Hello.

I am looking for a peak rectifier circuit to rectify low frequency audio signals..however it is a little trickier than just a PR circuit.

I want the circuit to work only when the signal is decreasing.

Meaning that a normal PR would (let's say) include a capacitor with a charge and discharge behavior..
I -on the other hand- would like a pr that does not work (is off) during discharge times..
so I can only peak rectify the rising parts of a singal.

Is it possible?

Hope somebody can help,

thanx in advance,

xmat.

 

Can you draw a waveform of what you want? I don't get it.

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Ron

 

Ok.

Here is a schematic with the signal I am trying to peak rectify..(Both blue and green consist the signal,
while blue is the part I want to rectify and green the part of the signal I don't want to peak-rectify..)

All I want is to rectify the info of the signal when it is rising, while having no rectification of the signal when the waveform is going downwards..See schematic.

Think of it as a "selective peak rectifier"..Rectifies only the "rising" parts of the signal.

Also, if this is achievable, can I do the opposite thing, i.e rectify only the falling parts of the signal keeping the rising parts unaltered.

Thanx for your help,

xmat.

Attached Images

untitled1.gif (41.4 KB, 742 views)

 

Am I correct that the red line represents the output waveform (my drawing in Paint is shaky)? I don't know how to do that.
Well, I guess a peak detector and sample and hold would do it.

Attached Images

poo.gif (41.6 KB, 736 views)

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As with many of these questions, perhaps you should tell us what you are trying to do?, it might be (and often is!) that there may be a simpler approach?.

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Perhaps a digital VU meter circuit, and you could adjust the "decay time" to suit the frequencies involved.

 

Well, it is not always that simple..I don't want to bore the hell out of people with a 2000 words' post..

Anyway, for your information, I am trying to "selectively" peak rectify (rising or falling) parts of this waveform to extract from it information about the rising time-of-change of the signal, or the falling time-of change of it.

Main reason for that: I want to extract from the signal the "basic" peak, (meaning I have to filter all others), leaving its rising and falling characteristics INTACT...Got it?
(The picture I send u is ONE signal..The main problem with a common peak rectifier is that it cannot output the main/larger peak without altering its rising/falling characteristics..That is rate of change, I guess)

Maybe a slew rate block would do the trick..What'd u say?

Thanx for your willingness to help,

xmat.

 

No. :?
You need to show a waveform of input and output. I'm assuming you know what you want, but you just don't know how to do it.

__________________
Ron

 

I have a bad case of deja vu here.
I remember some weeks ago there was a thread on a very similar topic, a peak detector that had to preserve some other information to allow the signal to be re-contituted afterwards (or something like that).
To tell the truth I did not understand the problem then, and I dont understand it now.

JimB

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Perhaps a diferentiator circuit, where the output is the rate of change of the input is what you need? The rising edge will give a positive output and the falling edge will give a negative output. The amplitude of the output will be proportional to the rate of change.

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Sorry, guys..Multiple posts due to a short loss of memory..(need vacations)..See the following thread to understand what I am trying to do.

http://www.electro-tech-online.com/v...ic.php?t=17464

xmat.

PS:Ron H, a usefull schematic with input and output graphics for you to disolve your curiosity.

 

That still doesn't explain what you want to do!.

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Detect occurence of (impulsive) peaks within a noisy background, by using rate of change of signal as the parameter for detection, of let's say musical beats (beat detection)..
The signal you see is ONE signal, and I have to find I way to make a circuit understand it is one and not more...by detecting the fastest peak and passing it through unaltered while filtering extra peaks..Now?

 

Simple! - use a low pass filter, it's a very common technique!.

But I suspect that isn't what you've been asking?, because it bears no resemblance to anything else you've asked!.

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Really???That simple???

I should inform you that such technique has a limited dynamic range, i.e it totally filters out weak signals; or if u "tune" the filter to "hear" those weak signals, u get wrong beat detection during high level ones (level variation also changes frequency content, which enhances the potential for false detection..)...

What makes u think I NOT am saying what I am trying to do?

xmat