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--- In LTspice@..., Helmut Sennewald wrote:

We shouldn't attack users when we don't know about their
knowledge and capabilities. Please keep that in mind.

Hello Helmut,

I think you have mistakenly interpreted my response as an attack
when it was not. In fact, a reading or comprehension problem was
one of several reasonable possibilities to ask about, given that
the original poster claimed to have read the Help topic on the
switch element, yet was unable to see that it clearly stated the
he must provide a model statement.

This section of the Help topic is very short and includes a clear
link to an example schematic, something that would have answered
his questions. Yet for some reason, he did not run the example.
I truly would like to know the reason why not (and why so many
other people seem to have trouble with Help). This really is a
puzzle to me.

I am gradually coming to the conclusion that written words, even
if short and simple, are not always "seen." It may be because
the reader is not a native speaker of English, it may be because
they are faced with an information overload, or it may be that
the "Twitter" generation can't always effectively process
traditional "dry" textbook-style information (i.e., a reading
comprehension problem), or it may be simple laziness (which, I
suppose a person has the right to be - as long as they don't try
to steal the labor of others).

Anyway, I wonder if Help would be more effective if it included
graphical examples or at least hot links to graphical examples
or hotlinks to launch example schematics. The question remains:

How to make Help continue to function as a compact and efficient
reference while also being able to effectively provide answers
that neophytes can actually see, process and put to use?

Regards -- analogspiceman

In message <4E736E3F.4040008@...>, dated Fri, 16 Sep 2011, Bhakakhan <bhakakhan@...> writes:

Indeed, we should attack users, who attack users - it seems that this is the only language, those pseudo-masters will understand.

Johannes Herrmann / Yahoo Micbuilders Group

P.S. In our group, such an incident is unthinkable. that'll be worth a strike.

On the other hand, is a 'me too' post to a moderator's post in any way helpful? Isn't it liable to make things worse?
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

I need to model the coupling coefficient of two inductors as a function of time. I tried using combination of .func and .param statements to pass a time varying variable to the spice K component without success. I also have tried the trick used for defining a time varying resistor using a voltage of a node in the schematic.

Any suggestion would be greatly appreciated.

tony

I think a distinction needs to be made between attacking the issue and
attacking the user..
Cheers
AG

Indeed, we should attack users, who attack users - it seems that this
is the only language, those pseudo-masters will understand.

Johannes Herrmann / Yahoo Micbuilders Group

P.S. In our group, such an incident is unthinkable. that'll be worth a
strike.

best regards...

The "Pick New Transistor" function is wonderful, allowing me to sort by key features for an easy selection of the available library of parts. Is there any way to access a selector menu like this for the wide selection of LT opamps? I really want to use LT opamps in my current design, but I'm getting tired of going up to the LT site and using their feature selection tool to find an appropriate opamp. If I think I need an amplifier with a faster slew rate to solve my immediate problem, it would be nice to get into the LTspice opamp selection menu, sort by slew rate, then select a device that has the proper range of features. I often find myself running simulations in places where I don't have access to the LT website, so this feature would be really nice to have. Is it already there and I just don't know about it?

--- In LTspice@..., "analogspiceman" <analogspiceman@...> wrote:

--- In LTspice@..., Michael Stuarts wrote:

The model for SW appears to missing. If anyone can help me
create a .model statement for schematic that would be great.
I could not figure out how to do it from the help file alone.

Why not? Do you have a reading comprehension problem?

Hello analogspiceman and all others,

We shouldn't attack users when we don't know about their
knowledge and capabilities. Please keep that in mind.

Best regards,
Helmut
Moderator

PS:
Especially using the switch sw is often the first time
where a new user has to define a model.

Tony

You should have taken the hint by now that my query on modelling frequency dependence was done in total oblivion of Shivesh's original thread over which for some reason you keen wanting to remind me about. Shivesh's several specfiic replies have been infinitely more helpful and constructive...

