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'[EE:] How do you create and understand circuits? ('
2007\01\28@072316 by Lindy Mayfield

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face
This is a serious question.  How do you "understand" how a circuit works and how do you create with your imagination a new one?

I've been a programmer most of my life.  But since I was a teenager I've been reading electronics books, ones like Forrest Mimms and others, and I've always been fascinated with electronics.  

As a programmer I need to understand how the computer works, to some extent, but to create a program I need to know the basics like what the verbs are, how to control the flow, input/output, etc.  And then after a while and with practice I can do more and more complex programs.

Well, I've read many books many times on electronics and I think I understand what the components do, but I just cannot figure out how to truly understand circuits.

How do you do it?  At first I tried to imagine water flowing from the power supply through the wires and components going from + to - but that didn't get me very far.

I loved Pic because it was mostly programming, but I always got thrown by _how_ the components of a circuit board were put together.  I do admit I lack some of the math that is necessary to get the correct values of components, but I think that can come after I understand.

Why can't I "get" it?  I'm not stupid, just I don't think I'm looking at things the correct way.

I've been on the Piclist for at least 3 or more years now so it's not like I'm not trying.

Any helpful advice for people like me I will take to heart.

Kind regards,
Lindy

2007\01\28@080013 by Vasile Surducan

face picon face
On 1/28/07, Lindy Mayfield <spam_OUTlindy.mayfieldTakeThisOuTspamssf.sas.com> wrote:
> This is a serious question.  How do you "understand" how a circuit works and how do you create with your imagination a new one?

You need what is called experience. A couple of years you have to
reproduce others projects and understand how it works. The next step
is reverse engineering
of good designs starting from PCB and aquiring the schematic.
The next step is modifying such schematics for better results.
The last step is creating your own designs.
In the mean time, reading everything is published on your favourite
area of interest is must.
You have an advantage being programmer (the advantage is your logic,
assuming all programmers have good logic) but usually software
programmers have serious leackage in basic of electronics and they
start without having the smallest ideea about how really a transistor
works.

So, for you will be much easy.

success,
Vasile

2007\01\28@081552 by Jinx

face picon face
> This is a serious question.  How do you "understand" how a circuit
> works and how do you create with your imagination a new one ?

It really really helps if you've got an end product as the goal. Also
a good general knowledge of what devices are out there and what's
probably appropriate to use to reach that goal. Experience and practice
are musts, IMHO. Have a look at magazine articles and the 'How It
Works' panel to see how they accomplished various circuit tasks

For example

http://www.siliconchip.com.au/cms/A_30551/article.html

is a good mix of analogue, digital and PIC, and is well documented

>From a personal perspective, not having had any formal electronics
training, I think the initial idea is more important than the understanding.
That can come later when you try to get the different parts of the
circuit working with selected components

We here would generally be working with components that obey
a few simple rules, so the limits of what you can do with those
components are not too difficult to stay within

2007\01\28@081825 by Paul Anderson

face picon face
On 1/28/07, Lindy Mayfield <.....lindy.mayfieldKILLspamspam@spam@ssf.sas.com> wrote:
> This is a serious question.  How do you "understand" how a circuit works and how do you create with your imagination a new one?
>
>
I'm still learning myself, though I'm further along.  I found my
understanding took a big leap after getting my ham radio license, it
covers a great deal of basic electronics.  I find I've become familiar
with certain structures, and look for them in schematics.  A voltage
divider using resistors is classic, and shows up all over the place.
Know ohm's law, E=IR.  Remember that transistors are *current*
devices, and need a resistor on either the collector or emitter side
to work.

I've also had good luck with application notes.
Maxim(http://www.maxim-ic.com ) has a HUGE collection of application
notes covering all manner of electronics design subjects.  Pick up a
copy of the ARRL Handbook, and build some stuff.  Doesn't matter if it
doesn't work, you'll be able to build it.  Build an audio oscillator
with a transistor, some resistors and capacitors.  Then scare all your
friends who needed a 555 to do the same thing:P




--
Paul Anderson
VE3HOP
wackyvorlonspamKILLspamgmail.com
http://www.oldschoolhacker.com
"May the electromotive force be with you."

2007\01\28@100041 by Robert A LaBudde

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face
At 07:23 AM 1/28/2007, Lindy wrote:
>This is a serious question.  How do you "understand" how a circuit works
>and how do you create with your imagination a new one?
><snip>

I have been in the same boat. My brother is an electrical engineer, and I'm
a chemist. He is 3 years older than me, and sibling rivalry kept our
expertise areas separated. I've spent 30 years trying to learn electronics
after I "grew up", but will never match his knowledge.

Some suggestions:

1. Analog electronics is based on "equivalent circuits", or simple models
as to how each component works. To understand analog circuits, you must
first completely master the theory of passive circuits (DC and AC circuits
involving only resistors, capacitors and inductors). This includes Ohm's
law, Kirchoff's laws, etc. Then you must accumulate knowledge of the key
equivalent circuits for more complex devices (diodes, transistors, etc.).
With these equations and models you can analyze most simple analog circuits.

2. Digital electronics is much easier for someone like you to get into, as
the states are logic-based, and programming is an extension of logic. I
don't think you would have much trouble picking up simple digital circuit
analysis.

3. Parts of electronics that involve electromagnetics (RF, radio,
magnetism, etc.) are difficult to understand without special courses and
considerable mathematics and experience.

4. Good books for learning analog electronics are 1) a college first year
EE text obtained locally; 2) Malvino's books on semiconductors and digital
electronics; 3) The Art of Electronics after you have mastered the others.

5. Opamps are easy to learn analog electronic devices, so long as you stay
from the performance envelope.

6. You should also obtain some test equipment (oscilloscope, multimeter,
frequency generator) and do some breadboarding experiments on simple
electronic circuits. A good way to start is to measurement the response to
different inputs, and try to validate the device specifications.

7. To understand the basics, you will need a solid grasp of algebra and
trigonometry. To understand AC circuits fully, you will need elementary
calculus (derivative and integral). To understand E & M, you will need
multivariate calculus (at least Gauss' theorem). There are workarounds
(e.g.,  lines of force) to some of this, but it will leave you still
searching for answers. Math is next to impossible to pick up outside of a
school environment.

In summary, if you're not young anymore, concentrate your learning on
passive circuit analysis, opamps and digital electronics. That will keep
you occupied for a couple of decades anyway.

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: .....ralKILLspamspam.....lcfltd.com
Least Cost Formulations, Ltd.            URL: http://lcfltd.com/
824 Timberlake Drive                     Tel: 757-467-0954
Virginia Beach, VA 23464-3239            Fax: 757-467-2947

"Vere scire est per causas scire"
================================================================

2007\01\28@100507 by Lindy Mayfield

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face
Everyone has given me good advice, which I will follow.  But what I don't understand is how you -- I don't know the words I'm looking for -- how you read a circuit.  If it were a program, I'd could start at the beginning and follow the flow keeping track of variables, like a debugger does.

