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runLTspice demo

%% Demonstration of the runLTspice function
% Demo video at http://youtu.be/ax9H4eKuZv4
% Download runLTspice from:
%         https://dadorran.wordpress.com/2014/10/29/runltspice-m/
% Download this code from https://dadorran.wordpress.com
% LTspice schematic available from:
%       https://www.dropbox.com/s/y7j1vmyscvppsn4/RC.asc?dl=0

%% read the voltage and currents from the circuit
result = runLTspice('C:\Temp\RC.asc', 'V(n002)');

plot(result.time_vec, result.data{1})

%% apply a step input and plot the capacitor current and voltage wavforms
fs = 200;
step = [zeros(1, fs/2) ones(1, fs/2)];

res = runLTspice('C:\Temp\RC.asc', 'V(n002), I(C1)' , 'V1', step, fs);

plot(res.time_vec, res.data{1})
hold on
plot(res.time_vec, res.data{2}*1000,'r')
hold off
legend([ res.data_name{1} ' (v)'],  [res.data_name{2} ' (mA)'])

%% apply a noisy square wave and compare the supply voltage with capacitor voltage
sq_wav = [step step step step];
high_f_noise = filter(1, [1 0.9], randn(1, length(sq_wav))*0.1);
ns_sq_wav = sq_wav + high_f_noise;

r = runLTspice('C:\Temp\RC.asc', 'V(n001), V(n002)' , 'V1', ns_sq_wav, fs);

plot(r.time_vec, r.data{1})
hold on
plot(r.time_vec, r.data{2},'r')
legend('supply voltage','smoothed voltage')
hold off

  1. ilCapitano
    June 17, 2015 at 5:32 pm

    That’s a great function to control LTspice using Matlab.
    Is there a way to change the value of a resistor like u did with ‘V1’ ??


    • June 17, 2015 at 7:35 pm

      I’m pretty sure its possible. The runLTspice function basically just updates the .asc file which is a plain text file describing the schematic. You’ll see my code looks through the text file for “SYMBOL voltage” and then updates any voltages for which a change has been requested. You should be able to do something similar for “SYMBOL res”.

      Good luck!

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