the various time, try to draw a schematic diagram of the design.
components. Your initial schematic Next you will choose components to match
diagram will be messy and crude, but you your circuit specifications. You will be selecting
can redraw it later in a more useful way. ICs, diodes, transistors, capacitors, resistors,
f. Identify the individual components. potentiometers, transformers, and a mix of
Read the resistor color codes, read other parts. You should have catalogs on
8 Practical Electronic Design for Experimenters
still be able to get it elsewhere. Chapter 14 product by using standard textbook theory
gives you some recommendations. and procedures. There are multiple textbooks
1o. A microcontroller design is not always the to help you do this. The procedures are well
best approach. Most products today are based known and generally proven. They are taught in
upon a central embedded controller. These college. This approach does not use cookbook
microcontroller units (MCUs), or micros as recipes but offers the theory with examples,
I refer to them here, are flexible and cheap, then tests you with end-of-chapter problems.
but they require software and programming The theory is given, but its interpretation
in addition to the electronic interface design. and its implementation are left to you. This
Sometimes a simple hardware design is the book generally uses this approach, but it is
fastest and cheapest solution. supplemented with a bit of experience that yields
some step-by-step procedures that save time.
11. Focus your budget on good test equipment
and prototyping equipment. You cannot
really design without testing and measuring Empirical Design
equipment. So, plan to set aside a budget
This approach is design by experimentation.
for a good multimeter, oscilloscope, and
You can also call it the cut-and-try method. You
breadboarding gear.
essentially start with something you know, then
12. Learn and have fun. Experiment. Screw up. observe the result. If it is not what your goal is,
Fail. Learn what works and what does not. you experiment. You change or add something,
Then eventually achieve success. observe the outcome, then change again if the
end result does not tum out as you want. You
WARNING! go back and learn some more. You keep on
In designing commercial products, some circuits learning, testing, experimenting until you get
and methods may really be new and patentable. what you want. It sounds crazy, but it works,
These circuits or methods become valuable especially for those with some experience in
intellectual property (IP) to your employer. Such
IP may give some company competitive benefits. the subject. After a while you get to know what
Or the company could license the design to works and what does not.
generate royalty income. This is especially true
of IC designs, but it could apply to some other
arrangement. Just be sure to document everything Intuitive Design
in your notebook in case it comes up.
This is an approach that is based upon years
of acquiring knowledge and experience that in
tum give you the intuition to create something
Types of Design new. Your design is based upon your intuition
When designing any electronic circuit or without supporting facts. You go with what you
product, you will discover that there are lots of know and believe to be true. Or as they say, you
ways to do it. My own view of this is that there go with your gut.
are three basic design approaches. Here is a After years of design experience, I have come
summary of each. to believe that a person inherits some of each
approach. You start with the textbook approach,
Textbook Design learn more as you experiment with the empirical
approach, then finally with sufficient knowledge
You could also call this the traditional approach. and experience you go with the intuitive
This is the process of designing a circuit or approach.
Chapter 1 • Introduction to Electronic Design 11
8. No specifications other than those features I also needed an audio amplifier to operate
described in step 3 were written since the headphones.
they are not applicable to noncommercial A second method of detection that I call
devices. variable tone uses an oscillator whose frequency
9. No testing or certification is required for is changed by being close to a metal object. It is a
personal products. simple circuit, and it seems cheap and easy to try. I
suspect that the heterodyne method is much better.
1 O. The product will not be manufactured in
quantity. Figure 1.4 shows the simple circuit. A
555 timer IC is used as an oscillator with a
1 1. I did write down all the details in my
tuned RLC circuit setting the frequency. This
notebook.
frequency is in the audio range so you can hear
12. A search for a commercial product did it. With the values shown in the figure, the
occur. There are many. From low-cost frequency computes to 1073 Hz.
hobby models for less than $100 to military-
The big design obstacle is the inductance that
grade units for finding mines costing
not only sets the frequency but also serves as the
thousands of dollars. No commercial
search coil. The desired inductance is 10 mH.
product was purchased.
The search coil is many turns of copper wire
13. No reverse engineering took place. whose diameter is in the 4- to 10-inch-diameter
14. The design process will go on. range. Approximately 140 to 150 turns of wire
Chapter 1 • Introduction to Electronic Design 13
+V +V
4 8 lOµF
3
555 ~./lsn
_!jspeaker
1
J2.2µF
n
with this to make it work. I ended up with 140 v
T50pF
turns of #22 wire on a 6-inch-diameter form.
