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Re: Saving and restoring inductor current
Hello Vlad and Alexander (and Helmut, who is always such a gentleman expert), Thanks for noticing.? The things that interest me most about LTspice are always so arcane and often not of interest to most users so it is nice when some of the more sophisticated group members take notice (kind of like the situation with Adrian Immler and his amazing, improved tube models). I haven't tried it yet, but thought this "dual inductor" would be useful in a improved version of LTspice's example file transient domain loop-gain analyzer that uses .measurement statements because it could perhaps save a lot of time lost recalculating steady state at each new frequency step of the analysis. In his Ridley Works software (was Power 4-5-6), Ray Ridley uses a seemingly improved variation of the post processing loop-gain analyzer technique for switching circuits (his Excel engine generates a LTspice version of the subject schematic).? His software requires 32 bit Excel and all my machines are 64 bit, so I haven't been able to try his free, limited, but complete example (for buck converters only).? Thus I haven't been able to examine exactly what his software does to determine if it has improved upon the standard methods that are used in the LTspice example file. If you can, please try out his free software and report back what you think of it.? It also generates superb, elegant and efficient LTspice models for winding and core loss (something I have done on a case by case basis as needed, but his software has generalized automated method of doing so).? We could probably duplicate his methods. The transient domain loop-gain analyzer essentially performs a discrete Fourier transform at each analysis frequency point.? This can be problematic with much injected fractional cycle noise if the switching frequency and the test frequency do not both end on exactly whole periods.? The usual solution to this problem is to apply a complicated and computationally expensive tapered windowing function to minimize the deleterious effects of fractional alignment.? A smarter way around this problem might be to select the test frequency points and cycles used such that the test and switching frequencies are always related to each other by whole numbers ratios (for the parametric output plot, there is no need that frequency points be evenly spaced). My goal is to create a transient domain frequency response analyzer for switching power supplies in LTspice that produces as clean and noise-free results as does SIMPLIS while still running reasonably quickly. ---In LTspice@..., <imbvlad@...> wrote : Hello analogspiceman LTspice can save and restore node voltages, but not branch currents. This means that by using ".savebias time=<tstop>" and ".loadbias" a simulation with inductors is only partially saved and restored because inductor currents are ignored. It occurred to me that by making a "dual inductor" using current sources and a capacitor, one might trick LTspice into saving "inductor" currents. The inductor dual is very simple and can be a subcircuit with the inductor symbol edited to represent the dual inductor with the expected symbol. Don't how this compares speed-wise and coupled inductors would require an extension, but this technique might prove useful in certain stepped simulations that could run much quicker if the operating point did not need to be refound each time. That's a nice trick, thank you. The penalty shouldn't be that much if not too many inductors are used, for example a SMPS could really use that. Even filters that are not too large could benefit from this.? Coupled inductors might be trickier to set up, though. -- Vlad |
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Re: Using BV exp(), log() for numerical compression ,wrong result ?
¿ªÔÆÌåÓýI suppose you do realise that you can make one or both axes of a
plot logarithmic. You can also plot, for example log(V(out) on a
log axis, so get a log-log scale, using waveform arithmetic. Best wishes John Woodgate OOO-Own Opinions Only J M Woodgate and Associates Rayleigh, Essex UK On 2018-11-27 01:07,
ericsson.sunshine@... [LTspice] wrote:
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Re: Edge triggered b-source logic and integrated averaging in LTspice
Hello Vlad (and other group members), Earlier today I received a message from Mike.? There is a now a new update of LTspice available in which this minor bug has been squashed. ---In LTspice@..., <analogspiceman@...> wrote : Hello Vlad, I noticed that bug and reported it several days ago. Perhaps it would help if you reported it as well. It only is a problem for "B I=" sources that include a defined function and that specify both Rpar and Cpar. Either one alone is okay. |
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How To Add Potentiometer
"snopro.olmstead23" (Surpher) asked how to add a potentiometer in LTspice.? Your message hasn't shown up here yet.? I guess Yahoo's servers are still working on it.? Please no need to send the same question over and over. Potentiometers don't come with LTspice.? Nor with SPICE. Consider whether you really really need one.? Electrically, a potentiometer is just two resistors in series.? Two reasons why you might want one anyway are:? (1) You want your schematic to look pretty; or:? (2) You want to .STEP your simulation through a range of settings.? Otherwise, I can't think of a reason for needing one, but there might be one.? If your circuit has a potentiometer and you don't need to do either (1) or (2), then just calculate the two resistor values, and you're all set!? Much simpler. However, don't give up yet.? There are a number of potentiometer symbols/models that have been uploaded to this group's Files section.? Choose one, then stick with that one.? Start here: ? ? Files > Lib > Potentiometer ? ?? or here: ? ? Files > Tut > Potentiometer ? ?? and there are others too.? As I say, pick one and go with that one. Your next step depends on which one you downloaded and plan to use.? This might help: If you put the symbol file (*.asy) in