Cross

[m-a-r-i-n]

I need help to solve this problem, i need create circuit to detect cross 2 sine wave voltage. Any sugestion is welcome!

View attachment 40291

 

[AN920]

Will the phase shift always be the same or variable?

 

[m-a-r-i-n]

Phase is variable,amplitude is constant. Circuit need detect cross two sine wave and
show that value of voltage.

 

[AN920]

Are the waves separate like on 2 inputs or combined at some point?

 

[saiello]

Couldn't you use a comparator that takes both inputs. When the output is zero, the signals are at the same voltage, i.e. 'crossed', then all you have to do is to take a reading from one of the inputs for the actual value.

 

[m-a-r-i-n]

Tanks to sugestion...there is final circuit:

View attachment 40312

 

[aniruddha]

Hi m-a-r-i-n,
I agree with zeppelin, why so complicated. ???
As far as the working is concerned, in the top line, 1st comparator is used to detect the crossing, the schmitt is to eliminate noise-chatter, 2nd comparator acts as a plain inverter to nagate the effect of "inverting scmitt trigger", and the 3rd comparator is just a vtg. follower acting as a buffer. Atleast thats what i've analysed

But the whats the purpose of that 4th comparator sitting at the bottom???
I think its quite unnecessary and makes the circuit complicated.
But surely u must have had some reason to use it. Care2justify? :-\

 

[AN920]

Looks possible to do with only 1 comp and 1 opamp

View attachment 40328

 

[m-a-r-i-n]

Well this is how i create the circuit in blocks....comparator compare two sin wave voltage, when output is 0, the comparator activate digital circuit to activate pump capacitor on the level of voltage from one voltage
sources. Then the output is equal cross voltage....this is short explanation

View attachment 40332

 

[m-a-r-i-n]

The basic circuit is sample and hold circuits,the simple sample and hold circuit is this:

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