Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- LTspice
- Messages
Search
|
Re: Help! How do I do find maximum signal easily!
--- In LTspice@..., Macy <macy@...> wrote:
Are you talking about GNU Octave and are you working under windows or linux? If you are working under linux then you may be able to write a netlist for ngspice. You would then be able to run all your analysis commands together between control statements, e.g: .control all analysis statements here .endc More examples here: But then you would have to post on a ngspice forum. |
|
Re: arbitrary solar cell model
Dear Andy and Dear Fred
toggle quoted message
Show quoted text
Firstly, I really cannot explain my feelings when I see that you do your best for to solve my problem, I thank you very much. Couple of days ago, I was in vacation and I was thinking that the problem can be from Voc and Isc calculators and actually when I separate the Evoc and Eisc from the main circuit and just grounded them, the distortion disappeared but again it is not working for 2 cells in series while by making two cells in series the open circuit voltage should be doubled which is not happening (it was happening before I separate the calculators but with distortion) ! For making the things more clear, I draw the circuit in Paint ( so ashamed that cannot work with schematics and SPICE good). and corrected circuit But solving this issue is a real challenge for me ! maybe there is only a mistake on nodes ! while it works in parallel not in series ! Again I should say that I really appreciate your helps so far thank you thank you and thank you again. Kind regards Hamed --- In LTspice@..., "qrx3" <fredh@...> wrote:
|
|
Re: Strange behavior for simple RC circuit
No, it would not. The first thing LTspice does is find the initial operating point. Voltage sources are set to their DC values, and effectively LTspice "waits" until everything stabilizes, before proceeding. Remember that a DC voltage source is unchanging. Ever. It's as if your 6V battery was created with the Big Bang and has been sitting at exactly 6V ever since that time. In effect you got what you asked for. If you wanted the circuit to start at 0V you should have set your battery to that. There are a few ways to tell LTspice to behave differently. One is to set the voltage source to start at 0V and turn on at slightly after t=0. Another is to instruct LTspice to not find that initial operating point. Andy |
|
Re: Strange behavior for simple RC circuit
On Sat, 13 Jul 2013 23:01:59 -0400, Julio wrote:
I am looking at simple RC circuit with a time constant of 1 sec and a 6 VLook at the .tran card (it's on the schematic.) Right click it and look near the bottom of the dialog box to find "skip initial operating point solution" and check it so that this step will be skipped. Then re-run the solution. Jon |
|
Strange behavior for simple RC circuit
I am looking at simple RC circuit with a time constant of 1 sec and a 6 V
battery. Doing a transient analysis, at t=0 the capacitor is already fully charged at 6.0 volts! I don't recall giving initial conditions for the cap, so if I did not shouldn't the cap start In a fully discharged state? Sincerely, Julio |
|
Re: different resistance for .tran and .ac not working any more?
--- In LTspice@..., "haubmi1" <Michael.Haub@...> wrote:
Hello Michael, You have used resistance values of 1f. That's a very bad idea. Change it to 1u and the simulation will run with the normal solver. Lesson from today: never use femto-Ohms. .subckt simple-openloopgain1 in out params: reakt=100Gig L1 in out {reakt} Rser=0 C1 2 1 {reakt} Rpar=0 R1 in 2 100G AC 1u R2 out in 1u AC 100G V1 1 0 0 AC 1 .ends simple-openloopgain1 Best regards, Helmut |
|
Re: Help! How do I do find maximum signal easily!