I think I'm trying to do that with circuits and sort of my question is, am I doing this right, or is there a proper way that I haven't figured out yet?  Do you start at + and work your way to - ?

I read every single "how it works" I find, and I understand a bit, but I don't quit get it in a way where I could look at a circuit and tell what it does.

I have a theory though. And please let me know if it is in the ball park.  Certain components and groups of components we know do various things.  Like little modules (or subroutines or function libraries).  And that when designing something you know which of these modules to put where to do what.

My landlady said I could put a floor of sorts up in the attic, and then I can put a desk up there and start playing with electronics again.  I had to stop for about 2 years now because of the cats.  

I just think I'm not looking at the big picture correctly.

Lindy


{Original Message removed}

2007\01\28@100659 by Lindy Mayfield

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I have the ARRL Handbook. Very nice.  And The Art of Electronics. And a slew of other books.

-----Original Message-----
From: EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu [piclist-bouncesspamspam_OUTmit.edu] On Behalf Of Paul Anderson
Sent: Sunday, January 28, 2007 3:18 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE:] How do you create and understand circuits? (i.e. why am iso stoopid)

On 1/28/07, Lindy Mayfield <@spam@lindy.mayfieldKILLspamspamssf.sas.com> wrote:
> This is a serious question.  How do you "understand" how a circuit works and how do you create with your imagination a new one?
>
>
I'm still learning myself, though I'm further along.  I found my
understanding took a big leap after getting my ham radio license, it
covers a great deal of basic electronics.  I find I've become familiar
with certain structures, and look for them in schematics.  A voltage
divider using resistors is classic, and shows up all over the place.
Know ohm's law, E=IR.  Remember that transistors are *current*
devices, and need a resistor on either the collector or emitter side
to work.

I've also had good luck with application notes.
Maxim(http://www.maxim-ic.com ) has a HUGE collection of application
notes covering all manner of electronics design subjects.  Pick up a
copy of the ARRL Handbook, and build some stuff.  Doesn't matter if it
doesn't work, you'll be able to build it.  Build an audio oscillator
with a transistor, some resistors and capacitors.  Then scare all your
friends who needed a 555 to do the same thing:P




--
Paul Anderson
VE3HOP
KILLspamwackyvorlonKILLspamspamgmail.com
http://www.oldschoolhacker.com
"May the electromotive force be with you."

2007\01\28@101857 by John Chung

picon face
I am a programmer myself. I venture into PIC when I
decided to create my own door bell. I think the first
step in being better in electronics is determining
what you want to do. It did help me when I knew
assembly language for the x86. I always consider
myself low level programmer..... Anyway this is how I
approach electronics.

Read and re-read electronics , basic until you can
remember most or ALL of the basic stuff. Why? All the
advance stuff is based on the fundamentals. Take a
look at PWM. It has vector and wave theory it in. Most
of the stuff requires mere application of basic
fundamentals. It isn't too diff when you can *apply*
the basics into it.

The fun part of the advance stuff is the application
of the basics. I will read more electronics after
learning more maths. The branch of maths that you will
need is Calculus, trigonometry , matrix , number
theory and etc. If you truly want to calculate all the
magic values then you need maths.... Maths is the key
for more advance projects. Do not worry about maths
you just need proper guidance. I have some books for
maths if you really want to do your homework :)

Once again, basics rules. Maximum power and Maximum
voltage transfer is all based on fundamentals. Just
run through the Ohm law and you see why. Take your
time in understanding it. No point to continue when
the basics are not fully understood.

Once you have a better understanding on basic
electronics take up hobbist circuit and read through
it. Apply what you know and do it frequently. You will
get it.


Regards,
John Chung







--- Lindy Mayfield <RemoveMElindy.mayfieldTakeThisOuTspamssf.sas.com> wrote:

{Quote hidden}

> --

2007\01\28@113626 by Lindy Mayfield

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face

From: spamBeGonepiclist-bouncesspamBeGonespammit.edu [TakeThisOuTpiclist-bouncesEraseMEspamspam_OUTmit.edu] On Behalf Of Robert A LaBudde

2. Digital electronics is much easier for someone like you to get into, as
the states are logic-based, and programming is an extension of logic. I
don't think you would have much trouble picking up simple digital circuit
analysis.

>> This I had no problem with. (-:

3. Parts of electronics that involve electromagnetics (RF, radio,
magnetism, etc.) are difficult to understand without special courses and
considerable mathematics and experience.

>> Aha!  No wonder I didn't even get past the drawing board for my cell phone jammer. (-:

6. You should also obtain some test equipment (oscilloscope, multimeter,
frequency generator) and do some breadboarding experiments on simple
electronic circuits. A good way to start is to measurement the response to
different inputs, and try to validate the device specifications.

>> This I think is the key.  If I can SEE what is happening from one component to another, then I think I will make a huge leap in understanding.  I had just acquired a scope when I had to dismantle everything (because of moving and no place to work.)



2007\01\28@120039 by olin piclist

face picon face
Lindy Mayfield wrote:
> How do you "understand" how a circuit
> works and how do you create with your imagination a new one?

I'm going to answer the second question first.  I've seen several replies
from others and I think they are missing the question, which I think is "How
do you synthesize a circuit given a task you want it to perform?".

I design circuits for a living and I think I'm pretty good at it.  However,
it's not a easy process to explain because I'm not sure myself what all of
it is.  How would you explain to someone how to ride a bike?  However I was
intrigued by your question as a opportunity to think about the design
process itself in a structured way, something that hadn't occurred to me
before.  There are probably much better ways to break it down since I've
only had time for a few knee jerk thoughts, but off the top of my head I can
think of four components to designing a circuit.  I'll call them knowledge
of fundamentals, knowledge of components, synthesis, and details.

Knowledge of fundamentals is only partly what others have mentioned.  Yes of
course you need to know, and more importantly truly understand, Ohm's law
and others.  These are absolutely essential foundations without which any
further effort is pointless.  However they shouldn't be as daunting as
others have made them out to be.  Ohm's law is about as simple as it gets,
usually expressed as V=IR.  I usually think of it in the units form: Volts =
Amps x Ohms.  But just knowing the equation is only worth about 20 points
out of 100.  You must be able to truly feel or visualize what a resistor
does.  As you force more current thru it, the voltage accross it builds up.
As you make the resistor bigger, the voltage accross it builds up.  The
exact math isn't as important as the general feel and intuition that should
pop into your head whenever you think "resistor".  Now flip it around: Amps
= Volts / Ohms.  Can you feel that as you put more voltage accross a
resistor the current thru it will go up?  The third form, Ohms = Volts /
Amps is for the details part later.

