Re: Software for a beginner to design and learn about circuits with?

From: mike (spamme0_at_netscape.net)
Date: 12/01/04 

Date: Wed, 01 Dec 2004 02:23:45 -0800

Kevin Aylward wrote:
> mike wrote:
>
>>msv-groups wrote:
>>
>>>Hi,
>>>
>>>I'm interested in learning about circuitry as a hobby and to
>>>eventually create a few small projects that I had in mind, such as
>>>guitar pedals and a few audio devices, but obviously I have to start
>>>small. I'm somewhat competent with programming/mathematics, have some
>>>text
>>>books, and I do know a -little- analogue+digital circuit theory, but
>>>I've never had a real hands-on attempt by myself before so I'll be
>>>pretty much attacking this as though I know nothing.
>>>
>>>Can anyone recommend some software (free or cheap) that would be good
>>>for a beginner to use to learn about circuit behaviour and design
>>>some circuits with? Are there programs out there that actually
>>>allow you to drop in popular microcontrollers and model their
>>>behaviour as well? Thanks,
>>>Matt.
>>
>>Wait while I get up on this her soapbox.
>>
>>Circuit design is the process of turning an idea into an
>>implementation concept into a bunch of hardware and/or software to
>>realize the idea.
>>For this you don't need software. You need a BOOK!!!
>>Go to the library and check out a book on analog circuit design.
>>Learn about Ohm's law, norton's theorems etc. Learn about rc/lc/rlc
>>circuits. How to bias a transistor, FET etc. Learn how to do Laplace
>>transforms. You're rarely gonna do a laplace transform, but the
>>knowledge of how, gives you great insight into what's gonna happen
>>when you change a circuit paramaeter or topology. It allows you to
>>pick component values right out of the air that are very close to
>>what you'll finally end up with after you fine tune it. It tells you
>>instantly when you're way off base and need a different approach.
>>If you need a calculator, you're going too deep. Your objective is to
>>be able to scratch out a circuit topology, estimate bandwidths, gain,
>>impedance, signal fidelity etc. Learn about component parasitics.
>>Unless you're doing audio work, a resistor is not just a resistor. And
>>it goes downhill from there. Learn how real components have
>>parasitics and vary relative to their specifications and how to
>>mitigate the impact of those variations on your objective.
>
>
> All good general advice.
>
>
>>Learn about Fourier transformations betwee time and frequency domains.
>>Again, you're rarely gonna do one by hand, but knowing how gives you
>>great insight into topologies and components required to realize your
>>design.
>
>
> All good general advice.
>
>
>>Now, go back to the library and checkout a book on digital circuit
>>design.
>
>
> Nope.....
>
> Digital is for those just to stupid to do analogue:-)

Hmmmm. Digital is a GROSS simplification of analog so you can
deal with the concepts more easily. Isn't that how simulators work?
Ain't nothing wrong with working in the digital domain as long as you
go back and verify your work in the analog domain. But if you're using
a simulator and don't understand digital or analog, you're in deep...

>
>
>
>>Learn that ALL curcuits are analog and that most digital
>>problems have to do with the ignored analog characteristics of the
>>digital simplification. Learn about Karnaugh maps, glitches, races
>>etc.
>>Now, you know how to design circuits. It's time to start looking at
>>software to simulate the circuit you've already designed to fine tune
>>it's parameters and take into consideration the simplifications you
>>used to design it in your head or with a pencil.
>
>
> I can't agree at all.

This is fundamentally wrong in my opinion, and
> that of probably every educator known to man. If this were true, there
> would be no lab work until 3rd year of uni. The best way to learn is to
> do little bits of theory at a time complemented by practise to reinforce
> that theory. A simulator is indeed *real* practise, excluding the few %
> issues like parasitics. Too many here are going, well because a
> simulator doesn't copy everything exactly from the real world, then it
> is sadly lacking for real world learning. This is very narrow minded.
> *Most* of what a simulator can do is very good model of the real world.
>
> Spending several years doing the "basics" before even getting started on
> trying out the theory is quite daft.

