Glen, to be honest, I am not very optimistic about doing
simulation. Too many unknowns and fudge factors. Plus, it is too easy
to make a mistake and simulate something that's not related to what my
circuit will be doing.
I think you are overestimating the difficulties and underestimating
the value of Spice simulations. True, simulations can lie, but you
will be testing your circuit at low power and you can obtain some
confidence in your spice simulation by verifying that it predicts the
low power operation of your circuit, then simulate full power, then
build the full power version.
What I would like to do is find some way to actually measure the peak
voltages ad dV/dt and such. Any suggestions for doing so, given that
I own a Tek 2445 scope?
This would be easier with a digital or storage scope in the situation
where you are producing only a single event. In the old days before
the invention of digital and storage scopes we used Polaroid
oscilloscope cameras to capture single shots; they mounted on the
scope faceplate with an adapter that excluded room light. The shutter
was opened, the event being observed fired and the scope triggered
from it, camera shutter closed and then film developed. I don't know
if any cheap digital cameras have a time exposure mode, but if so you
could rig one up to do this.
But for low power testing you just repeat the event at some regular
rate and trigger on it.
Of course a Spice simulation lets you "scope" any current or voltage
in the circuit, and tweak until you like the results. No parts need
to be replaced when their ratings are exceeded either.
Also, did you see my posts about getting the timing/duty cycle circuit
to work. It works now...
No, I missed it, I mostly just scan subject lines and read a few
messages on interesting topics, like welding. (I paid for a good part
of my engineering degree by pushing puddles of metal around.) I trust
you have a means for adjusting phase overlap? Why not simulate your
working circuit to gain some experience and confidence in Spice?
-----------
OT - a spice story:
A few years ago, when DOS 3.2 was mickeysofts latest and greatest, I
bought the "free" student version of PSpice (with the $100 manual,
good luck using it without the manual). Entirely text based, no
schematic capture, much harder to use than LTSpice. Right after I
read the manual a Co-Op student walked into my office and complained
that a customer had provided an erroneous schematic for an
overtemperature shutdown board they wanted us to reproduce since the
OEM was out of business and their stock system was out of them. The
student had figured out what was wrong with their schematic and fixed
it, but the customer refused to accept the change, insisting that they
had provided a certified drawing which could not be wrong, we must
have made a mistake and we should fix our mistake not change the
drawing. The student wanted me to call the customer and straighten
him out, but instead I handed him my copy of PSpice and told him to
simulate the circuit both ways. The customer dosen't accept the
evidence, provide him with more evidence. "SPICE" he complained, "I
don't know SPICE! I can't do that!" Sure you can, I said, providing a
5-minute tutorial, and instructing him to try out all of the available
reports.
The next day he returned with an inch thick dot-matrix printout on
wide paper, which exactly duplicated both his pencil and paper
analysis and the actual circuit operation. After I convinced him that
rolling up the printout and beating the customer severely about the
head and shoulders with it could be bad for repeat business, he sent
the printout to the customer, with circles, arrows and post-it notes
identifying the important parts. The customer then accepted the
change and agreed to pay for it.
Next time I saw the customer I asked if he had changed his drawing.
"Are you KIDDING? Do you know how hard it is to change a CERTIFIED
DRAWING? I don't have that kind of time!" was his unsuprising
response. But the Co-Op student gained some valuable experience, and
has been a Spice advocate ever since.
Try it, you'll like it
.