George

_____

From: Tony Casey [mailto:tony@...]
To: LTspice@...
Sent: Fri, 16 Sep 2011 12:08:42 +0100
Subject: [LTspice] Re: Freqeucny Dependent resistor






<snip>
--- In LTspice@..., "George Evans" <george.evans@...> wrote:

Guys all this is first year circuit theory. We all know and come across series to paarllel convertions of reactive networks that introduce FDR effects where the real part of the immitance function varies with freq and these are LINEAR circuits. And as no real device is devoid of inductive/capacitive parasitics ,no matter how small, freq dependancy should not be a mistery.

Nonlinear effects were the reason I started this thread for modeling such things as ferrite cores. Manufactures rountinely supply spice parameters for these devices which involve freq dependant effects related to nonlinear loss mechanisms ( hysterisis etc ) .
George

</snip>
George,

It's no more trivial than referring to the help file to find the correct syntax for using Laplace in dependent sources, which was the subject of your original question in this thread, which as far as I can determine, was actually started by Shivesh.

Regards,
Tony








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--- In LTspice@..., "Tony Casey" <tony@...> wrote:

<snip>

However some transient simulations take 20-30 minutes to run, and when you reload the plot settings, it gets rid of the cursors. Plus every 5-10 seconds, the plot re-autoscales as more results are added to it. I am having a fighting battle. I have also considered using min/max, but I like the scales I've chosen with 55V on the left and 550A on the right, and I'm not sure I'd get them to match as nicely.

I really want to rant, and I'm sure I want to connect someone to the output of the power supply, but to be honest, I am so thankful for LT Spice that I can only manage "Thank you Mike" :)

</snip>
Hello Alan,

Part of your problem can be sorted by disabling marching waves, either from the Simulation menu, or by adding:
.option nomarch
in the schematic. This speeds up long .tran simulations considerably.

Regards,
Tony

I mean the "View>Marching Waves" menu.

<snip>

However some transient simulations take 20-30 minutes to run, and when you reload the plot settings, it gets rid of the cursors. Plus every 5-10 seconds, the plot re-autoscales as more results are added to it. I am having a fighting battle. I have also considered using min/max, but I like the scales I've chosen with 55V on the left and 550A on the right, and I'm not sure I'd get them to match as nicely.

I really want to rant, and I'm sure I want to connect someone to the output of the power supply, but to be honest, I am so thankful for LT Spice that I can only manage "Thank you Mike" :)

</snip>
Hello Alan,

Part of your problem can be sorted by disabling marching waves, either from the Simulation menu, or by adding:
.option nomarch
in the schematic. This speeds up long .tran simulations considerably.

Regards,
Tony

In message <4E733CC9.9050803@...>, dated Fri, 16 Sep 2011, ehydra <ehydra@...> writes:

But for what is the option to disable auto-scale in the menues good for? I cannot figure it out.

It puzzles me, too.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

On Fri, 16 Sep 2011 08:34:50 +0100, you wrote:

-----Original Message-----
From: LTspice@...
[mailto:LTspice@...] On Behalf Of John Fields
Sent: 16 September 2011 00:38
To: LTspice@...
Subject: Re: [LTspice] Re: Freqeucny Dependent resistor


On Thu, 15 Sep 2011 13:20:01 -0700, you wrote:

I believe it is impossible to have a physically realizable

resistor that is frequency >dependent and has no reactive component.

---
Carbon button microphone?

Well as that has a "?" I suppose its worth treating as a question, but I
guess its tongue in cheek. Its not frequency dependant as such, merely
pressure dependant.

---
As the frequency of the pressure wave increases, the corresponding
change in resistance will decrease.

Sorry I brought it up though, since it's really off-topic here.

It's on-topic at sci.electronics.design, if you'd like to continue.

--
JF

John Woodgate schrieb:

If you follow Helmut's advice and add constant voltage and current traces before you save the plot settings file, I think the problems you report do not occur.

But for what is the option to disable auto-scale in the menues good for? I cannot figure it out.

Hm.

- Henry

--
ehydra.dyndns.info

In message <j4v5a8+rsrc@...>, dated Fri, 16 Sep 2011, Alan <Yahoo@...> writes:

That is true, and I have defined the space-bar to reload the settings, so it behaves similar to in the schematic editor. I have set the scales to make it easy to compare the voltages/currents in my converters.