I never did know the exact inductance, but it was
lOmH
Search
= 9V = = 5.1 V
Normally you will just hear the audio tone. Q!l!tjJj A final circuit diagram of the metal
detector.
If the coil is passed over metal, it affects the
inductance of the coil, usually increasing its 10 mH is the target, with about 140 turns of wire
value and thereby lowering the audio tone. six inches in diameter. I also changed the audio
A design using the heterodyne method amplifier. The final circuit is shown in Fig. 1.5.
was hard to come by. I found two references The biggest hassle is the coil, and it required
illustrating this approach. One of them uses a great deal of testing to zero in on an audio
two complementary metal oxide semiconductor frequency. That frequency is not particularly
(CMOS) oscillators operating in the 160 kHz critical, but it must be something you can hear.
range. (Low Power Metal Detector, from If the 300-kHz design is used, the search coil
Encyclopedia of Electronic Circuits, Rudolf F. can be much smaller. The target inductance is
Graf, Tab Books, 1985.) 330 µH. A suggested search coil size is 40 turns
The circuit uses a CMOS XOR IC to create about 7.5 cm in diameter.
the two oscillators, a mixer and an audio The main circuit modifications were the
amplifier. Another similar design used the same replacement of the no-longer-available 4030 IC
CD4030 IC, which is no longer available. This with a 74HC86. I selected the design using
design (Simple Metal Detector Circuit with 160 kHz oscillators. One of the oscillators called
CD4030, HYPERLINK "http://www.next.gr" for a variable inductor that I could not find.
www.next.gr) operated at a frequency of I used a fixed 10-mH inductor and added a
300 kHz. It used a standard 330 µH inductor for 100 pF variable capacitor so the frequency
the fixed frequency oscillator. could be varied over a narrow range.
Again, the main design problem is getting the I used the popular LM386 amplifier for the
search coil right. An inductance value of speaker or headphones.
14 Practical Electronic Design for Experimenters
After the design, I skipped the simulation and • Build a kit. You do not have to design
went right to the prototype. I spent many hours anything. You will simply build the kit
tinkering with it, which is typical of some designs. as detailed in the instructions. It will get
The oscilloscope was useful in determining the you familiar with the components, and
frequency of the oscillators. I also tested the you will learn some soldering and other
circuit on several pieces of metal such as a coil, related skills. A small robot kit is a good
a ring, and a small piece of aluminum I had. It choice. Some kit sources are given in
does work; as the metal is sensed a tone change Chap. 2.
occurs to signal the find. The goal of achieving a • Build an existing design. Locate a circuit
detecting range of 10 cm or more seems remote, for a product or device you are interested
however. More testing is needed. in and just copy and build it. Again, there
As for power, I used a 9-V battery. All the is no design involved. However, you will
circuitry seems to be OK with that except the become comfortable with breadboarding
74HC86 IC. I used a 5.1-V zener diode to reduce and prototyping and some testing and
the voltage for the IC to 5 V. troubleshooting. Look online and in
I won't bore you with the packaging other than magazines for circuits to copy and build.
to say I left the circuit wired on breadboarding Each of the design chapters contain some
socket and put the whole thing in a box. useful circuits you can easily build and use in
future projects.
The metal detector did work after much
tinkering. Determining the actual value of the • Initiate a so-called system design. A
coil inductance was an issue. I solved it using system design is a higher-level approach
a measurement method described in Chap. 4. than circuit design. It involves putting
Inductance increases with the number of turns together multiple existing parts and
of wire. If measurement determines that the pieces, including software, to create a
inductance is too low, add more turns of wire working system. Some examples are:
and measure again. If your inductance is too radio/controlled airplane or drone, audio
high, reduce the number of turns of wire. Repeat system, TV streaming, video doorbell,
until you get close to your target value. Once home security system, or something PC
I got close to 10 mH, the circuit worked. The controlled. No circuit design is involved,
device does detect metal, but it did not live up to but you will work at the block diagram
its goal of picking up metal objects 10 to 20 cm level, following signal flow between items,
below ground level. This is typical of many and you will make multiple devices all
projects. More experimenting is needed. work together.
The idea here is to start small and easy to
ensure some success that will give you the
An Alternative Beginning
confidence to go on. Practice on larger and
If you are new to electronics, and the metal larger projects until you feel ready to try some
detector example seems too much of a challenge, design. A small robot kit today, a Battlebot
here are several alternatives. tomorrow.
