Re: Is there a way to make node numbers appear on LTSpice schematics?
I can answer my own question: editing the plot.defs file *immediately* has effect.
(I reran the simulation before trying but did not restart LTspice.)
Why don't they document these useful enhancements? Is it in any of the LTspice
books or tutorials? I'm almost certain I tried this before with LTspiceIV and
it didn't work.
-marcel
|
Re: Is there a way to make node numbers appear on LTSpice schematics?
On Mon, Jul 17, 2023 at 02:33 PM, Andy I wrote: I do not think you can do that (except by defining functions in the waveform viewer).? Is it possible to use parameters and functions defined on the schematic (not in plot.defs) in the waveform viewer? Related, is it possible to use such parameters / functions in measurements, even when directly on a .raw file with a .meas script? I think this can be done with a dynamically adjusted plot.defs file, but currently that might need restarting the GUI. -marcel
|
Re: Is there a way to make node numbers appear on LTSpice schematics?
|
Re: Is there a way to make node numbers appear on LTSpice schematics?
What was the need for it, perhaps an alternative can be found. I think mousing over them is all you can do.
|
Re: Is there a way to make node numbers appear on LTSpice schematics?
Automatically assigned node numbers are ephemeral between runs, unless you label them.
Giving the same label to different nets, shorts those nets together. I use it often.
Giving more than one label to one net, confuses LTspice. I get no specific warning.
A short wire with label A at one end, and label B at the other, does NOT connect other nets A and B elsewhere on the schematic. It seems LTspice ignores some labels when another label has been found earlier on that net.
|
Re: Is there a way to make node numbers appear on LTSpice schematics?
Tony,
That is exactly what I was saying (or meant).
Andy
|
Re: Using Q=expr syntax in capacitor
George,
I don't think this can be called a bug.? Be aware that SPICE's (and LTspice's) netlist syntax is not free-form and we are not free to use functions anywhere we want to.? There are syntax rules, which can be tricky and difficult to understand.
I should preface this by saying that I don't have a lot of personal experience with LTspice's user-defined .FUNCtions.? Also, I don't know what was?your user-defined function, and more importantly, how you used it in your capacitor's Q=expression.
If you try to use a capacitor with something simple like Q=Myfunc(100p,5V)*x, LTspice gives an error and quits.? I think it makes sense that it would do that, because LTspice expects to see a number where "Myfunc(100p,5V)" is.? Enclose the function call between curly braces, like this: Q={Myfunc(100p,5V)}*x.? Note that only the function is in the curly braces; the special variable 'x' is outside.
Not knowing your function and what your Q=expr looks like, I can't say if this works for you.
But there might be another option.? Consider using a .TEXT definition, to shorten the appearance of a long expression on the schematic.? My understanding is that .TEXT uses a literal substitution of one string with another, before parsing the netlist and the syntax matters.
Andy
|
- Run LTspice
- Open Help (press F1, or go to Help > Help)
- Open the Contents
- Go to F.A.Q. > Simulating Transformers
To simulate any transformers in SPICE or LTspice using this linear transformer model, you need to know the primary and secondary inductances.? Well, you need to know at least one of them, and then you can calculate the other if you know the turns-ratio = voltage step-up or step-down ratio. Andy
|
The following formula can be used to calculate the dynamic resistance of a spark gap:
R = R0 * (1 - exp(-t / tau))
where:
??? R is the dynamic resistance of the spark gap at time t
??? R0 is the initial resistance of the spark gap (when t = 0)
??? tau is the time constant of the spark gap
The time constant of a spark gap for nitrogen at 1 atmosphere with a gap of 3mm is approximately 100 nanoseconds. This can be calculated using the following formula:
tau = 1.5 * d^2 / p * k
where:
??? tau is the time constant in nanoseconds
??? d is the gap spacing in millimeters
??? p is the gas pressure in atmospheres
??? k is a constant that depends on the gas composition
|
Re: ISL70444SEH declaration issue?
|
Re: Transformer models WAS: New Simulator Written by Mike Engelhardt
#Transformer
For those who are interested in modelling tube amplifiers and the output transformers used:?I have a thread on DIYaudio? with easy to use LTspice transformer models.
There are currently 3 flavours: Push-Pull with ultra-linear taps, Ditto with extra cathode feedback windings and Single-ended. I am working on a Hammond 125A. Just enter the numbers from the transformer datasheet. All tedious calculations are done by LTspice in the model.
Something like [Rpp=8k Lpp=1220 UL=35 Cp=390p Rp=152 RS4=0.145 K=0.9999987] for an AMPLIMO Toroidal Output Transformer type 20PP8K0S.
Comments are welcome,
Ite
|
Re: Using Q=expr syntax in capacitor
I realized it pretty quickly and remedied the problem.
?
|
Re: Transformer models WAS: New Simulator Written by Mike Engelhardt
#Transformer
This is a suspended thread, but
I am now able to look at the proposed tutorial The first
question is, what sort(s) of transformer? While the basic
theory is the same for all, the practical design methods vary
considerably. There is no point in writing a tutorial that
no-one is interested in.