the same folder with your schematic, then do this: ? (a) Open the schematic. ? (b) Go to Add Component. ? (c) At the top of the pop-up, there is a "Top Directory" with two choices: LTspice's library, and the current directory.? Change it to the current directory. ? (d) Now the potentiometer symbol is a choice and can be added to the schematic. Whether you need to add a .lib file reference, that depends on the potentiometer you've chosen.? If you need to add a .lib file yourself, add the following to your schematic (as a SPICE Directive): ? ? .inc filename.ext where filename.ext is the actual filename of the .lib file -- so it might be something like "potentiometer_standard.lib" or "potentiometer.sub". The next thing is to right-click on the attributes next to the potentiometer symbol, to set its value and the amount of rotation you want.? Hopefully that's obvious, because it depends on which one you've chosen. If you have already downloaded one of the potentiometer symbols and can't get it to work, then please provide more information.? Tell us exactly which one of the potentiometer models you chose.? Preferably, you should ZIP your schematic AND the potentiometer symbol file AND its model file, into one .ZIP file (that's .ZIP not .RAR or other!), and upload it to the group's "Temp" folder so we can see what you've done so far.? Then write another message saying that you did that. Regards, Andy |
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Re: Saving and restoring inductor current
Hello analogspiceman
LTspice can save and restore node voltages, but not branch currents. ThisThat's a nice trick, thank you. The penalty shouldn't be that much if not too many inductors are used, for example a SMPS could really use that. Even filters that are not too large could benefit from this. Coupled inductors might be trickier to set up, though. -- Vlad ______________________ ltspicegoodies.ltwiki.org -- holding, among others: a universal analog/digital filter, block-level models for power electronics (and not only), math blocks with a more stream-lined approach, some digital ADC, DAC, (synchronous-)counter, JKflop, etc. |
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Re: 74hc_v.lib file
Eric asked about the file "74hc_v.lib", needed in a downloaded simulation. I don't know if you found the answer to your question already (the replies I received might not be in order).? However, the file you were looking for is in the group's Files, here: ? ? Files > Lib > Digital 74HCxxx > 74HC_v.lib ? ? I remind people to try the "Table of Contents" file (all_files.htm) when something like this is needed. By the way -- the schematic uses the 74HC194 but not the original/bipolar 74194, despite the name of the schematic.? I guess that schematic was an answer to someone's question and you'd have to go back to that question (99370) if you wanted to see why the names didn't agree. Regards, Andy |
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Re: Saving and restoring inductor current
Hello analogspiceman. ? Thank you for enlightening me. I added the following to my collection of models: ? .subckt Lrememb 1 2? .param ? L=1 Rser=1m Rpar=1/Gmin ic=0 C1 3 0 {L} Rser={1/Rpar} Rpar={1/Rser} ic={ic} G1 1 2 3 0 1 G2 3 0 2 1 1 .ends Lrememb ? Bordodynov. 27.11.2018, 04:52, "analogspiceman@... [LTspice]" <ltspice@...>:
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Re: 74hc_v.lib file
Hi Eric. I opened your circuit and everything was modeled. I just did: .tran 0 10m 0 uic I have installed libraries in ../Documenty/LTspiceXVII/ .. You can find it on my page: ? Bordodynov 27.11.2018, 04:51, "eohenares@... [LTspice]" :
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Re: 74hc_v.lib file
Hi Helmut, I'm sorry I found the 74hc595 in the files which will also do and has both the .asy and .lib files. Pls no need to send the .lib of the 74194. Thanks and best regards, Eric
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74hc_v.lib file
Hi Helmut, Do you happen to have still the "74hc_v.lib file" used in the "74194 test.asc" schematic? It is not inside the zip file so I could not load it into the "sub" directory. The schematic would not run and is looking for it. I tried working through your instruction how to convert a .asc file into .lib but was too heavy for me. I reloaded the file dated Nov 19, 2016 for reference. I wrote an ealier email but seems did not go thru. Thanks and best regards, Eric ? ? ? ? ? ? ? ? ? ? ? ? |
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74hc_v.lib file
Hi Helmut, Do you happen to have the "74hc_v.lib" file that is in the "74194 test.asc" schematic? I reloaded the file of? Nov 19, 2016 for reference. The actual .lib file is not in the zip that I could load to my "sub" directory. So it would not run I tried working through your instruction to convert a .asc to a .lib file but just too heavy for me.? Thanks and best regards, Eric |
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Saving and restoring inductor current
LTspice can save and restore node voltages, but not branch currents.? This means that by using ".savebias time=<tstop>" and ".loadbias" a simulation with inductors is only partially saved and restored because inductor currents are ignored.? It occurred to me that by making a "dual inductor" using current sources and a capacitor, one might trick LTspice into saving "inductor" currents.? The inductor dual is very simple and can be a subcircuit with the inductor symbol edited to represent the dual inductor with the expected symbol. .subckt L 1 2 .param L=1 Rser=1m Rpar=1/Gmin C1 3 0 {L} Rser={1/Rpar} Rpar={1/Rser} G1 1 2 3 0 1 G2 3 0 2 1 1 .ends L This seems to work well and each run picks up where the previous run left off.? Here is a test simulation. V1 1 0 1 AC 1 Don't how this compares speed-wise and coupled inductors would require an extension, but this technique might prove useful in certain stepped simulations that could run much quicker if the operating point did not need to be refound each time. |
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Re: Using BV exp(), log() for numerical compression ,wrong result ?