CHAPTER 2
Design Resources
As you design, you will need a lot of additional Some free online ebooks on electronics
information. And there is a boatload of it out are available. These are mainly addressed to
there for your use. You just need to know what college instructors and professors, and they
it is and where to get it. The internet will be the cover the fundamentals. It is good to have some
major source of it, but there are other sources theory books on hand when you need to look
like books, catalogs, and magazines. You will something up. Try at these sites:
certainly find much of the needed information Open Educational Resources (OER)
on your own with internet searches. This chapter OERCommons.org or Merlot.org
summarizes some of these sources and shows
http://www.freebookcentre.net/Electronics/
how to get them.
Engineering-Books-Online.html
https://ebookpdf.com/basic-electronics-books
Books https://easyengineering.net/power-
electronics-books/
It is always good to keep a few good reference
books on hand to use as needed to understand https://www.allaboutcircuits.com/textbook/
a component or circuit, check on related theory, http://www2/mvcc.edu/users/faculty/j:fiore/
or solve a problem. You may already have a freebooks.html
library of books you use. Some recommended
suggestions for books that are useful when
designing are given in App. A. Sources of Catalogs,
If you can't find what you need, search the Components, and Equipment
internet for other books. You can search on the
You will be buying parts and equipment as
publisher's Web sites or do a general search.
you design. There are multiple sources for
Some publishers to consider follow:
what you need. It is extremely helpful to have
• Elsevier/Newnes a listing of parts and equipment available and
• Maker Media where to get it. The following is a list of parts
• McGraw-Hill sources you can use as reference in selecting
parts and equipment. Go to their Web sites
• Pearson/Prentice Hall
to select parts. Some of these sources still
• Wiley offer print catalogs that are helpful to have
Amazon is a good place to search. They are the on hand. Most distributors have discontinued
largest bookseller in the world these days. Barnes print catalogs because of their size and cost
and Noble also has a good site to search. to print and update. Everything is online, so
15
16 Practical Electronic Design for Experimenters
These are the only Web sites I have discovered reference book. It is a good review for those of
so far. I keep finding new ones as I search for you who have learned it before. It also makes a
information. You should do the same. And don't good first course if you are just beginning.
forget the Web sites of the magazines mentioned A good source of math instruction if you
earlier. All are useful. are a bit rusty or just never learned it is Khan
Academy. It offers online instruction in all levels
of math from grade school level to university
Educational Sources graduate level: algebra, trig, calculus, statistics,
As you design, you are going to want to and others. They also offer some online courses
learn new subjects and procedures. All of the in physics and electrical engineering you may
resources given earlier are learning sources, but wish to explore. And it's free.
there are some Web sites that are designed for YouTube videos are another good source
more formal instruction. For example, there are of the basics. There is so much out there it is
many educational videos on YouTube and other hard to describe. Just search on what you need
sites. The way to find these is to do your usual to know. Recently, a friend of mine needed to
internet search but include the terms tutorial, repair or replace the headliner in his 1997 Dodge
learning, instruction, or education along with the vehicle. A search turned up five videos on that
subject. specific topic. All amateurish but collectively
For formal college-level online courses go to useful. I suspect most of you have already
the following Web sites: discovered this resource. Something to try when
all else fails.
coursera.org
edx.org
Udemy.com. Searches
They all cover electronics, software, and I am sure you already do searches for
programming along with many other related information and answers to your questions,
topics. I have used these multiple times and whatever the subject. There are lots of electronic
recommend them if you just need the formal and design materials out there. You can search
instruction. They work. on topics like the following:
• Part number
• Type of circuit
Back to Basics
• Kits
If you need to review electronic fundamentals
• How to design a .. ... .
before you do a deep dive into this book,
I recommended the video course titled • How to test a .... .
Understanding Modern Electronics by Richard Anyway, you know what to do. Print out what
Wolfson. It is published by The Great Courses, you find so you can have a hard copy with you
Chantilly, VA. It features 24 video lectures and a on the work bench.
