ltspicesimulation
I'm trying to automate LTSpice using the command line. I have tried the following command several times:
test.asc -run -b
However, it only opens my schematic in LTSpice and does not run it! I have no idea whats wrong with it. The schematic is a very simple circuit which should be run in less than a second. Does any one have idea? How should I resolve this issue?
Thanks
Running a simulation multiple times and changing multiple component values is a bit more involved than just changing one (which is not so bad)
Here is the concept for changing one value:
.param X=R .step param X 100 500 50 to step the value between 100 and 500 in increments of 50.Example:
Result:
For multiple values, the only way I found to work was using a list of values for X, and using the table statement. This is probably best explained with an example (reading the help for the commands used will probably be helpful here). But note that the table command syntax is in the form table(index, x1, y1, x2, y2, .... xn, yn), takes index as input and returns an interpolated value for x=index based on the supplied x,y pairs.
In one of my simulations I needed to perform 12 simulations whilst changing 3 different component values, here are the commands:
.step param X list 1 2 3 4 5 6 7 8 9 10 11 12
.param Rin1 = table(X, 1, 1,1p, 2, 1p, 3, 1p, 4, 4478, 5, 4080, 6, 3400, 7, 2200, 8, 1p, 9, 1p, 10, 1p, 11, 1p, 12, 1p)
.param Rin2 = table(X, 1, 4997, 2, 4997, 3, 4997, 4, 499, 5, 897, 6, 1577, 7, 2777, 8, 4997, 9, 4997, 10, 4997, 11, 4997, 12, 4997)
.param Tval = table(X, 1, 56, 2, 56, 3, 27, 4, 1G, 5, 1G, 6, 1G, 7, 1G, 8, 1G, 9, 330, 10, 330, 11, 120, 12, 120)
.param Kval = table(X, 1, 316, 2, 147, 3, 147, 4, 6340, 5, 6340, 6, 6340, 7, 6340, 8, 6340, 9, 6340, 10, 825, 11, 825, 12, 316)
Result:
Hopefully you get the idea, you could maybe produce a script that would produce the necessary SPICE commands when you fill in your desired values. Or just create a template (e.g. I just copied and pasted the above into a few different simulations and changed the values)
If the above doesn't do what you want, then maybe look at something like NI's multisim (I think it has some batch simulation options, although I'm not sure how useful they are) It may also be helpful to ask on the LTSPice forum and see if someone knows of a better way of doing things.
I think you should be displaying the differential voltage across V1 since it isn't ground referenced. The output (which is ground referenced) is behaving as expected. I don't think that waveform you are seeing makes sense though..
BTW, there is a (possibly hidden) place to add series resistance in V1. Make sure that "Parasitic Properties" Series Resistance is set to 0, and I would suggest checking off "Make this information visible".
Edit: This simulation behaves similarly when I simulate it, and it's due to the bottom end of the source floating around. If you connect a 100K resistor from the bottom end of the source to ground it does not affect the output voltage but the top of the source looks more like what I think you would expect:
Best Answer
The command "test.asc -run -b" does not run LTSpice, it simply opens the file "test.asc". It only opens in LTSpice because the file association for ".asc" is assigned to LTSpice in the operating system (if it was assigned to eg. notepad then it would open in that program instead). The ".asc" filetype is set up to only pass the file name to LTSpice, not the whole command line.
Your command should start with the name of the executable you want to run ie. "scad3.exe", followed by any parameters you want to give it ie. "test.asc -run -b". LTSpice will then be able to read the full command line, run the simulation and produce the expected output files ("test.log", "test.net").