MATLAB: Use of monostable rising and reset block together

monostable fallingmonostable risingresetreset blocksimulink

Hello,

I use a monostable falling bloc that holds the output value to TRUE when it detects a falling edge from one to 0.

It holds this value for a specified time of 1000seconds

Let’s say it detects a falling edge at 100s It holds the value true from 100 to 1000 seconds.

* But I also want when needed to be able to reset the bloc « monostable falling »** : it means that it will re-evaluate/detect if there is a falling edge. For example the output value of the bloc is true from 100 to 1000s but at 600 s it becomes false again (because of the RESET) and the bloc starts RE detecting if there is a falling edge

Thank you for your help ! 🙂

Best Answer

Hi,

From my understanding you are trying to reset the monostable rising block to False/0 whenever an external trigger is provided.

To solve your question, there is subsystem in Simulink named Resettable Subsystem in which you could place your monostable block and configure the reset block as per your requirement.

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MATLAB: Count rising edge in wave

If I understand correctly what you want to do, this seems to work (requires the Signal Processing Toolbox for findpeaks):

D = load('sigX');
x = D.req_read(:,1);
y = D.req_read(:,2);
dy = gradient(y, mean(diff(x)));                % Take Derivative
[dypks,ix] = findpeaks(dy, 'MinPeakDistance',20, 'MinPeakHeight',1E+7);
figure(1)
plot(x, y)
hold on
plot(x, dy*1E-9)
plot(x(ix), dypks*1E-9, '^g', 'MarkerFaceColor','g')
hold off
grid
axis([0  1E-7    ylim])

It is fairly straightforward. It uses the gradient function to take the derivative of the signal, then uses the Signal Processing Toolbox findpeaks function to find the peaks in the derivative, corresponding to the rising edges of the signal. I included in the findpeaks call threshold values for the magnitude of the peaks to include (in 'MinPeakHeight') and the distance between then (in 'MinPeakDistance').

The findpeaks function returns the value (height) of the peaks in ‘dypks’ and their index locations in ix that you can then use to locate the peaks with respect to ‘x’. The plot calls illustrate this usage. The scaling factor of 1E-9 scales the derivative plot to the original signal so that I could overplot the derivative and the signal to verify that the derivatives did what I wanted them to. Also, the axis call shows a part of the signal in detail. Comment it out to see the entire signal.

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It's because of the Unit Delay block "delaying" the output by 1 trigger.

If you move the Unit Delay block to the lower branch of the loop in the Triggered Subsystem (i.e., after the Output port), you get the counter firing on the first rising edge, as you originally expected.

- Sebastian

Best Answer

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MATLAB: Count rising edge in wave

MATLAB: Is a triggered subsystem activated on the second rising edge

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