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Peak Detector Circuit
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mauijan:
I am trying to design a peak detector circuit. But it needs to be a special kind of peak detector.
If a more positive peak arrives, of course the circuit needs to detect and hold it. But if a smaller, also positive peak comes, it needs to forget the last one and store this new, smaller peak. It basically needs to store every new max value. The signal is always positive.
The signal is a sinusoidal waveform with frequency of about 33 Hz. The frequency can also be lower but not higher. For every cycle the highest peak needs to be detected, even when the peaks are getting smaller in magnitude. I have attached an image that explains this behaviour...
Can anyone help?


pcprogrammer:
Hi mauijan, welcome to the forum.

For such a low frequency, I would use a microcontroller. You will have to bring the signal voltage in range of the ADC and write a bit of software.

On digital values it is easy to do this. Track the maximum, and hold it when the value drops below. Then track the minimum and when this is found start tracking a new maximum, and so on.

Doing it with electronics will require a fair bit of components I think. (Not really my field of expertise)
David Hess:
For a hardware only implementation, I would use two peak detectors and a differentiator.  The differentiator sets or resets a flip-flop to select which peak detector is providing the output, and which peak detector is monitoring the input and needs to be reset.

The differentiator output goes high or low depending on the slope of the input signal, which drives edge sensitive logic to control the flip-flop.  This is a noisy operation so careful filtering will be required.
MasterT:
For maximum value in each period combine peak detector with zero-cross reset circuits
pcprogrammer:

--- Quote from: MasterT on October 26, 2022, 06:33:05 pm ---For maximum value in each period combine peak detector with zero-cross reset circuits

--- End quote ---

For this to work the signal should cross zero where as the original post states:


--- Quote from: mauijan on October 26, 2022, 12:49:43 pm ---The signal is always positive.

--- End quote ---

The idea of David is interesting, but as I expected quite a bit of components to make it work.

Edit: For the software solution it is also needed to apply some filtering in the code, but that is not to difficult either.
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