Just like resistors, you must understand capacitors and inductors at this
same level.  The traditional equations are all over the books you've got,
but the way I *think* about a capacitor is Volts = Amps x Seconds / Farads.
Actually that should be "delta Volts", but we're getting into details.
Again, just being able to write and manipulate the equation is worth 20
points.  The other 80 points is for truly understanding and being able to
visualize what a capacitor does, screw the exact math.

With the addition of the equivalent description of a inductor, Amps = Volts
x Seconds / Henrys, you've got the fundamentals for most circuit work.

Knowledge of components means you need to know what's out there for use as
building blocks.  Just like when you write a computer program, you always
keep in the back of your mind the basic constructs: IF statement, GOTO
statement, FOR loop, computed GOTO, subroutine call, etc.  Your whole
program is built from these.  Your job as the programmer is to combine these
basic constructs into a bigger program that does what you want.  Obviously
there are resistors, capacitors, and inductors out there.  But knowledge of
components means knowing what real world realizations of these are actually
available and in what way they are limited.  The equations might look great
with a 5 Farad capacitor or 2 Henry inductor, but you have to know that such
parts are unrealistic for your little breadboard.  similarly you have to not
only understand the basics of how a NPN transistor works, for example, but
also know roughly the limitations of real parts and what real world
parameters are achievable.  For example, a real NPN transistor will have a
upper limit on collector current, it will turn on pretty quickly when you
cram current thru it's base, but won't shut off as fast.  You don't need to
remember the detailed numbers, just the general principles.  Data sheets are
there to answer the detailed questions.  This section is about knowing the
questions to ask.  Eventually you will remember details of things you use
often.

Synthesis is the part I think you were really asking about.  I mentioned the
other two first because you can't get here without them.  Synthesis is also
the hardest to describe and I have no idea how to teach it.  I've always
been pretty good at it, and don't really know how I learned it.  Again, how
did you learn to ride a bike?  How would you describe it to someone who has
never ridden a bike?  It does feel a lot like writing a program.  You know
what you want to achieve, so apply cleverness and creative thought into
stringing together the available components to meet that goal.  One
difference is that there is a lot more stuff you have to be aware of when
designing a circuit than when designing a program.  I think that is because
there are more differnet electrical components available, and they each have
their own set of real world quirks, unlike program components which always
do exactly what they're defined to do.  There are a few analogous quirks in
programming too though where you have to know what's really going on.  For
example, something might be nicely solvable by using a array.  If I wanted
all the prime numbers below 100, I could put them all in a array then cross
off ever second, every third, etc.  That works fine.  On paper that works
perfectly fine for prime numbers up to 1M or 10M too, but this is where a
real programmer realizes that this method eats up a lot of memory.  Maybe
that's fine, and maybe not, but this is the kind of quirk a good programmer
has to keep in the back of his mind when synthesizing a program.  A
theoretically correct program that requires 1Mbyte of array space is of no
value on a 18F252.  There are a few orders of magnitude more of these when
synthesizing a circuit, but it's kindof the same thought process.

Up until know you are only working out the basic form, often called
topology, of the circuit.  At some point you have to get out the fine tooth
comb and crank out the actual resistor values, check all the power
dissipations, etc.  In other words, you have to work out the details.  Just
like with programming where you've decided to generate prime numbers by
crossing off non-primes in a array, now it's time to sit down and write the
actual detailed code.  To me this is a very different thought process,
although of course the two are not always sequential and they are
intertwined.  You might think out the overall circuit in rough terms, then
design the details of a particular section, which might cause you to rethink
some of the higher levels as you find there isn't enough voltage here for
the range of something you want to do, too slow, too power hungry, etc, etc.
Sometimes this requires minor tweaks, sometimes more major (crap, I was
hoping to get away without boosting the voltage here, but working around it
turns out to be even worse).  Software works the same way.  Once you start
implementing the lower layers, you sometimes find that your original concept
of the overall structure needs some readjusting.

Your first question about how to understand a existing circuit it easier to
answer, although often I find it easier to design a circuit than to analyze
someone else's without having some idea what it does.  I think this is a lot
like computer code.  It's easier to write your own program to generate prime
numbers than to take someone else's undocumented code and figure out that it
generates prime numbers.  The solution is also the same in both cases.  You
go thru the design piece by piece to figure out what each of the parts do,
then build up to figure out what the overall thing does.  I think this is
where studying others' designs that have a good theory of operation writeup
is useful.  This is just like studying others' well documented code to see
how they solved a particular problem.  After a while you will learn some
tricks too that can be applied to your own designs.

If you want a exercise, take a look at the schematic to my USBProg PIC
programmer, http://www.embedinc.com/products/eusb2/eusb2.pdf.  I haven't
written up a theory of operation yet, so this is a good opportunity to try
to figure it out on your own.  Start at the beginning on the first page and
try to figure out what each component is doing, and what a few groups of
components are doing and why.  I'll be happy to explain a piece at a time
once you've taken a stab at it yourself.

Sorry my answers sounds more like "Zen and the Art of Circuit Design", but
there is no esacping the need for being able to visualize the voltages
(pressures) and currents (flow) and how all the components react to them.
In the end there is a strong component of intuition and "lore" from
experience that I find hard to describe.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2007\01\28@121745 by Alexandre Guimar„es

face picon face
Hi,

> 6. You should also obtain some test equipment (oscilloscope, multimeter,
> frequency generator) and do some breadboarding experiments on simple
> electronic circuits. A good way to start is to measurement the response to
> different inputs, and try to validate the device specifications.
>
>>> This I think is the key.  If I can SEE what is happening from one
>>> component to another, then I think I will make a huge leap in
>>> understanding.  I had just acquired a scope when I had to dismantle
>>> everything (because of moving and no place to work.)

   Just be very carefull because you will usually see "voltage" but in many
circuits the "current" is what really controls the transistors and with the
scope you will just see the "effects" of current at some load. Be carefull
with that..

   There are some books that are great to have around as close as possible.
:-) Two of my favorites is the old and faithfull "The Art of Electronics"
and another one that I could not live without is "The Circuit Designer's
Companion".

   A Spice simulator may also help a lot because you can "see" current
there :-) Be carefull because it is just a modeling tool and not the real
circuit.. I like Linear Devices "SwitcherCad" because it is quite easy to
use and the price is just right, free...

   Besides that the main thing is to read all you can get your hands at ;-)
I also have a background in programming and have been working as a hardware
designer for almost 10 years but as a hobby I started electronics long
before programming.. The piclist is the most incredible source of
information I have ever seen. Take a look at the archives and search for all
the posts from a guy named "Roman Black". He and Russel have a very nice and
quite unique way of describing the circuits they have published and it is
worthwhile specially because they make the analysis in a "intuitive" way
with very little math. There are many other people with invaluable posts on
the list. Unfortunatelly Roman and many others have decided to leave the
list but it is all in the archives...