hmmm...maybe I was too quick to dismiss this
IF I use three 'different' text files, one for each analysis type, then bounce between them! Now if there is just some way to include the the command strings: 'file' 'export' select style of output, overwrite, yes is there a way to add command strings like this?? If so, you have REALLY automated this for me! --- dwh@... wrote: From: David Hawkins <dwh@...> To: LTspice@... Cc: Macy <macy@...> Subject: Re: [LTspice] Re: Help! How do I do find maximum signal easily! Date: Fri, 12 Jul 2013 16:07:44 -0700 [snip] and the .ac using specific values requires storing on theWhy not put all the relevant text into file, and then .include it. It makes the schematic look nicer, and allows you to add header comments to the file along with relevant comments throughout the file. Cheers, Dave |
|
Re: arbitrary solar cell model
--- In LTspice@..., "analogspiceman" <analogspiceman@...> wrote:
There is no problem with LTspice. It is faithfully calculatingHuh? It's just the standard diode equation, as taught in every elementary device course. It may not be the best way to do what the OP is trying to do, but it seems quite reasonable to me to expect that it should give a reasonable answer. After all, spice solves this exact equation in maybe a majority of the active circuit it simulates, maybe for a dozen elements at a time, why should one expect that it can't handle it in a dependent source? To call this "extremely ill-formed" seems quite hyperbolic. These sorts of content-free, bullying responses make me think the bully is trying to avoid intelligent discussion by intimidation. Sorry I don't react well to that, and I really expect better from this forum. [/rant] The trouble arises from taking the ratio of two exponentialNot really, the exp() in the denominator is constant, and a reasonable value (e**21.7 is well in range of even single-precision floats), it just modifies the constant Visc multiplier to provide the correct open-circuit voltage. The case where things fail is when the input is negative so nothing should blow-up. The "very large" values occur with positive voltages where everything works fine. However you are certainly correct that LTspice seems to be launching itself off the end of its numerical range, ending up with a solution that is completely unrealistic yet the simulator does not recognize that this has happened. Look at the circuit when Vout is negative. The Bidiode source becomes a very low-value current source, with very low incremental conductance. It is in parallel with two high-conductance linear resistors. The Rs dominate what is happening in this regime, why on earth would spice feel the need to drive the voltage at that node so far negative that it wraps around? The circuit is very well-behaved in this range but somehow spice goes off the deep end. I'd have more sympathy if the sim failed at higher voltages when the B source had a significant dI/dV, not where the element is basically out of the circuit. Or if there were no resistors in the circuit so the dV/dI might blow up, but that's not the case either. As more proof that something odd is going on, why does this problem go away when the Voc voltage is changed from an expression of constant inputs to a pure constant? There is no reason the solver should be perturbing the constant inputs to that equation, but apparently it is. This also works fine in a transient analysis if one starts the independent sources at 0, but not otherwise. This raises the question: does LTspice try to solve things like this with some higher-level approach than an incremental analysis? Symbolic analysis? I'm at a loss. lead to numerical clipping, which LTspice handles well without crashingNice that it doesn't crash, but it is wrong to claim a valid solution when this happens, and worse that it uses this bizarre state as the starting point for the next iteration. At the very least make a mention of this in the error log. I'd prefer it recognize that the clipping (wrap-around, I think) has occurred and at least flag that it can not find a solution, as it does in many other situations, or try a different approach like it does for a difficult operating-point. As an experiment I converted the exponential current source into a logarithmic voltage source. Spice had even more trouble solving that at low voltages (not terribly surprised) but at least it recognized that it could not find a solution and moved on to the next point. Once it found a real solution it was fine from there on. but the clipped value causes the ill formed equation to have two solutionsI'd understand that if the equations had two solutions, stable or not, but they do not. What it reports is not a solution at all, KCL is not remotely satisfied at the reported "solution," there are a zillion Amps flowing out of that node from both the diode and the voltage source, and only 9 Amps flowing in. But somehow 73MAmps is within tolerance of 1.#INDA Amps, whatever that is. Latching onto the clipped solution can be avoided either by turningThe first option doesn't help the OP, but the second is a simple fix that seems to work well. I put the uramp() inside the exp() rather than outside and everyone's happy. Why this works when all it really does is add a discontinuity to the dI/dV is well beyond me. It is always best to use the built in devices whenever possibleI agree completely, and you'll see I still recommend that in my responses, but this bothers me anyway because I like to think of LTspice as a general-purpose nonlinear equation solver and here is a simple case of well-behaved equations yet it both fails misesrably and fails to recognize that it failed miserably (I have to think of the original Star Trek episode with "Nomad," once it realized it had made a mistake and, worse, failed to correct its mistake it had to self-destruct. I'm not advocating that behavior for LTspice). Cheers, sorry for the rambling, have a great weekend all, Fred |
|
Re: arbitrary solar cell model
Hi Hamed,
toggle quoted message
Show quoted text
I still recommend using the standard diode elements instead of writing your own, the only reason you would not be able to do that is if you need to change the Temperature -during- a transient simulation, e.g. I think everything else (irradiance/Isc) can be adjusted dynamically, and you can have multiple cells in any topology, all with different temperatures and Isc. Temperature can be swept for one/multiple/all devices in an Operating Point solution if that's what you need. If you still think this does not meet your needs please state what you have to do that you can't do with the standard model and I can show you how to fix your equations so that it works. Whether it's reasonable or not LTspice can not handle your equations as you have written them, but it can be fixed. -Fred --- In LTspice@..., "qrx3" <fredh@...> wrote:
|
|
Re: different resistance for .tran and .ac not working any more?
