SV: Re: [sdiy] Simulating SW?

[harrybissell]

Electronic Workbench "is" SPICE with a fancy wrapper.  If you dig beneath
the fancy oscilloscope (which is limited to two channels) you can get to
all spice functions. well not ALL, but all that existed way back then.

If you just push the "run" button the simulation is interactive, you could
put a pot in the circuit and move it in real time.

If you choose "transient analysis" (or just about any other analysis) you
have to set the initial conditions and can graph as many nodes as you like.

In some ways its a ideal program, simple enough to learn on (and it took me
maybe six months to learn the basics)... and then its a bridge to REAL spice.

One thing that is REALLY bad... it does not mix analog simulation and digital
simulation well at all.  Try having an analog circuit trigger a 4013 for
instance,
and you may work for days trying to get a real result.

In those cases, I say "fvck it" and go to the bench. I know by then it SHOULD
work so I make it so... :^P

For anyone new to simulation... PLEASE thake this advice. Run the simulation
AND build the circuit, and compare.  If they don't look alike, change the
simulation
models until it really works like the real thing. The biggest mistakes you can
make in
simulation is trusting the real world to work like the model. Sometimes SPICE
says
"it works" and it does not... other times it says it "doesn't work" and it
DOES. Only a
lot of experience can alert you to when you are being lied to.

I did a clamp circuit once... designed in SPICE. Then looking at it, I noticed
I had
made a current source feeding a current sink. I wondered "what would limit the

current in that case ???"   Answer, nothing. The standing current was a couple
of
kiloamps... from a 741 opamp.  Obviously a bad idea in real life, but the sim
looked
really good.  You might also find that a lot of models will allow you to apply
kilovolts
to the circuit.  The 741 (given the right supply voltages) can swing hundreds
of volts at the output.  LOL ... beware

H^) harry

karl dalen wrote:

> But you said SPICE simulation in the "pretender OVCO" thread!
> I tought you used SPICE? Wich one if you did?
>
> KD
>
> --- harrybissell <harrybissell at prodigy.net> skrev:
>
> > I use an old package called "Electronic Workbench". It is replaced by
> > "Multisim" and it is NOT student priced... :^(   It would probably be
> > $1000 - $1500 for a full package. Maybe $5K if you wanted to do PCBs etc
> >
> > in the same package. EWB has some minor bugs but if you have a Windoze
> > box you'd be used to that level of annoyance, anyway.
> >
> > Neat feature about EWB / Multisim... interactive on screen instruments
> > like
> > oscilloscopes, function generator etc. In most cases, no need to develop
> > your
> > own test sources.  This IS important... if you want a sine wave, fine
> > its there...
> > but there are no good SAWTOOTH waves and you WILL want those...
> >
> > There is a package called TINA that looks good.  There is a limited free
> >
> > version at Texas Instruments site called TINA-TI which is crippled by
> > number
> > of ICs and TI parts only (well, you'd figure that :^).  A full version
> > looks like
> > about $500 for the top of the line.
> >
> > I heartily do not recommend EDWin32. Bought it and its so buggy it was
> > totally useless to me.  You want free ??? contact me offlist.
> >
> > There is one called "Proton" by Labcenter (UK) that looks very nice. I
> > think
> > you can get a demo version to try before you buy.
> >
> > tom.adam at telenet.be wrote:
> >
> > > What simulation software you guys use for trying out new idea's?
> > > Or is this "not done".....
> > >
> > > Looking for a lite version, preferably freeware ;-)
> > >
> > > Cheers,
> > >
> > > --
> > > Tom Adam
> > > The Big Ear
> > > http://users.pandora.be/the-big-ear/
> > > Check out the download section!
> >
> >