   Asking questions around here usually works also. Just make sure you ask
them after you have done your "homework" and there will always be many
people willing to help, even if the questions are basic. Just make sure you
look around before asking :-)


Best regards,
Alexandre Guimaraes

2007\01\28@123434 by Alexandre Guimar„es

face picon face
Hi, Olin

> Sorry my answers sounds more like "Zen and the Art of Circuit Design", but
> there is no esacping the need for being able to visualize the voltages
> (pressures) and currents (flow) and how all the components react to them.
> In the end there is a strong component of intuition and "lore" from
> experience that I find hard to describe.

   My son is just 5 years old but I am saving your post just in case he
ever decides he want's to learn electronics someday :-)Your description of
the process was great ! Thanks...

   Have you ever thought about really writing something about the process
of circuit design ? Using your post as a basis and refining each step might
make a great tutorial for people starting at electronics design... Just a
crazy thought...

Best regards,
Alexandre Guimaraes

2007\01\28@123922 by Lindy Mayfield

flavicon
face
Thank you _very_ much, Olin, for taking the time to explain this in your own way.  I was actually hoping you would answer because I know you also teach electronics and I figured you'd have a good insight on ways to help someone along.

I'll really give your circuit a good look. But so far no one has answered my question on how/where to start.  Do I start at the + power supply and then make my way through all the components imagining in what "state" the current is in as it passes through each piece?

Lindy

{Original Message removed}

2007\01\28@124819 by Dario Greggio

face picon face
Alexandre Guimarães wrote:

>     My son is just 5 years old but I am saving your post just in case he
> ever decides he want's to learn electronics someday :-)Your description of
> the process was great ! Thanks...

I saved Olin's post as well, and put it at the end of a "Course for
Student, willing to learn about PC: software and hardware", which I
wrote some 10 years ago for a customers of mine, a Teacher, who wanted
to know how I had learnt all those things :-) , and which was the best
method to teach them. I was not meant to teach, I hope someone has used
those notes.

Thsnk you.

--
Ciao, Dario

2007\01\28@125331 by John Chung

picon face

--- Lindy Mayfield <RemoveMElindy.mayfieldspamTakeThisOuTssf.sas.com> wrote:

> Everyone has given me good advice, which I will
> follow.  But what I don't understand is how you -- I
> don't know the words I'm looking for -- how you read
> a circuit.  If it were a program, I'd could start at
> the beginning and follow the flow keeping track of
> variables, like a debugger does.
>
> I think I'm trying to do that with circuits and sort
> of my question is, am I doing this right, or is
> there a proper way that I haven't figured out yet?
> Do you start at + and work your way to - ?
>
> I read every single "how it works" I find, and I
> understand a bit, but I don't quit get it in a way
> where I could look at a circuit and tell what it
> does.
>


 You could make things simpler by drawing a  flow
diagram of the circuit. Take a big snapshot of the
circuit and then zoom down to the areas of interest.
Treat areas that you are not sure as black box. Just
like programming. Then later on use your meter or
scope to look at details that you want to know about.

For example. This section is for power. How power is
handled and maintained are details. Zoom in when you
are interested in it. Open the book when you need to
see the relationship between theory and practice. That
is about it. Break is down over and over again. Just
like programming do not assume what was previously
done just know what you are expecting here at this
point in the circuit. Impedence or etc of the previous
circuit need not to be calculated until you need them.

Well that is how I do things.

John


PS: start with the basic theory*on the circuit* first
before moving to more exotic stuff like thevnin
theorem. Rarely needed to be applied unless you are
doing circuit analysis.




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2007\01\28@130127 by David VanHorn

picon face
>
>
> Sorry my answers sounds more like "Zen and the Art of Circuit Design", but
> there is no esacping the need for being able to visualize the voltages
> (pressures) and currents (flow) and how all the components react to them.
> In the end there is a strong component of intuition and "lore" from
> experience that I find hard to describe.


Good description.

I've always called it "seeing the shape of the circuit", and it's somewhat
similar to pseudocode.

>From the basic requirements, I know the big parts, like I need an op-amp
here, a mosfet there, and so on.
Resistors and other passive components get planted where they need to be.
Later, I refine this by actually calculating the required values, though in
a lot of cases no real "calculation" is needed, since the values aren't all
that critical, or the ratio of the values is far more important than the
actual values.

2007\01\28@135845 by Wouter van Ooijen

face picon face
> I'll really give your circuit a good look. But so far no one
> has answered my question on how/where to start.  Do I start
> at the + power supply and then make my way through all the
> components imagining in what "state" the current is in as it
> passes through each piece?

I do that only for a basic circuit that is new to me. A 'real' circuit
often consists of a number of basic circuits, which I recognise and
'read' the same way I read text: not letter by letter, but word by word,
and somtimes even a whole phrase at a time. You've got to learn the
'pattern language'.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2007\01\28@140959 by Herbert Graf

flavicon
face
On Sun, 2007-01-28 at 16:05 +0100, Lindy Mayfield wrote:
> Everyone has given me good advice, which I will follow.  But what I don't understand is how you -- I don't know the words I'm looking for -- how you read a circuit.  If it were a program, I'd could start at the beginning and follow the flow keeping track of variables, like a debugger does.
>
> I think I'm trying to do that with circuits and sort of my question is, am I doing this right, or is there a proper way that I haven't figured out yet?  Do you start at + and work your way to - ?

The way I read circuits is like how you read a sentence. When you read a
sentence you don't see a series of letters, instead you see a series of
words made up of letters. Each word has it's own meaning, and when you
couple two words they increase (or refine) their meaning.

It's similar with circuits. I don't see a bunch of transistors, a few
resistors, a power and a ground. I see a transistor in common emitter
config, AC coupled to a class B driver stage, connected to a speaker.

This sort of thing comes with experience. Alot I learned on my own, some
I learned in University. There are areas were you must understand a
least some of the math to get a grasp of how a circuit is supposed to
work (i.e. AC circuit analysis, small signal analysis).

The best way IMHO to start is to start building the basics. Start with
resistors and voltage sources. Learn what a resistor divider is, the
series and parallel rules, thevenin equivalents.

When you are comfortable with that, start with op amps, they are
mathematically very simple (from a 1st order approximation point of
view) yet can do amazing functions (amplify, invert, integrate,
differential, etc).

Once you grasp that try going "deeper". Learn the standard BJT
transistor configs and build them, experiment with them, tweak them.

At this point you are ready for small signal type stuff. This is where
math becomes more important, but you're still in the realm of being able
to build useful circuits that demonstrate the math.

Different people learn different ways. To me, learning the theory was
OK, but actually building the circuits is where I truly started to
understand how things work. Also, building the circuits gives you an
instinctual insight into how things work, so you aren't just memorizing
formulas, you're actually understanding WHY the formulas are the way
they are.