--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:
Hello Helmut, i have uploaded Files>Temp>loopgain-probe-test.zip. I don't know what was the exact problem as a similar spice desk at work did not run as expected. Here at home the loop-gain probe did run in the new spice desk i made, but only with the alternate solver. If you like you can have a look at it and tell me why it needs the alternate solver for DC bias point. I will check on Monday why it did not run correctly at work. Cheers, Michael |
|
Re: Help! How do I do find maximum signal easily!
[snip] and the .ac using specific values requires storing on theWhy not put all the relevant text into file, and then .include it. It makes the schematic look nicer, and allows you to add header comments to the file along with relevant comments throughout the file. Cheers, Dave |
|
Re: The road to LTspice
John Woodgate
In message <krpvc7+8b3g@...>, dated Fri, 12 Jul 2013, Helmut <helmutsennewald@...> writes:
The point isn't whether it's Fahrenheit or degree. It's about stealing knowhow.I know: I heard the story before, in a company seminar on NOT giving away know-how. Translating 830 degrees to the cooking oven scale was just another of my weak jokes. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk Why is the stapler always empty just when you want it? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
|
Re: The road to LTspice
Hello John,
toggle quoted message
Show quoted text
The point isn't whether it's Fahrenheit or degree. It's about stealing knowhow. Best regards, Helmut --- In LTspice@..., John Woodgate <jmw@...> wrote:
|
|
Re: The road to LTspice
John Woodgate
In message <krpsf9+e62p@...>, dated Fri, 12 Jul 2013, Helmut <helmutsennewald@...> writes:
And so I got on the phone and called down to Fab 3 over at Intel and I said what temperature are the ovens at and they said 830 degrees.I guess that's Fahrenheit - Gas mark 23 (not in Germany, which has bigger marks!). -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk Why is the stapler always empty just when you want it? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
|
Re: Help! How do I do find maximum signal easily!
still requires a LOT of fussing around.
bouncing between wide band .noise and 'regular' .ac analysis and the .ac using specific values requires storing on the schematic a list so long that it makes the schematic the size of a postage stamp in auto size. perhaps a plus sign on the first of a few lines will allow wordwrap - narrow width with long list. getting an output requires click file, export, then select real, imaginary ofrmat, and then YES overwrite existing *.txt file. Then run a script in octave to grab all the data, do the conversion to something meaningful and evaluate whether I did what I wanted to. But, other than all this mucking about, I CAN get my answers!! whew! it gets me there. --- Andrew.Ingraham@... wrote: From: Andy <Andrew.Ingraham@...> To: LTspice@... Subject: Re: [LTspice] Re: Help! How do I do find maximum signal easily! Date: Fri, 12 Jul 2013 12:35:43 -0400 I'm puzzled, because this seems like exactly what you were looking for. Isn't it? I don't think it could be much simpler. You can probably avoid the "dB" by setting up your AC plot with a linear Y axis. Andy |
|
Re: The road to LTspice
Hello Howard,
toggle quoted message
Show quoted text
I like especially this part of the story below. ... And she said well why don't you call Fab 3 over at Intel and ask them what the temperature is. And so I got on the phone and called down to Fab 3 over at Intel and I said what temperature are the ovens at and they said 830 degrees. And I said thank you. Best regards, Helmut --- In LTspice@..., Howard Hansen <hrhan@...> wrote:
|
|
Re: The road to LTspice
Thanks for posting the links. All were very interesting.
toggle quoted message
Show quoted text
Howard On 7/12/2013 2:51 PM, Helmut wrote:
|
|
Re: LTspice model for a 120V 4W LIGHT BULB in a Wien bridge oscillator ?
--- In LTspice@..., "ron.ck722" <ron.ck722@...> wrote:
Hello, Please stop this thread. Best regards, Helmut I will delete further messages. |
|
Re: LTspice model for a 120V 4W LIGHT BULB in a Wien bridge oscillator ?
For those interested in further simulations of low distortion Wein oscillators and Ultra-linear VCOs, here are 3 articles:
toggle quoted message
Show quoted text
1) Anne Watson Swager, "DOS-based analog-simulation software" EDN, May 21, 1992. 2) LTC's late Jim Williams' "Max Wein, Mr. Hewlett and a Rainy Sunday Afternoon" somewhere in the Linear Technology archives. Good references to Max Wein, Bill Hewlett and Jim, himself. 3) Jim Williams' "The Zoo Circuit - History, Mistakes and Some Monkeys Design a Circuit" on Jim and his good buddy, Bob Pease's obsession with Ultra-Linear V/F converters. Also somewhere in the LTC archives. My copies of 2) and 3) aren't dated. They may have been copied from one of several Analog design books Jim and Bob did together. Regards, Ron --- In LTspice@..., "xe3po" <xe3po@...> wrote:
|
to navigate to use esc to dismiss