CHAPTER 3
After you design something, you will need mathematical model of the circuit internally.
to build a prototype of it. Prototyping is the Then you can run the software model to see if
process of creating a real physical version of your circuit works. Most simulators also have
your circuit or device so that you can see if it virtual instruments (scope, meters, etc.} to use
works. It is the critical part of the design process. in making measurements. Then, depending on
There are also instances when you will discover a the outcome of the simulation, you can make
circuit you like and may be able to use. Your first changes until you get the circuit to perform as
step of the design would be to build the circuit you wish. Figure 3.1 gives a glimpse of National
and evaluate it based upon your needs. Then you Instruments' Multisim.
can modify it to fit your specifications. In any There are literally dozens of such simulators.
case, you must build a prototype. It is the only Many are free and others cost a small fortune.
real way to validate its operation. Some common The following list shows just a few of the
prototyping techniques are described in this simulators I have discovered and used. Like any
chapter. software, simulators will take up a good deal of
There is also another way to build a your time while learning how to use them. My
prototype. Use software simulation. Circuit recommendation is to research the following
simulation software lets you build your design links, download a free trial version of one, and
on your computer and test it. It is not a give it a try. Start with some simple circuits to
necessary step in design, but it is a handy tool get the feel for it, then move on to the more
to use before you commit to a full hardware complex circuits as you gain some experience
prototype. and competence with the program. Some
Many of you may already be using the simulators I have discovered follow.
techniques covered here. In that case, you can • Circuitlab
just skip this chapter and move on. • LTSpice (Linear Technologies/Analog
Devices}
• Micro-Cap
Circuit Simulation
• Multisim (National Instruments}
Circuit simulation is the process of building a
• TINA (Texas Instruments}
mathematical model of your circuit on a PC.
Special software does this for you. The most Some others to check out are
common approach today is that the software lets • 123D Circuits
you enter your circuit as a schematic diagram.
• CircuitLogix
Using predesignated component symbols and
interconnecting them, the software builds a • Circuit Simulator
19
20 Practical Electronic Design for Experimenters
Rcflsmfn Vee
11&
PR2
2
Rdchsmin UtPR3
~
lkQ UT
JST OUT
-
5
Dchs DIS OUT
1N4148
Od~
-
T IU
1N4148 Ctll
3 6
Rdcod) P~t
Cctf 0
Ct
r·~
Potentiometer RdcadJ ad3usts the duty cycle
with slight effect on frequency.
mI I: ¥5 •
I A glimpse of the screen of National Instruments' Multisim showing a simulated circuit.
(Ort:uit courtesy National lnstruments'Website www.multisim.com)
and flip flops. The real parts simulations will In addition, use the simulator for some of the
produce a more accurate simulation. suggested circuits, then test the software using
• Tech support. Choose a simulator that has the design projects in each chapter to verify the
sufficient documentation you can learn outcome. Once you find out if the circuit works,
from. A desirable feature is online chat or you can build one and test it. The more you
telephone help to answer your questions and practice with the simulator, the better you will
provide additional information. get at it.
Recommendation
\.
The whole circuit simulation process is complex
and difficult to describe in a book chapter. I urge Q L\ @JQ Several circuit prototypes on the
you to get a simulator and try it out. You must breadboard. Messy as usual, but they
experience it for yourself and learn bow to use it. all work.
22 Practical Electronic Design for Experimenters
Figure 3.3 shows a more detailed layout. For to five leads or wires together. The long string of
each five-hole group, a pressure connector on the holes nmning along the sides of the boards are
backside of the socket electrically connects up buses or power rails used to connect the circuits
to the power supply voltage and ground.
Each Square These Five These breadboards provide a fast and easy
is a Hole for a Holes Connected way to put a circuit together with standard
Component Lead. Together.
components with leads. Newer surface-mount
-+ -+ components do not have wire leads, so they
AB abcdc fghij AB
1 1 r,
cannot be used with these sockets directly,
I --,. 0
5
00 00 o~
s
although some special adapters are available to
allow surface-mount parts to be used.
Adjacent
Groups Not
I 10
. 00 OOO
00 OOO
10
These prototyping sockets are available in
multiple sizes to fit your project. The most
common size is the 840-terminal board that
Connected.
I 20
25
20
25
experimentation, it is handy to use some of the
smaller boards and just build one circuit on it.
Don't tear it down as you may need that circuit
IAB
-+
30
abcde fghij
30
AB
-+
again in another project, and you won't have to
build it, test it, or troubleshoot it again.
Figure 3.4a shows a schematic diagram of an
...
"I _ All Holes in B Column I op amp test circuit. Figure 3.4b shows the IC pin
Connected Together. numbering. The typical wiring details of an IC
All Holes in A Column _ op amp with resistors connected to a +V and -V
Connected Tugether. power supplies.