TTYL

2007\01\28@142235 by olin piclist

face picon face
Lindy Mayfield wrote:
> But so far no one has
> answered my question on how/where to start.  Do I start at the +
> power supply and then make my way through all the components
> imagining in what "state" the current is in as it passes through

If you trust the circuit designer you can just assume the power supplies are
what they are labeled to be.  The real analysis is about the information or
signal flow.

Just like most programmers suck at comments to the point of crimnal
irresponsibility (if I was making the laws), unfortunately too many EEs are
just as bad at making schematics easy to understand.  I try hard to make my
schematics at least somewhat intuitive.  Power rails generally are
horizontal on a page, and higher for higher voltage.  I try to keep signals
flowing left to right, except feedback paths which loop back from right to
left.  Of course it's impossible to stick to these all the time, especially
with general purpose ICs like PICs.  I do what I can in those cases, like
put power leads at the top, ground at the bottom, and arrows on other lines
to give a clue which direction the information (not the current!) is
flowing.

So to answer your question with my schematics, start at the left side of a
page and work towards the right, in general.  For other schematics, try to
follow the signal or information flow.  For some parts, like opamps this is
easy since they have obvious inputs and outputs.  Other parts are not so
easy and you have to sit down and figure it out.  There is no magic method.

After a while you will recognize some constructs and won't have to analyze
their details every time.  Examples are emitter follower, voltage divider,
inverting and non-inverting opamp amplifier, simple single pole R/C low pass
filter, etc.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2007\01\28@142308 by Cedric Chang

flavicon
face

Electronics is like many disciplines.  You can attack it "top-down" or
"bottom up" or sideways.

I started out learning from the "bottom". Ohm's law, how a capacitor  
works, that sort of thing.

Then I started reading electronic trade magazines and read about  
every "building block" that
suppliers were offering.  ADCs, multipliers, USB to Serial, etc.  As  
time as gone on , the "building
blocks" get more awesome and powerful.

Now I look at a design issue as an adventure in finding the right  
building blocks.

CC

{Original Message removed}

2007\01\28@143514 by Dennis Crawley

picon face
Lindy Mayfield wrote:
> This is a serious question.  How do you "understand" how a circuit
> works and how do you create with your imagination a new one?

Lindy, this book and the whole collection from this autor makes me
understand a lot.
Robert L. Boylestad "Introductory Circuit Analysis", etc.
In Communication area, Wayne Tomasi,... I don't remmember the title :)



Regards,
Dennis.





2007\01\28@144059 by David VanHorn

picon face
>
>
> Just like most programmers suck at comments to the point of crimnal
> irresponsibility (if I was making the laws), unfortunately too many EEs
> are
> just as bad at making schematics easy to understand.


I could not possibly agree more.

There is a school of thought that puts pins on chips in a schematic in the
same orientation as on the physical chip.  Readability be damned, they are
determined to make it easy to count pins. (like it was ever hard?)  This
procrustean solution to a non-problem results in gordian knot schematics
that almost completely obscure the shape of the circuit.

I would compare this to putting the labels in a program in alphabetical
order and "fixing" the resulting mess with gotos.

:-P

I know it takes all kinds, but I think we could do with less of that kind.

2007\01\28@160444 by olin piclist

face picon face
David VanHorn wrote:
> There is a school of thought that puts pins on chips in a schematic
> in the same orientation as on the physical chip.  Readability be
> damned, they are determined to make it easy to count pins.

Yeah, and some absolutely insist on that.  I did a article for Circuit
Cellar on digital power factor correction that came out about a year ago.  I
submitted my schematics in nice readable form with the pins on the PIC layed
out according to function.  They insisted on changing that so that they were
layed out according to pin number.  I objected, but they insisted on doing
it their way.  I put the readable version of the schematic on my web site so
I wouldn't look quite so stupid.

I know there are people who believe in it both ways, but I was rather
surprised someone believed in the obsure way so strongly as to not let the
author of a article do it his way.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2007\01\28@161956 by David VanHorn

picon face
>
>
> Yeah, and some absolutely insist on that.  I did a article for Circuit
> Cellar on digital power factor correction that came out about a year
> ago.  I
> submitted my schematics in nice readable form with the pins on the PIC
> layed
> out according to function.  They insisted on changing that so that they
> were
> layed out according to pin number.  I objected, but they insisted on doing
> it their way.  I put the readable version of the schematic on my web site
> so
> I wouldn't look quite so stupid.


Boy, do I know how you feel..
The job of a schematic is to convey information. NOT to help you find pins.

2007\01\28@171706 by Herbert Graf

flavicon
face
On Sun, 2007-01-28 at 16:19 -0500, David VanHorn wrote:
> >
> >
> > Yeah, and some absolutely insist on that.  I did a article for Circuit
> > Cellar on digital power factor correction that came out about a year
> > ago.  I
> > submitted my schematics in nice readable form with the pins on the PIC
> > layed
> > out according to function.  They insisted on changing that so that they
> > were
> > layed out according to pin number.  I objected, but they insisted on doing
> > it their way.  I put the readable version of the schematic on my web site
> > so
> > I wouldn't look quite so stupid.
>
>
> Boy, do I know how you feel..
> The job of a schematic is to convey information. NOT to help you find pins.

Hmm, see, that's where there might be a disconnect between an
experienced person, and a lesser experienced person.

First off let me say that grouping pins on a part in a schematic based
on pin numbers is NOT the way I'd go. Grouping pins based on function is
FAR better (i.e. I prefer, when possible, powers on the top, grounds on
the bottom, inputs on the left, outputs on the right, bus bits grouped
together with associated pins (i.e. clocks). I'm not stuck to this
however, for example for a MAX232 I would put TTL levels on one side and
RS232 levels on the other.).

That said, let us consider the readers of a magazine such as Circuit
Cellar. While many of their readers are experienced and would prefer a
schematic with pins being grouped by function, let us consider the
lesser experienced readers.

These are readers new to electronics. They don't fully understand a
schematic. To them, a schematic has NOTHING to do with how the circuit
works, it's simply a recipe for building the circuit. To them, pins
assigned based on pin number is FAR easier to grasp since they are
holding the physical part in their hands. The function of each pin is
less important since they don't understand the circuit much anyways (if
you don't know what MCLR is, why does it matter where it goes on a part,
just connect it to this resistor thing that's connected to this power
supply thing).

Yes, some here will say "well, these beginners should get used to how
things are done properly", and I'd agree with them, to a point. What's
better in a magazine with such a distribution of reader skill sets: a
schematic that's a little harder to read for an experienced person, or a
schematic that's harder to reader for the beginner?

I'd say making the schematic easier for the beginner is the right
choice. The experienced person will be a little annoyed, but it won't
dissuade them very much. The beginner on the other hand will likely quit
VERY quickly if the schematic doesn't match what they are holding in
their hands.

As an author like Olin I would have also been annoyed, but I understand
their choice, and while I may not like it, I do agree it is the better
choice.

