I haven't seen any noise waveforms, but that doesn't mean it's not there!
What sort of name should I be looking for?

I can see how the oscillator suggestion could work, but the other stuff is way
too advanced for me - a total of about 2 hours playing with it so far!

Is there a web site which gives additional component libraries?  eg. I'd like
to use BC107B and LM317LZ

Regards,
Mark



> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu]On Behalf
> Of Rob Young
> Sent: 24 November 2004 14:17
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE]PSPICE help
> 
> 
> > I've downloaded the free 'student' version, and I have a 
> question.  I 
> > managed
> > to suss out how to model a switch opening or closing after 
> a period of 
> > time,
> > but is it possible to model a 'noisy' switch change at all?
> >
> > Also, PSPICE to me so far seems very good for modelling 
> individual little
> > modules, but I'm not sure how I'd go about drawing the 
> schematic for my 
> > whole
> > project, ready to feed in to something to lay out a PCB - 
> how can I put in
> > place a dumb 16/18pin IC to represent a PIC or any other IC 
> not in the
> > library?  or a connector strip, ICP programming header?
> >
> > Am I using the wrong tool for what I need?
> >
> > Regards,
> > Mark
> >
> >
> 
> You can model your "noisy" switch a few different ways:
> 
> 1) Add additional resistance to the model (I'm assuming you 
> are using the 
> voltage controlled switch or current controlled switch).  You 
> can use the 
> built-in parameter or add your own to the net list to 
> simulate cross-talk.
> 2) Add external capacitance to the net list, also inductance 
> to simulate 
> leads, etc.
> 3) Drive the switch with a pulse or custom waveform to make 
> it "chatter" (ie 
> contact bounce of  a mechanical switch or relay)
> 4) Some versions of spice include a "noise" waveform, don't 
> know about the 
> student edition of Pspice.  That could be "injected" on 
> either side of the 
> switch through a capacitor.
> 5) Some versions of spice include "noise" analysis where the 
> Johnson noise 
> of resistors is included.
> 
> As far as having a tool for doing schematics and small 
> layouts, Eagle has a 
> "free" version and various levels of "paid" versions 
> depending on what you 
> need.
> 
> There have been numerous threads on PicList about CAD 
> software so perhaps 
> the archive can disgorge some information for you.  Otherwise 
> you could 
> start a weekend CAD-religion war and see what kind of 
> responses you get... 
> :-)
> 
> Rob Young
> _______________________________________________
> http://www.piclist.com PIC/SX FAQ & list archive
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> 

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