Question - what is the internal modelling technique used
by these various programs, and can we produce our own package?

Is it based upon successive delta-time increments, and if so, what
is the increment? What prompted the last question is an attempt
I made to create a sine-wave generator using the identity that
sin dTheta = dTheta, but I had to go for an _extremely_ small
value of dTheta (ISTR 10^ -18) before getting anything like a
decent sine wave, and even that degenerated after a few cycles.

So, these circuit simulators - what is their underlying technique
for circuit simulation?

"Roger Johansson" wrote in message
...
"Reg Edwards" wrote:
Some years back, after retirement, I bought out of curiosity a copy of
Electronics Work Bench. It was and still is the only such program I
have ever had my hands on. I think it arrived on a collection of
floppies.
Multisim has a very bad reputation because is has a lot of bugs.
The best version of EWB is 5.c

On Sun, 17 Oct 2004 13:52:17 +0100, "Airy R. Bean"
wrote:

Question - what is the internal modelling technique used
by these various programs, and can we produce our own package?

Most of them (exceptions being the harmonic balance types for RF) use
the old Berkeley Spice engine developed by the good folks at the
eponymous university. The simulation package authors just adapt the
engine with their own preferences WRT to features, GUI, gimmicks etc.
So yeah, you can certainly come up with your own flavor of Spice just
by adapting the basic Berkeley engine to your tastes. It's highly
unlikely to be worth the effort, though. There's already a spice out
there for everyone - if you can find the right one for you.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

On Sun, 17 Oct 2004 05:59:02 +0000 (UTC), "Reg Edwards"
wrote:

Some years back, after retirement, I bought out of curiosity a copy of
Electronics Work Bench. It was and still is the only such program I have
ever had my hands on. I think it arrived on a collection of floppies.

After a few days curiosity was satisfied. Then I junked it.
---
Reg

In 1970 I bought the latest issue RSGB Handbook, obviously a decade
before the transistors were being discovered in England, and several
decades before the spectrum analyser were applied over there. So after
a week I managed to find another person to keep the book, not sure if
he paid for the rubbish

73, Jan-Martin
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

I'm not interested in someone else's engine - that's not the
way of the _REAL_ Radio Ham

It is _ALWAYS_ worth the effort to do things for yourself - that
is the essence of _REAL_ Ham Radio - it is the CBer and the
CBer-Masquerading-As-A-Radio-Ham who buy things
off-the -shelf!

"Paul Burridge" wrote in message
...
On Sun, 17 Oct 2004 13:52:17 +0100, "Airy R. Bean"
wrote:

Question - what is the internal modelling technique used
by these various programs, and can we produce our own package?

Most of them (exceptions being the harmonic balance types for RF) use
the old Berkeley Spice engine developed by the good folks at the
eponymous university. The simulation package authors just adapt the
engine with their own preferences WRT to features, GUI, gimmicks etc.
So yeah, you can certainly come up with your own flavor of Spice just
by adapting the basic Berkeley engine to your tastes. It's highly
unlikely to be worth the effort, though. There's already a spice out
there for everyone - if you can find the right one for you.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

It's been the case in Britland for many years now, that if you
want info to build modern gear, then buy the ARRL handbooks.
OTOH, if you want a mediocre book that is many
years out of date and seems to owe more to self-congratulation than
it does to technical excellence, then go for the RSCB offering. Odd, really,
when you consider that the RSCB is a publishing corporation.

"J M Noeding" wrote in message
...
In 1970 I bought the latest issue RSGB Handbook, obviously a decade
before the transistors were being discovered in England, and several
decades before the spectrum analyser were applied over there. So after
a week I managed to find another person to keep the book, not sure if
he paid for the rubbish

On Sun, 17 Oct 2004 15:00:49 +0100, "Airy R. Bean"
wrote:

It's been the case in Britland for many years now, that if you
want info to build modern gear, then buy the ARRL handbooks.
OTOH, if you want a mediocre book that is many
years out of date and seems to owe more to self-congratulation than
it does to technical excellence, then go for the RSCB offering. Odd, really,
when you consider that the RSCB is a publishing corporation.

I do not agree, and soon the RSGB is the only IARU organization I
support, have been a member from january 74. They now contribute with
a lot of useful material, but it was different earlier, as one had the
feeling that high-ranked persons or duke and knights with outdated
experience was telling you what to do.

But for Radcom, I must admit that I mainly read G3VA's "Technical
topics"

My radio club was Worcester &DARC, suppose it is not so much activity
there now....

---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

Roy Lewallen wrote:
(In
fact, recognizing it value, Tek spent a large amount of money and
devoted resources to development of its own internal version of SPICE,
which included schematic entry and other features before they were
available in outside commercial versions.)

You owe me a keyboard to replace the one that just died under three
quarts of drool.

--
Most dying mothers say, "I love you, son," or "Take care of your sister."
Why were the last words of Kerry's mother a lecture on integrity?