Just my opinion. TTYL

2007\01\28@172202 by Jinx

face picon face
> If it were a program, I'd could start at the beginning and follow the
> flow keeping track of variables, like a debugger does

A program or circuit might not necessarily be that simple. There could
be "feedback" loops - the state of one part affects the state of another.
You could equate analogue voltages in one part of a circuit with variables
(eg a count) in an ISR. The voltage on the sensor in an alarm system for
example. Programs and circuits cover the range from menially simple
to mind-blowingly complex, but they are all based on principles

> I think I'm trying to do that with circuits and sort of my question is,
> am I doing this right, or is there a proper way that I haven't figured
> out yet?  Do you start at + and work your way to - ?

An important point here IMO is that analysing and designing are
completely different

For example I see other people's programs and think, oooh, I wouldn't
have done it like that, doesn't suit my style. Similarly with circuits,
although cost is often a factor that could affect how it is built (there is
labour, and ingenuity, associated with programming but copies are
essentially free). Smart programming can save materials too of course

Maybe a zener will do instead of a regulator, after the conditionals are
considered - is there enough power available to waste on a zener, is
the zener voltage good enough, should I buy that clearance lot of 10c
regulators ........

I've re-engineered prototype circuits that were built with OTS parts
and money was no object (primarily because the person who built
them didn't know enough to select better, he just wanted the job done)

When faced with a prototype to build, I don't often need to pull another
circuit apart to get started. I know how I would do it and take it from
there. Reading the datasheets / application notes for unfamiliar ICs is
always a good step

> Certain components and groups of components we know do various
> things. Like little modules (or subroutines or function libraries).  And
> that when designing something you know which of these modules to
> put where to do what

The program / circuit analogy mostly works, but is a little simplistic. It
could equally apply to fashion. A button is digital (worked by fingers
and has two states), a zip could be considered analogue. Trousers are
digital (up or down), dress length is analogue and could be considered
logically

IF dress length < X THEN undies = 1 UNLESS Britney AND tramp

> I just think I'm not looking at the big picture correctly.

What will come with experience is intuition. Then you can visualise a
concept and instinctively know whether it's feasible and how it could
be put together. You need to study working circuits, measure them,
make substitutions and so on. Theory is an important part of the deal
but hands-on familiarity with components that don't appear to behave
ideally is just as important. After all, customers want a practical
circuit that DOES the job, not a theoretical one that SHOULD have

2007\01\28@173615 by William Chops Westfield

face picon face

On Jan 28, 2007, at 5:00 AM, Vasile Surducan wrote:

> You have an advantage being programmer (the advantage is your logic,
> assuming all programmers have good logic) but usually software
> programmers have serious leackage in basic of electronics and they
> start without having the smallest ideea about how really a transistor
> works.
>
heh.  You may be trying to understand too much.  The details of how
a transistor operates are no more important to understanding the
average electronics circuit than the the details of horizontal vs
vertical microcode or red/black trees vs radius trees in the average
piece of software.

When I got my EE degree, we spent a long time learning calculus, and
physics, and then applying that to components and semiconductors, only
to spend our final year working with simplifications like phasors,
ideal op-amps, and digital gates.  I don't think "real" EEs deal
very much with individual components; it's more like "this segment
is a low-pass filter, and this is a comment emitter amplifier, and
this over here is an analog integrator, but this transistor is just
a switch..."  There are more complicated circuits, of course, just
as there are programs that are on the edge of research in computer
science, but I don't think they come up as often as you might think.

BillW

2007\01\28@174011 by David VanHorn

picon face
>
>
> First off let me say that grouping pins on a part in a schematic based
> on pin numbers is NOT the way I'd go. Grouping pins based on function is
> FAR better (i.e. I prefer, when possible, powers on the top, grounds on
> the bottom, inputs on the left, outputs on the right, bus bits grouped
> together with associated pins (i.e. clocks). I'm not stuck to this
> however, for example for a MAX232 I would put TTL levels on one side and
> RS232 levels on the other.).


Mostly, I agree.  I tend to put power and ground where I can show the bypass
caps connected there, so that I'm conveying that information to the layout
guy. In general, I'm more picky than most on bypassing, but I get better
results. :)  Would you believe in connecting three points 0.2" apart with
0.1" trace, I can get a 2dB improvement in switcher output noise by
connecting them in the right order, as opposed to a triangular "blob" that
connects all three?


> These are readers new to electronics. They don't fully understand a
> schematic. To them, a schematic has NOTHING to do with how the circuit
> works, it's simply a recipe for building the circuit.


Well, pandering to that is in some ways a mistake.
I would add in a small pic showing the pinout, but even that is wasted
space.
The magazine has the additional constraint of a finite amount of space to
show things in.


> Yes, some here will say "well, these beginners should get used to how
> things are done properly", and I'd agree with them, to a point. What's
> better in a magazine with such a distribution of reader skill sets: a
> schematic that's a little harder to read for an experienced person, or a
> schematic that's harder to reader for the beginner?


Reasonable point.

I'd say making the schematic easier for the beginner is the right
> choice. The experienced person will be a little annoyed, but it won't
> dissuade them very much. The beginner on the other hand will likely quit
> VERY quickly if the schematic doesn't match what they are holding in
> their hands.


This isn't helping the inexperienced become experienced, but that isn't
really the goal of the magazine.. But it does perpetuate the myth that this
is the "right" way to do things, and it contributes to "dumbing down".

2007\01\28@180951 by William Chops Westfield

face picon face

On Jan 28, 2007, at 10:58 AM, Wouter van Ooijen wrote:

>> Do I start at the + power supply and then make my way
>>  through all the components imagining in what "state"
>>  the current is in as it passes through each piece?
>
> I do that only for a basic circuit that is new to me. A 'real'
> circuit often consists of a number of basic circuits...

Right.  What Linday proposed would be equivalent to analyzing a
C++ program by looking at the machine code.  First step; learn
to recognize the "subroutines" and basic hardware constructs.

BillW

2007\01\28@182752 by peter green

flavicon
face
> When you are comfortable with that, start with op amps, they are
> mathematically very simple (from a 1st order approximation point of
> view) yet can do amazing functions (amplify, invert, integrate,
> differential, etc).
>
> Once you grasp that try going "deeper". Learn the standard BJT
> transistor configs and build them, experiment with them, tweak them.
just don't get too "clever" if you wan't things to work, for example back when i was doing my A-Level electronics i built a cuircuit that didn't work (supposed to be an audio amplifier, ended up as a rf noise generator) and my tutor couldn't understand why it didn't either. Turns out that adding a high gain but highly nonliniar inverting transistor amplifier stage to the output of an op-amp and taking the feedback to the positive terminal isn't such a good idea even though according to the models of op-amps they teach you at that level it should work.



2007\01\28@183848 by William Chops Westfield

face picon face

>> First off let me say that grouping pins on a part in a schematic based
>> on pin numbers is NOT the way I'd go.

