% MT 02 2018/19
% Problem Set 2 Exercise 4

V0 = 12;
C = 1000.0e-6;
R = 1800;
f = 60;

Tf = 70e-3;
w = 2*pi*f;

t = 0:0.05e-3:Tf;
n = length(t);

state ='on';


for i = 1:n
    Vs(i) = V0 * sin(w*t(i));
    switch state
        case 'on'
           VR(i) = Vs(i);
           iR = Vs(i)/R;
           iC = w*C*V0*cos(w*t(i));
           sumI = iR + iC;
           if sumI <= 0
               state = 'off';
               tA = t(i);
           end
        case 'off'
            VR(i) = V0 * sin(w*tA) * exp(-(t(i)-tA)/R/C);
            if Vs(i) >= VR(i);
                state = 'on';
            end
    end
end

plot(t, Vs, ':', t, VR, 'k', 'linewidth', 1);
xlabel('Time (s)');
ylabel('Voltage (V)');