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Re: ScanTesla program

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:

Original poster: "Jim Lux" <jimlux@xxxxxxxxxxxxx> 

Matlab wouldn't find closed form solutions.  You build the matrix up from
the component values, then solve it for the voltages and currents (which is
what SPICE does for the "steady state" AC solutions).  Nothing keeping you
from changing the matrix as a function of time.

In this case we are not interested in the sinusoidal steady state
solution. The input is a square wave, and the transient is important.
The simulator that I have implemented in the sstcd program uses
state equations, solved by numerical integration with a trapezoidal rule. It´s simple and efficient, for a fixed structure.

I, too, thought that.  But once you've got a half dozen or so components in
the circuit, it gets easier to write a simple routine to crank up the
admittance matrix (you write a "connect component between node x and node y"
routine, so your circuit design is just a series of calls to that routine).
Especially if you make the routine something like:
addcomponent (complex impedance, node 1, node 2)
and then do
Ymatrix = zeroes(20);        % makes a 20x20 matrix of zeros
addcomponent (resistance, a, b,Ymatrix)
or
addcomponent (1/(1j * omega * capacitance), a, b, Ymatrix)

It's possible to write a nodal system that solves for the time-domain solution at a small time interval ahead. A bit more complicated that sinusoidal steady-state analysis, and somewhat slower than state equations. But equally precise solutions are possible. If everything is linear, that solution can be very fast.

I would not consider using Matlab, Excel, or similar huge packages for this, quite simple, analysis, that has to be done fast. Everything that is needed is a routine to solve a real system of linear equations.

Antonio Carlos M. de Queiroz