I want a schematic drawing utility where I can move the pins around
after it's drawn.  Logical pin grouping is fine, but I'd also like
to have some clue when I'm drawing a schematic just HOW BAD the
resulting PCB layout is going to be (especially when dealing with
pins basically interchangeable, like uC output pins...)

Currently I turn on pinswappability in eagle and munge the PCB, but
the schematic comes out ... extremely icky.  The alternative that I
see professionally is a schematic that shows little more than a pin
going to a label, with the other end of that label someplace on
another page.  The schematic is neat, and the pins are grouped by
function, but the overall structure is not at all clear...

BillW

2007\01\28@185450 by Herbert Graf

flavicon
face
On Sun, 2007-01-28 at 23:27 +0000, peter green wrote:
> > When you are comfortable with that, start with op amps, they are
> > mathematically very simple (from a 1st order approximation point of
> > view) yet can do amazing functions (amplify, invert, integrate,
> > differential, etc).
> >
> > Once you grasp that try going "deeper". Learn the standard BJT
> > transistor configs and build them, experiment with them, tweak them.
> just don't get too "clever" if you wan't things to work, for example back when i was doing my A-Level electronics i built a cuircuit that didn't work (supposed to be an audio amplifier, ended up as a rf noise generator) and my tutor couldn't understand why it didn't either. Turns out that adding a high gain but highly nonliniar inverting transistor amplifier stage to the output of an op-amp and taking the feedback to the positive terminal isn't such a good idea even though according to the models of op-amps they teach you at that level it should work.

Actually I'll say: get too clever.

The best way to learn IMHO is to make mistakes. Because you made a
mistake like this it's ALWAYS going to be in the back of your mind and
you're a better designer because of it.

TTYL

2007\01\28@185759 by David VanHorn

picon face
> Turns out that adding a high gain but highly nonliniar inverting
> transistor amplifier stage to the output of an op-amp and taking the
> feedback to the positive terminal isn't such a good idea even though
> according to the models of op-amps they teach you at that level it should
> work.


Simulation can decieve you, don't trust it!..

I'm with Bob Pease on that one..  The best simulator is solder.

2007\01\28@191306 by peter green

flavicon
face

> > Turns out that adding a high gain but highly nonliniar inverting
> > transistor amplifier stage to the output of an op-amp and taking the
> > feedback to the positive terminal isn't such a good idea even though
> > according to the models of op-amps they teach you at that level
> it should
> > work.
>
>
> Simulation can decieve you, don't trust it!..
indeed it works (once you unbalance it slightly so the simulator doesn't hang) in crocodile clips (which made it all the more puzzling for me at the time.


2007\01\28@191731 by Rich

picon face
The best way to learn electronics is by getting every rudimentary book you
can find from the library, set up a rudimentary lab and complete all of the
experiments.  The move on to more sophisticated circuit theory.  There are a
lot of circuit analysis book.

If you follow the syllabus in the first link, you can come up to speed in a
hurry.  What you get out is what you put in.  I always outline a new topic
in a notebook.  Writing things in long hand helps me to remember and I
suspect it works in general.

http://www.bu.edu/eng/leap/Course_Syllabi/EK307syllabus.htm

http://www.engnetbase.com/ejournals/books/book_summary/summary.asp?id=4593

http://www.electro-tech-online.com/

www.bu.edu/eng/leap/Course_Syllabi/EK307%20Online%20Syllabus_Sum04.ht
m

http://www3.interscience.wiley.com/cgi-bin/jhome/1976?CRETRY=1&SRETRY=0

http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=8148






----- Original Message -----
From: "Cedric Chang" <CedricEraseMEspam.....nope9.com>
To: "Microcontroller discussion list - Public." <EraseMEpiclistspammit.edu>
Sent: Sunday, January 28, 2007 2:23 PM
Subject: Re: [EE:] How do you create and understand circuits? (i.e. why
amisostoopid)


{Quote hidden}

> {Original Message removed}

2007\01\29@004856 by Lindy Mayfield

flavicon
face
I see.  Like when I was talking about "modules" which I guess would be phrases and not necessarily words.  Good points.  AND something I have to learn more than just what a resistor does or a capacitor does.  I have to know what they do together.

{Original Message removed}

2007\01\29@005935 by Lindy Mayfield

flavicon
face
I have a 50 pound gift certificate for xmas present that I think I'll use on the Boylestad book.  
Which book did you mean by Tomasi?
http://www.amazon.co.uk/exec/obidos/search-handle-form/203-5364040-3666301

Lindy

{Original Message removed}

2007\01\29@010211 by Lindy Mayfield

flavicon
face
That thought never crossed my mind.  

Which conversely means I have to learn how to properly arrange components, too.  Not just for RF reasons, etc.

You guys are great on this list.  I think, or I hope, it is because I've really demonstrated that I've really, really tried before asking this question. (-:


{Original Message removed}

2007\01\29@021639 by William Chops Westfield

face picon face
>> Simulation can decieve you, don't trust it!..
>>
geez.  If you're just starting learning about hardware, I hope
you're NOT dealing with circuits where the simulation is too
far different from reality...

BillW

2007\01\29@062820 by Dennis Crawley

picon face
"Lindy Mayfield" wrote:
> I have a 50 pound gift certificate for xmas present that I think I'll use
on the Boylestad book.
> Which book did you mean by Tomasi?
> www.amazon.co.uk/exec/obidos/search-handle-form/203-5364040-3666301
> Lindy

Lindy,
The title is "Electronic Communications Systems" (Fundamentals Through
Advanced)
You will learn communications from the beginning to GSM and satellites.

As well as Boylestad does, each chapter ends with exercises.
I think is a good idea to start with Boylestad, "Introductory Circuit
Analysis".
Then "Electronic Devices and Circuit Theory"
Try to get them all used.... :)

The books sometimes assume you know how to operate with complex numbers and
some algebra rules. Well, electronics is math! Don't let this get you down.
Algebra, functions, differentiation, integration, differential equations
(first a second order, stop there), Laplace and Fourier transforms. This is
enough to understand almost everything. It is obvious that "the more the
better", but you don't have to deal with large and annoying integrals all
the time, so skip the complex ones, you'll never use them!

I highly recommend my math companion book "Applied mathematics for Radio and
Communication Engineers" Carl Smith, (The Pentagon, Washington, DC 1945!):))
Good luck! Keep it simple.
Dennis.






2007\01\29@072619 by olin piclist

face picon face
Lindy Mayfield wrote:
> You said if I took a crack at your circuit and really gave it a go,
> you'd advise me.  Should I do this on list or off list?

Circuit analysis has generally been considered appropriate here before.
There may be others interested as well.  If James disagrees, I'm sure he'll
let us know.

