Nelma is a (command line) tool for numerically calculating various electrical properties of printed circuit boards or similar objects composed of conductors and dielectrics (however code is optimized for circuit board-like geometry).
It is currently capable of calculating capacitances between objects - nets on a PCB. It returns a spice-compatible description of an equivalent circuit of stray capacitances that can be for example used for more accurate circuit simulation. Alternatively it can also produce field data that can be plotted for example with Gnuplot.
Support for calculating resistances existed for a while but was later removed because it didn't receive much testing.
Nelma is available under the GNU General Public License version 2.
You will need:
The capacitances are calculated by:
The algorithm is therefore of O(n2) time complexity regarding the number of nets. This way we also get to calculate each capacitance twice. The difference between these two calculations is used as an estimation of numerical error.
The finite difference method allocates memory that is proportional the cube of dimensions. The field solving algorithm itself is of O(n3) time complexity.
The system of linear equations that is produced by the finite difference method is currently solved with a SOR iterative algorithm with a constant extrapolation factor.
This is a result of my term project. I have a paper (in Slovene) that explains in detail methods used by the program to calculate the capacitances and methods I used to verify the results. Send me a mail if you want to read it.
You can get source code of stable releases from the following location:
Nelma is also available from NetBSD's pkgsrc collection:
Keep in mind that this is a work in progress. Read the README file for installation instructions and a list of known problems.
Any Feedback is welcome.
Most likely there's an error in your configuration file. Run with "-v 256" option to turn up verbosity. Look for any error messages before the crash
It's also possible that you don't have enough RAM.
Do you have a material with 0.0 permittivity defined in your config file?
There's a Nelma export HID for PCB. You can currently get a patch from the SourceForge tracker.
In the patched PCB select File - Export layout - Nelma.
Please send bug reports or anything else related to Nelma to the author's email address firstname.lastname@example.org