On Sun, 17 Oct 2004 16:52:38 +0200, J M Noeding
wrote:

On Sun, 17 Oct 2004 15:00:49 +0100, "Airy R. Bean"
wrote:

It's been the case in Britland for many years now, that if you
want info to build modern gear, then buy the ARRL handbooks.
OTOH, if you want a mediocre book that is many
years out of date and seems to owe more to self-congratulation than
it does to technical excellence, then go for the RSCB offering. Odd, really,
when you consider that the RSCB is a publishing corporation.

I do not agree, and soon the RSGB is the only IARU organization I
support, have been a member from january 74. They now contribute with
a lot of useful material, but it was different earlier, as one had the
feeling that high-ranked persons or duke and knights with outdated
experience was telling you what to do.

But for Radcom, I must admit that I mainly read G3VA's "Technical
topics"

My radio club was Worcester &DARC, suppose it is not so much activity
there now...

In my limited experience over the lats 22 months Iv'e read both (well
looked through both!) and they aer both highly infromative books. Id
just give the edge to the ARRL version, it's more readable and has
more coentent, but hte RAdcom version is still well worlth having on
the shelf. I do'nt see any problem with the Brits anachronistic
attachment to valve gear.
--

Fat, sugar, salt, beer: the four essentials for a healthy diet.

On Sun, 17 Oct 2004 23:07:14 GMT, Steve Evans
wrote:



In my limited experience over the lats 22 months Iv'e read both (well
looked through both!) and they aer both highly infromative books. Id
just give the edge to the ARRL version, it's more readable and has
more coentent, but hte RAdcom version is still well worlth having on
the shelf. I do'nt see any problem with the Brits anachronistic
attachment to valve gear.

I is really a myth, TV sets were fully transistorized in Europe
compared to USA by several years


---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

"Airy R. Bean" wrote in message
...
I'm not interested in someone else's engine - that's not the
way of the _REAL_ Radio Ham

It is _ALWAYS_ worth the effort to do things for yourself - that
is the essence of _REAL_ Ham Radio - it is the CBer and the
CBer-Masquerading-As-A-Radio-Ham who buy things
off-the -shelf!

"Paul Burridge" wrote in message
...
On Sun, 17 Oct 2004 13:52:17 +0100, "Airy R. Bean"
wrote:

Question - what is the internal modelling technique used
by these various programs, and can we produce our own package?

Steve (Evans),
Correct me if I am wrong (like I need to say this here, eh?)
I believe the underlying basis is the collection of loop / node equations
used (by Engineers) to model circuits. We know the behavior of resistors,
inductors and capacitors and have mathematical models for them. To this we
add the active devices, etc. and develop an "engine" which does all the
calculations for us. [[we used to do them by hand/slide rule -- yes, I am
included in this we]]. These loop and node equations provide us with a
mathematical model of the behavior of electronic circuits. If done
carefully, this is a general purpose model which applies to all the
situations for which our component models are valid.
Some time later there were bare engines into which we had to type the part
values and node numbers (the sane things you can see in printouts from
Spice). As computers got more powerful, schematic entry was developed. I
believe these programs to be very useful, but as with any model or
simulation, it is best to understand the limitations.
Thre is an alternate method. It is also possible to derive equations for
each type of situation and use these calculations each time you need to
solve that type of problem. I am sure you are familiar with the equations
for things such as parallel capacitors and resonance and so forth. These
are specific solutions of the properties of components in those specific
circuits.
From some postings here I get the idea that Reg is providing various
"calculators" in the form of computer programs for hams to use to
solve/design various circuits. Not one thing wrong with either this or the
general type of software...Except that the limitations argument applies to
all calculations and it is our responsibility to determine whether or not
our situation is adequately covered by a particular math model.
I am also not familiar with the programs mentioned here (except to have
heard the names), except for OrCad's PSpice ver 9, which is relatively easy
to use (for me) and provides results adequate for my purposes--not to
mention the fact that I was given a CD with the student sample version on
it). I was introduced to is by the department chair at the county college
where I was asked to teach some classes and like it. I just draw a circuit
and can then do various forms of analysis. I modeled a recent project and
all worked the first time when I assembled the one and only unit. It was a
simple RS-232 to Kenwood TH-F6A handheld interface.

I agree 100% with Reg in that a circuit simulation program is not intended
to *teach* circuit theory, That needs to come first, then the simulation
tool can help us gain a better understanding by letting us try out the
things we learn and "see" them happen with out having to collect all the
parts and wire it up. I find it much faster to "assemble" a PSpice circuit
and test my design ideas than go into my basement and collecting all the
parts.

BTW it *IS* the cap AND diode which cause the negative voltage in the
coupling circuit described so long ago...

Airy,
While I applaud your desire to understand how these "engines" work and
perhaps build your own, I suggest that it is a most formidable task by any
measure. If you understand the concept of loop and node equations then you
know the math. Now figure out how to write software to handle any circuit
and you have it...then there is the user interface...(what I believe is the
most important [and most difficult to do well] part of any program)

73,
--
Steve N, K,9;d, c. i My email has no u's.