Hi, Andy:
Before your explanation, I didn't notice "complex logarithm" is a special case, maybe not supposed to be supported by any SPICE. About the compression application, I didn't really have the complete idea, maybe it would be like the,.... For example, when someone reading a book, the edge on every page often empty, and be used to sketch some thing on, some graphs/pictures to decorate the layout of the page. They often are not the primary parts. To analogy, if there are some main data, which typically are numerical values, and has its general scale on the range of greater than 0.01, though its format could support to very least 1e^-16, or some, such that, maybe I could merge those loged numbers secretly into the "main data", and leak .... to somewhere who concern it, without interference others who typically don't care those smaller values which is under 0.01. Just some ignorant ideas. I didn't implement it yet. Best regards. ---In LTspice@..., <ai.egrps@...> wrote : ericsson.sunshine wrote: ? ? "LTspice couldn't treat the negative value of nature log very well, which normally return the complex value ..." ? ? "LTspice couldn't see the complex (imaginary) parts. And treat it very well, as it should be treated in the normal math world." I think most people here understand this: "The natural logarithm function ln(x) is defined only for x>0.? So the natural logarithm of a negative number is undefined."? Undefined means it has no defined value when x is negative, or zero.? I think in math, this would be represented by NaN (but I might be wrong). The "complex logarithm" is an extension to complex numbers, but it differs from an ordinary logarithm.? Perhaps you work in a math world that treats the complex logarithm as a normal logarithm function, but I think most of us engineers do not.? The logarithm functions in LTspice are not defined to be complex logarithms, therefore one should not expect them to behave as complex logarithms; they are the ordinary variety of logarithm functions, which are undefined for negative arguments.? The exponential function exp() is not the inverse of the complex logarithm function. Maybe it would help to understand what you are trying to accomplish.? I understand that you may be interested in compressing a wide dynamic range into a smaller one; but is this for signal processing?? Waveform visualization?? Theoretical analysis of non-physical signals or entities?? (Not that I'm asking for my own sake.? But it helps to know where one is going, before making the first steps, and finding that one has stepped into a hole.) Regards, Andy |
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Adding Potentiometer
Hey guys I¡¯m totally new to LTspice. I¡¯m using it to build guitar tube amps. One thing I need is to add a potentiometer. I tried following the help text file but could not get the potentiometer to actually work. I amable to use the symbol but that is as far as I¡¯ve gotten. I don¡¯t know how to install the .lib file to get it to work. I¡¯m sure this is very easy for everyone here but not for me as I am completely new to the program. If someone could provide a step by step instruction on how exactly to go about adding a potentiometer to LTspice I would greatly appreciate it. Thanks!
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Adding A Potentiometer
Hey guys I'm totally new to LTspice. I'm using it to build guitar tube amps. One thing I need is to add a potentiometer. I tried following the help text file but could not get the potentiometer to actually work. I am able to use the symbol but that is as far as I've gotten. I'm sure this is very easy for everyone here but not for me as I am completely new to this program. If someone could provide a step by step instruction on how exactly to go about adding a potentiometer to LTspice I would greatly appreciate it. Thanks! |
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How To Add Potentiometer
Hey guys, I'm totally new to LTspice. I'm using it for building guitar tube amps. I really need to add a potentiometer to LTspice. I'm sure it is probably simple to everyone here but not to me. I read the help text file and I'm not able to get the potentiometer to actually work. If someone can please help with this I would greatly appreciate it. I would like a step by step guide on how exactly I go about adding a potentiometer. As far as I could get is being able to use the symbol. But I can't figure out how to add the .lib file and have the potentiometer actually work. Again, if I could get a step by step explanation on how exactly to add a working potentiometer that would be awesome. Sorry if I sound like such a newbie, because I am. thanks! |
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Re: LTspice model for capacitor start single phase motor
¿ªÔÆÌåÓýTry these links: ? ? ? ? ? ? ? ? From: LTspice@... [mailto:LTspice@...]
Sent: Thursday, November 22, 2018 6:17 PM To: LTspice@... Subject: [LTspice] Re: LTspice model for capacitor start single phase motor ? ? just trying to study how to proper run/ start a single phase motor with a inverter, I already have the inverter model , but seems have problem with the motor model with speed/torque. ? I can find a two phase motor and three phase examples. but nut sure how to build a single phase one. ? any example of single phase motor would be very helpful ? thanks!! |
John Woodgate