If you follow Helmut's advice and add constant voltage and current traces before you save the plot settings file, I think the problems you report do not occur.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

Hi there,

as already posted by Helmut a while ago, Mike Engelhardt will come over to Germany to enlighten us on his LTSpice IV world tour. Although Stuttgart and Hannover are fully booked there are a few seats left in Duesseldorf, Tuesday the 27th of September. So take your chance to get first hand information from the chief himself and register at www.setron.de. The seminar is free of charge and will start 9:30AM,end time shall be 4PM and when I am informed correctly there is no lunch box necessary.

Take your chance
Bernd

<snip>
--- In LTspice@..., "George Evans" <george.evans@...> wrote:

Guys all this is first year circuit theory. We all know and come across series to paarllel convertions of reactive networks that introduce FDR effects where the real part of the immitance function varies with freq and these are LINEAR circuits. And as no real device is devoid of inductive/capacitive parasitics ,no matter how small, freq dependancy should not be a mistery.

Nonlinear effects were the reason I started this thread for modeling such things as ferrite cores. Manufactures rountinely supply spice parameters for these devices which involve freq dependant effects related to nonlinear loss mechanisms ( hysterisis etc ) .
George

</snip>
George,

It's no more trivial than referring to the help file to find the correct syntax for using Laplace in dependent sources, which was the subject of your original question in this thread, which as far as I can determine, was actually started by Shivesh.

Regards,
Tony

--- In LTspice@..., "pindsen" <windven@...> wrote:

--- In LTspice@..., "Helmut" <helmutsennewald@> wrote:

--- In LTspice@..., "pindsen" <windven@> wrote:

Hi,

I need an BSS138 in my LTSpice simulation.
Since I can't find that component in the program itself, I need to make it.

I have done the following steps but LTspice won't simulate:

1) Downloaded a Zetex BSS138 spice subcircuit and placed it in a "BSS138.sub" file
2) The spice file is placed in c:&#92;program files&#92;LTC&#92;LTspiceIV&#92;lib&#92;sub
3) Included a nmos symbol (nmos.asy) in the design
4) Renamed the symbol to BSS138/ZTX
5) Add a spice directive command ".inc BSS138.sub"
6) Hit the run button
7) LTspice can't simulate and says "Can't find definition of model "bss138".

The Zetex spice model can be seen here:

*ZETEX BSS138 Spice Mosfet Subcircuit Last revision 11/91
*
.SUBCKT BSS138/ZTX 3 4 5
* Nodes D G S
M1 3 2 5 5 MOD1
RG 4 2 343
RL 3 5 6E6
D1 5 3 DIODE1
.MODEL MOD1 NMOS VTO=1.109 RS=1.474 RD=1.59 IS=1E-15 KP=0.597
+CGSO=23.5P CGDO=4.5P CBD=53.5P PB=1 LAMBDA=267E-6
.MODEL DIODE1 D IS=1.254E-13 N=1.0207 RS=0.222
.ENDS

Can anyone help?

Best regards
Carsten Wind
Denmark

Hello Carsten,

4a)
Ctrl-right-mouse-click on the placed symbol nmos.
Change Prefix:MN to Prefix:X

2) I always recommend to save model files in the folder of the
schematic.

Best regards,
Helmut

Hello Helmut,
Thanx for your answer.
I did what you proposed in 4a) and it worked :-) But what does it do? What is Prefix and what does a change from MN to X do?

Then, how should the .include statement look like if the model files is placed in the folder of the schematic?

Best regards
Carsten Wind

Hello Carsten,

The X prefix tells the SPICE netlister that the device is represented by a subcircuit, and not an intrinsic model.

If the subcircuit is placed in the same directory as the schematic, then the include line is simply:
.inc subcircuitfilename.ext

Regards,
Tony

--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:

Autoscaling can't be switched off. You can workaround this
by using a plot settings file which you reload after each
simulation run or you could add an upper and a lower trace,
e,g. +10V and -10V.

That is true, and I have defined the space-bar to reload the settings, so it behaves similar to in the schematic editor. I have set the scales to make it easy to compare the voltages/currents in my converters.