I see the occasional query
about a power supply having a mains transformer with
inductances in the mH or less range, so there may be some
interest in mains transformers.? I also see the occasional
query about audio output transformers for tubes/valves.? I
don't think anyone would try to wind their own toroidal, so we
are talking 'E's and I's', maybe with the occasional 'T's and
U's.
I'm not going to deal with
transformers for SMPS, because they need a totally different
approach, as do RF transformers with ferrite cores or no core.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-04-29 19:50, Jim Wagner wrote:
toggle quoted message
Show quoted text
BUT, what are those “easily measured or calculated parameters”? I
am a circuit designer and have no idea what they are (or how to do
the measurements)!. I strongly suspect that I am not alone. How
about a tutorial for the wiki?
Jim
On Apr 29, 2023, at 11:06 AM, John Woodgate
< jmw@...>
wrote:
Many types of transformer do not need
complicated models like Gummel-Poon for
transistors, but of course complicated models like
Chan can give more accurate results (often more
accurate than is necessary, but that also apples
to transistor models, which do not account for
variations between samples). Simple models can use
easily measured or calculated parameters, so it is
easy to relate the model to the hardware.
Please note the new Subject line.
======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget. I see, and I remember. I do, and
I understand. Xunzi (340 - 245 BC)
On 2023-04-29 18:02, Jim
Wagner wrote:
For me. the real transformer challenge is associating
the physical parameters (dimensions, numbers of turns,
core material, and such) into model parameters. One
might reasonably assert that this is no different
than, say, transistors. There is a big difference,
though; I can build a transformer but I am not likely
to build a transistor. I do not have the capability to
measure transistors sufficiently to create models, so
must rely on third-parties to do that. What third
party do I use for that ferrite toroid transformer
that i just built?
Perhaps the solution to this is a
transformer model generator (like VDMOS tool). I can
handle program writing but I do not know enough
about magnetics to even think about something like
that. To be useful, such a model generator should
rely on measurements the most of us could do in a
modestly equipped lab (say, with a signal generator
and an oscilloscope).?
Jim Wagner
Oregon Research Electronics
Susan wrote, "My big
issue/stumbling-block when using 'spice
simulators is transformer models; they all
seem to be described in intractable terms
making it difficult to translate something I
have in my hand to an accurate simulation
model."
That sounds like a topic for a separate
subject (not this one).? The simplest
transformer models are very simple.? It's the
more complicated ones that can be challenging.
Andy
|
Re: Using Q=expr syntax in capacitor
Wrong thread, I think, Bruce.
--
Regards,
Tony
On 18/07/2023 15:19, BRUCE108 wrote:
toggle quoted message
Show quoted text
- Define the primary inductance as a parameter Lp
- Change the value of the primary inductor to {Lp}. the curly
braces will pick up the value of parameter Lp
- Define parameter n to be the turns ratio.
- Set the secondary inductance to be {n*n*Lp}
|
The inductance ratio is the squared of the winding ratio. If you need a 4:1 ratio for the windings. The Inductance shall have a 1:16 ratio. Ie. A 1 uH and a 16 uH inductor.?
Cheers! Bernie
hello sir, how can i set the total winding in trafo simulation? (flyback transformer)
|
- Define the primary inductance as a parameter Lp
- Change the value of the primary inductor to {Lp}. the curly braces will pick up the value of parameter Lp
- Define parameter n to be the turns ratio.
- Set the secondary inductance to be {n*n*Lp}
|
Re: Using Q=expr syntax in capacitor
Well, we can't tell for sure from the limited information you
supplied, but the Q function for a capacitor can only be an explicit
function of "x". "x" is the special variable for the voltage between
the "plates".
Help > LTspice XVII > LTspice? > Circuit Elements > C.
Capacitor:
Syntax: Cnnn n1 n2 Q=<expression>
[ic=<value>] [m=<value>]
There is a special variable, x, that means the voltage across the
device. Therefore, a 100pF constant capacitance can be written as
Cnnn n1 n2 Q=100p*x
You might want to refer to the group's files section where there a
number of examples of non-linear
capacitors.
--
Regards,
Tony
On 18/07/2023 14:07, George Yashin
wrote:
My question is
simple, and I think it is a bug:
When I use function that is defined by .func statement in
capacitor equation Q=func(args), I got the error that there is no
such function.
But it is perfectly works in behavioural sources. If I enter
equation directly in capacitor, it works.
What is the reason for that?
|
Using Q=expr syntax in capacitor
Hello,
My question is simple, and I think it is a bug:
When I use function that is defined by .func statement in capacitor equation Q=func(args), I got the error that there is no such function.
But it is perfectly works in behavioural sources. If I enter equation directly in capacitor, it works.
What is the reason for that?
Thank you in advance
|
With that level of input data,
the answer is 'make it about enough'.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
toggle quoted message
Show quoted text
hello sir, how can i set the total winding in trafo simulation?
(flyback transformer)
|
hello sir, how can i set the total winding in trafo simulation? (flyback transformer)
|
John Woodgate
Tony Casey