I do so enjoy reading your posts. You seem to get a lot more out of
my posting than I wrote. I never said anything about how long it should
take. Never said you shouldn't do bench work along the way.
Point I was trying to make is to leave the simulator out of the picture
until you have a basic understanding.

One would simply forget what one
> first learned. To all intents and purposes, there is no practical
> difference between examining ohms law and I=cdv/dt on the bench or in a
> simulator. Your brain, eyes and ears are processing essentially, the
> same information. There is only this vague psychological issue that some
> have about it "not being the same". Essentially, it is.
>
>
>>Circuit simulation replaces the tedious VERIFICATION calculations that
>>we used to do by hand.
>
>
> Unfortunately, in a real design of 100s to 1000s of components, hand
> calculations are impossible. Even a one transistor circuit has no exact
> analytical solution.

Who said anything about exact analytical solutions? I GUARANTEE you
that I can do calculations on a design with 100s of components.
I didn't say what calculations.

>
>
>>It does NOT replace the thought processes needed to design circuits.
>
>
> It can do. This is the reality of how it works in the real world,

Unfortunately, I think you're right and stated so further down in the
original posting. The problem is that idiots with no understanding of
the fundamentals stuff numbers into a simulator that may or may not
represent their actual implementation. They trust the result and have
no clue how to fix it if it doesn't work.

In skilled hands, a simulator with input that precisely models all the
circuit elements including parasitics, layout, power supply coupling
signal coupling, magnetic coupling, electrostatic coupling...the list is
long...can be a very powerful thing.

Anybody who starts their education with a simulator is doomed to failure.

not
> how we kid ourselves it is or should be. Yes, you need a good
> understanding independent of simulations, however, it is simple
> impossible to understand all of the nuances of a design without some
> constructive trial and error on a simulator. Yes, most don't like this
> idea, but it is the way it truly is. To illustrate. Consider the design
> of a nuclear bomb. These require amazingly powerful computers. Sure,
> they are run by *experts* , but even these 20 year experts cant
> understand the implications of all of the equations. Thery are simply
> too complicated. Or for example, colliding black holes. There is not a
> chance to develop a *feel* for happens *without* simulations.

Your argument is seriously flawed. Somebody sat down and scratched
their ass for a decade and decided, "Hey, I'll bet if we could split
an atom, we could get a LOT of energy...and we'd have to manage the
reaction somehow...and Uranium would be a good thing to look at...
let's go do some math.
You seem to be suggesting that any idiot with a big computer could
invent the bomb. NOT LIKELY! A simulator is pretty useless without
input. I'd go so far as to say that a simulator is pretty useless
with MOST unskilled input.

>
> Sure, I agree that without bench work there are many issues that one
> doesn't get a feel for in a simulator, but *likewise*, without a
> simulator there are *many more* things that you never get a feel for by
> bench work. As I said, I've been there 10000's of hours on both the
> bench and simulator. I can count countless things that I have missed on
> the bench that the simulator showed.
>
>
>>You have only to read the archives of this newsgroup to see countless
>>examples where people stuffed random numbers into a simulator and came
>>up with something that simulated, but was impractical, unrepeatable,
>>or just plain sad.
>
>
> But this is unintelligent trial and error. Intelligent trail and error
> is another matter entirely. *All* design can be reduced to a Darwinian
> process, i.g. replication of existing circuits, varying such designs,
> and selecting the good ones. Whether this is done on paper, in ones head
> (a Darwinian process) or on a simulator don't much matter.

I think you're exactly right. A designer without an understanding of
the fundamentals is gonna be just as bad whether he does simulation or
bench work.

>
>
> Kevin Aylward
> salesEXTRACT@anasoft.co.uk
> http://www.anasoft.co.uk
> SuperSpice, a very affordable Mixed-Mode
> Windows Simulator with Schematic Capture,
> Waveform Display, FFT's and Filter Design.
>
> 

-- 
Return address is VALID.
500MHz Tek DSOscilloscope TDS540 $2200
http://nm7u.tripod.com/homepage/te.html
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
http://www.geocities.com/SiliconValley/Monitor/4710/