SWCAD III - plotting waveform

[Terry Pinnell]

My investement in CircuitMaker is substantial, over years, and it has
many features I like (including its extensive library). So I'd
probably never willingly abandon it. But it's clear that
LTspice/SwitcherCAD III has many strengths (including its support
here), so I've recently returned to it to experiment a little.

Could one of the LTspice experts advise me on a small initial query
please. After drawing a simple schematic I plotted the waveform at a
test node. But how do I place permanent probe symbols on the schematic
please, so that I can immediately visually relate the waveform to the
nodes being plotted?

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[Terry Pinnell]

"Mike Engelhardt" <pmte@concentric.net> wrote:

Terry,

Could one of the LTspice experts advise me on a small initial query
please. After drawing a simple schematic I plotted the waveform at a
test node. But how do I place permanent probe symbols on the schematic
please, so that I can immediately visually relate the waveform to the
nodes being plotted?

There's really no need for test points in LTspice since anything
can be plotted. As you move the mouse around, the mouse cursor
turns into a voltage probe when you're pointing at a plotable
voltage and it turns into a current probe when you pointing at
a plotable current. But you can label nets so that those net
names don't change between schematic edits(Edit=>Label Net).
Then, if you wish, after you plot the trace the first time,
you can save the plot setup. If you save it under the default
name generated for that schematic, then when you come back to
that schematic the next day the initial plot will come up with
those traces.

Thanks Mike. But what I'm trying to do is create the same kind of
screenshots I do at present with CM. Here's a recent example:
http://www.terrypin.dial.pipex.com/Images/JFTimerSim.gif

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[Mike Engelhardt]

Terry,

Could one of the LTspice experts advise me on a small initial query
please. After drawing a simple schematic I plotted the waveform at a
test node. But how do I place permanent probe symbols on the schematic
please, so that I can immediately visually relate the waveform to the
nodes being plotted?

There's really no need for test points in LTspice since anything
can be plotted. As you move the mouse around, the mouse cursor
turns into a voltage probe when you're pointing at a plotable
voltage and it turns into a current probe when you pointing at
a plotable current. But you can label nets so that those net
names don't change between schematic edits(Edit=>Label Net).
Then, if you wish, after you plot the trace the first time,
you can save the plot setup. If you save it under the default
name generated for that schematic, then when you come back to
that schematic the next day the initial plot will come up with
those traces.

--Mike

 

[Mike Engelhardt]

Terry,

Thanks Mike. But what I'm trying to do is create the same
kind of screenshots I do at present with CM. Here's a
recent example

Okay, then label the nets A, B, C, D, E, F and plot them.
You can also put them each in there own plotting pane.
You can put the two files below, a.asc and a.plt, in the
same directory and then open and run a.asc.

--Mike

--- a.asc ---
Version 4
SHEET 1 888 1240
WIRE -560 976 -560 848
WIRE -560 848 -480 848
WIRE -480 848 -480 896
WIRE -560 848 -560 832
WIRE -224 896 -224 848
WIRE -224 848 -96 848
WIRE -96 848 -96 832
WIRE -96 848 -96 976
WIRE -480 976 -480 1024
WIRE -480 1024 -496 1024
WIRE -224 976 -224 1024
WIRE -224 1024 -176 1024
WIRE -432 1024 -448 1024
WIRE -240 1024 -224 1024
WIRE -368 1024 -304 848
WIRE -304 848 -256 848
WIRE -304 1024 -368 848
WIRE -368 848 -400 848
WIRE -560 1072 -560 1104
WIRE -96 1072 -96 1104
WIRE -720 1104 -720 944
WIRE -720 864 -720 720
WIRE -720 720 -560 720
WIRE -560 720 -560 752
WIRE -560 720 -96 720
WIRE -96 720 -96 752
WIRE -400 848 -480 848
WIRE -256 848 -224 848
WIRE -448 1024 -480 1024
WIRE -176 1024 -160 1024
FLAG -96 1104 GND
FLAG -560 1104 GND
FLAG -720 1104 GND
FLAG -400 848 A
FLAG -256 848 B
FLAG -448 1024 C
FLAG -176 1024 D
SYMBOL RES -576 736 R0
SYMATTR InstName R1
SYMATTR Value 2K
SYMBOL res -112 736 R0
SYMATTR InstName R2
SYMATTR Value 2K
SYMBOL res -496 880 R0
SYMATTR InstName R3
SYMATTR Value 101K
SYMBOL res -240 880 R0
SYMATTR InstName R4
SYMATTR Value 100K
SYMBOL cap -368 1008 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value .01ľ
SYMBOL cap -240 1008 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C2
SYMATTR Value .01ľ
SYMBOL VOLTAGE -720 848 R0
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL NPN -160 976 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL npn -496 976 M0
SYMATTR InstName Q2
SYMATTR Value 2N3904
TEXT -440 1112 Left 0 !.tran 25m startup