(a)
There are no particular rules to translate
your schematic diagram into actual wiring. The
only common format is to connect the positive
lead of the power supply to the + bus and the
negative lead of the power supply to the - bus.
This lets circuits on any part of the socket tap
into power and ground where needed.
The ICs straddle the center line. A good
beginning point is to plug in any ICs first then
connect the de power and ground wires. Then
add the other wiring. The preferred wire is
insulated #22 gauge solid copper. Buy a roll of
(b) it. Special wiring jumpers for these sockets are
Q!!@Jf 1 (a) A common breadboard layout. also available. These are precut to several lengths
(b) The most popular breadboard and have connectors on each end to make
size.
Chapter 3 • Simulation and Prototyping 23
I 00 00 0
;t ...
I
\:> l
- I-
I/°(})
I
i..-OutpuL_
Building circuits on breadboarding sockets is OK
for de and low-frequency projects. However, if you
are making higher frequency circuits, you could
introduce too much stray, distributed, or parasitic
inductance and capacitance and create a circuit
..... -J rt ..... that does not perform well. It could oscillate,
I
"<I ".CJ
v ..... -
have a limited frequency response, do weird
11 I I a'-' ~ \ I
-...... :..- things, or just not work. At higher frequencies,
~
"'
I I ~ \
.....
...,.!-'
I'"' ·~
~ 1 I
-- say those beyond about 1 MHz, the component
leads and wires become significant inductors.
?_ """""
- ..... r ... ' I
f \..
--
~
,__
The capacitance between component leads or
the capacitance between the connectors in the
- ..... ,__
--
GND
--
--
breadboarding socket may create a circuit that you
did not intend. If you suspect this is happening,
then there are several things you can do.
IAB
-+
IAB
-+
First, shorten all component leads as much as
is practical, and shorten all wires. You may even
want to try another layout on the socket, putting
the components closer together. If that does not
help, you may need to use some other prototyping
method as discussed elsewhere in this chapter.
GND
(c)
to match up with common IC lead spacing. that it should perform better and look more like
The idea is to put the component leads through a finished project.
the holes, bend the leads over, and make the There are several kinds of perf board
circuit interconnections with solder on the that provide an even more finished look to a
back of the board. You can use the component prototype. One type has copper wiring patterns
leads themselves or use wires as necessary to on one side that you can use to make the
make the connections. Connections should be interconnections. (See Fig. 3.6.) These boards
soldered. For higher frequency circuits, keep the come in different sizes and have different solder
components close together and the leads short pad arrangements. You still put the component
for best results. Figure 3.Sb shows an example. leads through the holes. but you solder the leads
This method of breadboarding is a little to the copper pads. You have to use the pads
neater and closer to what a printed circuit that are available to make the links between
board (PCB) layout would look like. It is a bit the different parts. In some cases, you may
more difficult to build than using a prototyping have to add a wire here or there to make the
socket. And it is also a bit more difficult to connections. The result is a very organized and
troubleshoot and to make changes. The upside is neat package. For one time designs this could be
your finished project.
(c)
......................
... ...........................
.......... .. ... ... ....
........ . .. . . . . .. . . . . . . .
........................................... ........... . . .
(a) .........................
.........................
························
................. .........
................
························
........ .... ........... ... ........
·················
.........................
. ........ .........
.............. .. ...······... ....
......................... .......
.......................
·······················
................... ...................................................
......
.... .....................
........... .....
.....................
•••• • • ••••• •••••• • •••• OI
(a)
.................................
............ ...... .... ...
~
\ .. ············
.. (b)
Dead Bug Method one side. Then build a simple circuit yourself.
Make your decision from there.
One alternative way to build prototypes is to
use the so-called dead bug method. It uses an
unetched PCB with full copper cladding on Working with Surface-Mount
one side. This becomes your base and common
ground for the circuit. If your design uses an IC,
Components
you lay it leads-up with the top of the IC on the In general experimenting and prototyping, you
copper. You will then bend the IC ground lead will use ICs in the standard dual in-line packages
over and solder it to the copper. If the circuit (DIP). They plug right into breadboarding
calls for other pins to be grounded, bend them sockets and are larger and easier to handle than
over and solder them to the copper. The other the surface-mount devices (SMD) that are used
IC pins you will solder to other components. in most new electronic equipment. Most of the
Resistors, capacitors, and diodes are simply older parts still available today are in a DIP. Use
soldered to the IC pins and/or each other. The these whenever you can as they are less expensive
component leads are sturdy enough to support and work well with breadboarding sockets.