However some transient simulations take 20-30 minutes to run, and when you reload the plot settings, it gets rid of the cursors. Plus every 5-10 seconds, the plot re-autoscales as more results are added to it. I am having a fighting battle. I have also considered using min/max, but I like the scales I've chosen with 55V on the left and 550A on the right, and I'm not sure I'd get them to match as nicely.

I really want to rant, and I'm sure I want to connect someone to the output of the power supply, but to be honest, I am so thankful for LT Spice that I can only manage "Thank you Mike" :)

Guys all this is first year circuit theory. We all know and come across series to paarllel convertions of reactive networks that introduce FDR effects where the real part of the immitance function varies with freq and these are LINEAR circuits. And as no real device is devoid of inductive/capacitive parasitics ,no matter how small, freq dependancy should not be a mistery.

Nonlinear effects were the reason I started this thread for modeling such things as ferrite cores. Manufactures rountinely supply spice parameters for these devices which involve freq dependant effects related to nonlinear loss mechanisms ( hysterisis etc ) .
George

_____

From: Hubert Hagadorn [mailto:huhaga@...]
To: LTspice@...
Sent: Thu, 15 Sep 2011 21:20:01 +0100
Subject: Re: [LTspice] Re: Freqeucny Dependent resistor






I believe it is impossible to have a physically realizable resistor that is frequency dependent and has no reactive component. A transmission line comes close in that its resistance is almost constant for a range of frequencies, but as you know at very low frequencies, neglecting any series resistive components, its reactance is largely capacitive.

Hubert

----- Original Message -----
From: Tony Casey
To: LTspice@...
Sent: Thursday, September 15, 2011 12:43 PM
Subject: [LTspice] Re: Freqeucny Dependent resistor

<snip>
--- In LTspice@..., Christian Thomas <ct.waveform@...> wrote:

Well, that's a question AG.

Might we not be looking at a naive question here? Ie. Can I please have a
resistor that changes with frequency but with none of those nasty reactive
elements? If that's the case then looking in the s-plane is not the answer
being sought.

In which case the answer needed is "No, you can't. Or at least you can't
have a full solution. (I think that must be right). But we do have some
useful reactive components that perform that function, and that's what
everyone else uses. C and L in LTSpice; and their s-plane behaviour is
built in."

CT

</snip>
Hello Christian,

I'm sure you ask the question tongue-in-cheek, because you surely must be aware of instances where the real part of an impedance changes with frequency without significant change in the reactance.

What about the resistance of straight length of wire? This increases due to the skin effect, whereby as the frequency rises more and more of the current travels closer to the outer (indeed for circular cross-section, the only) surface of the wire, so in effect reducing the cross-sectional area of the wire. In the limit, there is also a change in the inductance per unit length too, but it is not significant compared to the change in resistance.

And although not strictly a "component", there is the free space acoustic radiation resistance of a diaphragm, which also rises with frequency up to the frequency where the circumference is approximately equal to the wavelength. I will concede in this example that the reactive part of the impedance also changes at a fair rate of knots over the same frequency interval.

I'm sure you already knew all that. But it does illustrate why it is perfect legitimate to seek frequency-dependent resistance models.

Regards,
Tony

[Non-text portions of this message have been removed]








--------------------------------------------------------------

This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom
they are addressed. If you have received this email in error
please notify the system manager. Please note that any views or
opinions presented in this email are solely those of the author
and do not necessarily represent those of the company. Finally,
the recipient should check this email and any attachments for
the presence of viruses. The company accepts no liability for
any damage caused by any virus transmitted by this email.


Gill Research & Development Ltd is a limited company registered
in England and Wales. Registered number: 3154453.
Registered office: The George Business Centre, Christchurch
Road, New Milton. BH25 6QJ

In message <CANj54jyWx1_Dsz+T+61doGF8U1dZckc49KVUW+gkYSdzQGQJwQ@...>, dated Thu, 15 Sep 2011, Christian Thomas <ct.waveform@...> writes:

My starting question was whether radiation impedance actually held up as only real - his example of a possibility. John then slightly moved the goalposts in response by saying that they were by definition only real;

No I didn't: I said radiation *resistance*, not impedance, is real.

This is OT and I will not respond further.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.