Help with this dc offset circuit

Thread Starter

Mulo2k2

Joined May 20, 2021
7
Qualcuno può aiutarmi con una spiegazione della funzione di questo circuito.

Translated;
Can anyone help me with an explanation of the function of this circuit

I can't find any article on the web
 

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ericgibbs

Joined Jan 29, 2010
12,901
hi M,
The audio output of the OPA is connected via 10uF DC blocking capacitor and connected to the Analog input of an Arduino.
The two 100k's bias the ADC input to Vcc/2, so the AC audio signal can be converted by the ADC.

E

Update:

Added a simple diagram
 

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ericgibbs

Joined Jan 29, 2010
12,901
hi,
OK,
Do you know what the A0 pin is designed to do internally in the Arduino when programmed to be an Analog input pin.?
E
 

ericgibbs

Joined Jan 29, 2010
12,901
hi,
From that short clip of the Sketch it appears that the program is designed to measure the frequency of the Audio input signal.

It is possible that the OPA is being used to boost the level of the signal.?
If so the OPA could be set so that that output voltage is about +/-2.5V

As you my know the input pin of an Arduino should be limited to 0V thru +5v

Can you post all of the Sketch code.?

E
 

djsfantasi

Joined Apr 11, 2010
7,689
It is possible that the OPA is being used to boost the level of the signal.?
If so the OPA could be set so that that output voltage is about +/-2.5V

As you my know the input pin of an Arduino should be limited to 0V thru +5v
Why +/-2.5V on the OPA output?

Why not 0 - +5V...?

Makes things easier, doesn’t it?
 

ericgibbs

Joined Jan 29, 2010
12,901
hi dj,
I believe the original question is: what is is the function of the 10uF and the two 100k's

I have made it +/-2.5v before the 10uF, so that he can figure out the resultant signal at theA0 input.
E
 

ericgibbs

Joined Jan 29, 2010
12,901
hi Mulo,
Thats good to hear. Congratulazioni

I did two more simulations for you in case you had a problem
One without the 10uF and the other without the 100k's.
You can see the problem.!
The ADC input swings +/- 2.5Volts
E
 

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