--- a.plt ---
[Transient Analysis]
{
Npanes: 4
Active Pane: 3
{
traces: 1 {524293,0,"V(d)"}
X: ('m',0,0,0.002,0.025)
Y[0]: (' ',1,-4.5,0.5,1)
Y[1]: ('_',0,1e+308,0,-1e+308)
Volts: (' ',0,0,1,-4.5,0.5,1)
Log: 0 0 0
GridStyle: 1
},
{
traces: 1 {268959748,0,"V(c)"}
X: ('m',0,0,0.002,0.025)
Y[0]: (' ',1,-4.5,0.5,1)
Y[1]: ('_',0,1e+308,0,-1e+308)
Volts: (' ',0,0,1,-4.5,0.5,1)
Log: 0 0 0
GridStyle: 1
},
{
traces: 1 {268959747,0,"V(b)"}
X: ('m',0,0,0.002,0.025)
Y[0]: (' ',1,-0.5,0.5,5)
Y[1]: ('_',0,1e+308,0,-1e+308)
Volts: (' ',0,0,1,-0.5,0.5,5)
Log: 0 0 0
GridStyle: 1
},
{
traces: 1 {268959746,0,"V(a)"}
X: ('m',0,0,0.002,0.025)
Y[0]: (' ',1,0,0.5,5)
Y[1]: ('_',0,1e+308,0,-1e+308)
Volts: (' ',0,0,1,0,0.5,5)
Log: 0 0 0
GridStyle: 1
}
}

 

[Terry Pinnell]

"Mike Engelhardt" <pmte@concentric.net> wrote:

Terry,

Thanks Mike. But what I'm trying to do is create the same
kind of screenshots I do at present with CM. Here's a
recent example

Okay, then label the nets A, B, C, D, E, F and plot them.
You can also put them each in there own plotting pane.
You can put the two files below, a.asc and a.plt, in the
same directory and then open and run a.asc.

Many thanks for the prompt follow-up, Mike. Now understood.

BTW, why do you call that dialog window 'Net Name' rather than 'Node
name'?

Just to be sure I have it right, this is now the procedure I'm
following to add node labels.
1. Display the schematic.
3. Decide which nodes I want to label.
3. Use Edit=>Label Net (or F4) to bring up the 'Net Name' dialog
4. Enter the name, click OK.
5. Drag the symbol to the correct location, left click to place it,
then r-click. (BTW, the prog lets me place it *anywhere*, not
necessarily on a node. Is that deliberate?)
6. Repeat that for each node I want to see on my schematic
7. Simulate, and choose *my* node names instead of default names;
these will then appear on both schematic and plot. (If I've already
displayed a plot, with some default-named labels, how do I quickly
re-run it so that *my* labels are now used?)

But, assuming I'm happy with the *default* node names, can I get SWCAD
III to simply place those on the schematic *automatically*?

That's what CM does. Actually, to minimise clutter, it places node
*abbreviations* (A, B, C etc), and colour codes them for added
visibility, as you see in that same example:
http://www.terrypin.dial.pipex.com/Images/JFTimerSim.gif

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[Mike Engelhardt]

Terry,

BTW, why do you call that dialog window 'Net Name' rather
than 'Node name'?

I don't know of an authoritative source on the difference
between the two, but I think of a node as point in a circuit
with an absolutely unique voltage and net as the collection
of all component connections touching the same node. By that
convention, node would be clearer from a math point of view
since everything on a net is assumed to be a single node, but
I hear "net" more often than "node" in this context, as in
"netlist". I've never heard of a "nodelist".

5. Drag the symbol to the correct location, left click to
place it, then r-click. (BTW, the prog lets me place it
*anywhere*, not necessarily on a node. Is that deliberate?)

Sure you may want to place a net before hooking the wires
up to it. The labeled net might be port to a different
level of the hierarchy.

7. Simulate, and choose *my* node names instead of default names;
these will then appear on both schematic and plot. (If I've already
displayed a plot, with some default-named labels, how do I quickly
re-run it so that *my* labels are now used?)

When you re-run, the new plot will have the same data traces plotted
as the one before re-running. Except if a trace uses a node that
no longer exists, then the trace is deleted.

But, assuming I'm happy with the *default* node names, can I get
SWCAD III to simply place those on the schematic *automatically*?

No, you have to position them, since they could be placed anywhere
on the net for the same meaning.

That's what CM does. Actually, to minimise clutter, it places
node *abbreviations* (A, B, C etc), and colour codes them for
added visibility, as you see in that same example:
http://www.terrypin.dial.pipex.com/Images/JFTimerSim.gif

The problem with abbreviations is that you now have two names for
the same net and that messes up plotting expressions of data. Say
you have an abbreviation B for node buf1 and also node B. Now you
want to plot the quantity "pow(V(B),3)-V(n001)". Is V(B) node B
or buf1? Even though the program can handle the confusion,
abbreviations for node names is not a practice I recommend.

--Mike