# CAD/Simulation software to determine capacitanceMarch 10, 2011 10:39 AM   Subscribe

I'm looking for a free (or trial) CAD/simulation software package that can be used to derive the electrical capacitance of geometric shapes in relation to one another.

Does anyone know of anything that is out there? There seems to be a lot of these for the semiconductor and MEMs fields (for \$\$\$). I'm interested in, for instance, a conductive sphere and a plane (where the sphere is charged and the plane represents ground) and seeing how the capacitance of this model changes with distance. Or other simplified geometries that give some estimating of capacitance without me having to get too much into the electromagnetics theory myself.

My interests in this is to analyze the energy storage potential to determine the possible energy levels from a static electric discharge. Thank you for your help.
posted by nickerbocker to Science & Nature (2 answers total) 1 user marked this as a favorite

I have used FlexPDE: http://www.pdesolutions.com/ in an electrostatics class to determine capacitances of different structures. There is a trial/student version that is free. It takes some knowledge of PDE's, boundary conditions as well as its scripting language. It comes with examples and I will also post this example code for you to play around with:

TITLE 'Capacitance Example'
COORDINATES cartesian2
VARIABLES
V { electrostatic potential }
DEFINITIONS
eps0=8.854e-12

EQUATIONS

BOUNDARIES
REGION 1 "Box"
START 'Outer' (0,0) Value(V)=0
LINE TO(.3,0) Value(V)=0
LINE TO(.3,.3) Value(V)=0
LINE TO(0,.3) Value (V)=0
LINE TO CLOSE

START 'Inner' (.1,.1) Value(V)=1
LINE TO(.2,.1) VALUE(V)=1
LINE TO(.2,.2) VALUE(V)=1
LINE TO(.1,.2) VALUE(V)=1
LINE TO CLOSE

PLOTS
CONTOUR(V)

SUMMARY
report sintegral( normal[ eps0 * grad( v)], 'Inner', 'Outer') / 1 as 'Capacitance (f/m)'
posted by mungaman at 1:14 PM on March 10, 2011

Thanks!!! I'll play around with it.
posted by nickerbocker at 2:54 PM on March 10, 2011

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