I was figuring you pick a small part of the circuit at a time, on the order
of half a schematic page or so, explain what you think it does, how it
works, why the particular choices were made, what considerations were
envolved, etc.  Others may want to take a stab at it too.  I suspect that
once you and anyone else that wants to practise analysing a circuit has
finished kicking it around I'll have little left to add, but I can at least
confirm what my reasoning was.  I expect some experts will chime in
explaining how I was being silly and how they would have done it.  That's
fine too.

To make sure we're all on the same page, the particular circuit we are
discussing is http://www.embedinc.com/products/eusb2/eusb2.pdf.

A good start might be to explain the sub-circuit of R2, D3, C2, and Q1 near
the center of page 1.  What does it do?  Why is it needed?  Explain its
detailed operation.  What does each part do?


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2007\01\29@073757 by Vasile Surducan

face picon face
On 1/29/07, Olin Lathrop <RemoveMEolin_piclistEraseMEspamEraseMEembedinc.com> wrote:
{Quote hidden}

And what's hapening if Q3 drain-source or Q3 internal diode is short
circuiting....
:)
Are you always believe into the OTG USB power supply as current limiting ?
(like it should...)

Vasile

Vasile

2007\01\29@095604 by Alan B. Pearce

face picon face
>Right.  What Linday proposed would be equivalent to analyzing a
>C++ program by looking at the machine code.  First step; learn
>to recognize the "subroutines" and basic hardware constructs.

Pretty good analogy, to my way of thinking.

>I do that only for a basic circuit that is new to me. A 'real' circuit
>often consists of a number of basic circuits, which I recognise and
>'read' the same way I read text: not letter by letter, but word by word,
>and somtimes even a whole phrase at a time. You've got to learn the
>'pattern language'.

That really is it - and many of the patterns will be in "The art of
Electronics" in the form of simple circuit diagrams.

Items you look for: -

analogue amplifier (block) -
could be discrete components or could be an IC. There will be some feedback
around it somewhere to set the gain (although some of the feedback methods
may not be obvious to an untrained eye). The way the feedback is applied
versus the point at which the signal is fed in may also determine if the
signal is inverted in the amplifier, or not. See the block diagram in
Horowitz and Hill for examples of inverting and non-inverting amplifiers.

Multivibrator block -
Someone has already posted links to pictures of the "right" and "wrong" ways
of laying these out.
Could be made out of a pair of transistors, or a pair of logic gates. Also
has various forms, some of which do not have capacitors, some have one
capacitor, and some have two. With two capacitors the circuit will oscillate
with a square wave output. With one capacitor the circuit will act as a
one-shot, which times out at some period after being triggered. With no
capacitors it is a bistable item, which flips state when an input is
triggered. The computer flip-flop is an "advanced" form of this last
version, and can have a variety of extra inputs for setting or resetting to
a known state, or allowing the state change to occur only when a certain set
of conditions are on the input pins. names such as "R-S", "J-K", "D", "edge
triggered", "synchronous" and "clocked" abound in this field.

Power Supply -
usually pretty obvious on the circuit, and will give an indication of the
voltage, and maybe current, available. E.G. a supply listed as "LED Volts"
or "Display volts" is likely to be a higher current capacity, or less well
filtered or regulated, than
"microprocessor supply". For analogue circuits there may well be both
positive
and negative supplies, as many analogue signals will go both polarities with
respect to ground. Finding positive and negative voltages around a digital
circuit may well mean that there is an Analogue to Digital converter present
which can convert both positive and negative voltages.

Bus Lines -
Normally would only appear on a digital area of a circuit. Think of them as
a multi-lane highway, with sideroads coming off, or a bundle of wires in a
cable tie with a wire coming out of the bunch. On a circuit that is usually
how they appear, as a thick line with thin lines coming off. Used to prevent
too many parallel lines from one point to another from confusing the overall
information flow of a schematic, and signifies they are all "related", with
relevant signals being pulled out from the bunch as needed. The "highway" or
"wire bundle" analogy is limited in that the analogy doesn't include the
possibility of a particular signal having multiple connections made to it,
e.g. the address and data busses from a processor going to RAM, ROM and I/O
chips. The address and data lines may well go to all chips, but the chip
select lines may join only two points, but be included in the "bundle".

Wiring -
Keep a check on signs that shielded or twisted pair wiring is used. This may
indicate sensitive or low level signals present, or lines that may radiate
unwanted signals which will cause EMI interference.

2007\01\29@101019 by alan smith

picon face
Oh..suppose I shouldnt chime in...but whats one more opinion?
 
 First, Olin had a very good post, excellent post in fact.  As expected actually.  Olin is a smart guy, and he knows it, and has been around doing this stuff for some time.
 
 But in general, to understand what a circuit is doing, break it up into blocks.
 
 ....input...processing....output.  
 
 Now of course that doesnt apply to every circuit but often will.  In addition can be, but not always...power supply as well.  So once you have it divided up (multi sheet schematics will often have those blocks on individual pages as well) you can look at them a little more closer.  Analog inputs sometimes need conditioning, so might be some small signal amplification going on...could be by transistors or maybe op-amps.  Often on a schematic, I'll note what the gain is suppose to be, or what is to be expected.  Processing...maybe there is a micro, or dsp, or just some gates.  Output...relays, amplifiers again...who knows what.  So that helps in understanding a circuit.
 
 Creating a circuit, can work the same way.  Start with a block diagram, essentially a flowchart in some ways.  You have some inputs...be it analog or digital....you have a desired result to occur...how is that to be intefaced with the outside world.
 
 Might be...digital...analog....RS232...wireless....block diagram just has it labled as such....
 
 The middle processing part....thats where it becomes YOUR cleverness in design...how are you going to get the desired results from the inputs.
 
  Processor....CPLD....FPGA....DSP...jelly bean logic...your design, so you decide how to resolve it.  If you building a million...might be cheaper to do gates or transistors or fets....if its single device for you...PIC might be easier...but not cheaper, so always have to keep in mind the trade offs of cost vs ease of design.  And nothing says you cant make it cheaper once you have the proof of concept done.
 
 There are engineers that spend a career in electronics, and still have a difficult time with the concept part, but once thats laid out for them...they can pick and choose the pieces for it.  Others are great concept guys....but can't always choose the best parts to use.  Other engineers run fast when they see anything analogish in a design...they spent the career in the digital world.  Some, if they are lucky....can have a foothold in all areas......a very few (and some are on this list) have a great grasp of it all.  They can dream up a solution to a given problem....choose just the right parts to get it done.....create schematics.....do a board layout and write firmware if needed.  They also know how to design it so it can be built.  Now of course alot of that comes from experiance, and being mentored and simply asking the right questions.  And having the KNACK for it.
 
 Myself.  I'm no expert in any of the areas. But I know enough to get in trouble in most of the areas.  And never afraid to ask questions when something isnt working quite as expected or even if I have not much of a clue on how to resolve something.
 
 -AS



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