one another in free space above the copper base. There may be times when you want to use a
The result is a self-supporting messy circuit. particular IC, but it is only available in a surface-
Wires are added to the circuit as needed for mount package. These are difficult to work with
external power and signals. but there are helpful prototyping accessories you
I do not recommend this method. It is hard can buy. An example is a small PCB to which
to follow or trace on a schematic diagram, and you can solder the IC. This small board has pins
it is difficult to solder all the parts together. that plug into a breadboarding socket. These
I do admit that the entire circuit is out in the adapter boards are made by SchmartBOARD
open and that makes it easy to connect to test and Capital Advanced Technologies. Keep them
equipment and other external devices. Some in mind if you ever need one. Most of the newer
designers swear by this approach. It is the best ICs come only in surface-mount packages. You
way to test high-frequency circuits. Apparently, will definitely have to deal with them at some
this method is good up to 1 GHz if you keep the time.
leads short to minimize stray inductance and
capacitance.
Components
Some who use this technique have found a
way to separate segments of the copper so that To test the circuits and products you plan to
signal leads and other nonground connections design, you will need the components to build
can be made. You can actually score the copper them. You will choose these parts yourself
with a knife until you create an insulating space according to the design. This book suggests and
between copper sections. You can also cut copper recommends many of the parts. See Chap. 14.
strips with your knife and peel the copper off. In some of the projects, specific parts like ICs
Other not-so-elegant mechanical methods can will be given. You will need to buy these parts as
be used to create separate islands for multiple needed from the sources listed in Chap. 2.
connections, such as using a Dremel tool. The best preparation is to have on hand some
If you want to try it out, get a blank piece of of the most common parts you will always need
PCB, such as FR4 with full copper cladding on like resistors and capacitors. One good approach
26 Practical Electronic Design for Experimenters
is to buy available sets or kits of resistors and small table is all you usually need. You can set up
capacitors that include multiple pieces of all the your test equipment and other stuff and leave it
most common values. It is maddening and off- there between work sessions.
putting not to have a specific value of a resistor
or capacitor when you are ready to build the
circuit. These kits are relatively inexpensive and Summarizing
a good value. You can also get kits of transistors, A general recommendation is to use the flexible
diodes, and ICs if you want to go all out. Check
and convenient breadboarding sockets for your
with the distributors to see what is available. initial prototyping efforts as you can build the
With most common parts on hand, your orders circuit fast and make changes and corrections
will only be for the special parts required.
quickly. You should keep several of these sockets
in different sizes on hand. Also get some perf
boards to build your finished circuits. There are
One Good Prototyping instances where you may need a socket for a new
Practice project but none are available. That means you
When building a multicircuit project it is may have to tear down an existing prototype to
desirable to keep each circuit separate from free up the socket. This is usually a big mistake.
the others. Put each circuit on a separate small You never know when you are going to need
breadboarding sock.et, perf board, or dead bug that circuit again, so it is a good idea to keep
board. In many projects, you may be using one previously used circuits for later applications.
of the small microcomputer boards like the As you perfect the circuit, you can move from
Arduino. Keep it separate. If you are using a the breadboarding socket to a perf board for a
reference design kit that some IC manufacturers more finished appearance. As a next step, take
sell, keep it separate, too. Then you can wire a look at what is available in a catalog or online
all the individual boards and pieces together to and search for these sockets and boards to see
make the final product. what may fit your projects.
This separation-of-circuits method makes
design, testing, and troubleshooting faster and
easier. Design and test each circuit separately
A Word About Tools
without the clutter of multiple circuits all on one If you have done any electronics work before,
breadboarding socket or perf board. Later, when you may already have the necessary tools for
you have proved that everything works, you can prototyping, kit building, or repair. If not, here
always repackage it. is a short list of the minimum tool inventory
needed for most projects.
• Needle-nose pliers
A Workbench • Standard pliers
It is difficult to work on electronic projects without • Side cutters
the proper space. You cannot always commandeer
• Wire stripper
the kitchen or dining tables for your designs. If
possible, try to set up a dedicated bench where • Sharp knife
you can do your design and prototyping. Use the • Several sizes of both standard and Philips
basement, garage, or a comer of a bedroom. A screwdrivers
Chapter 3 • Simulation and Prototyping 27
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