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#### Understanding real time audio spectrum circuit

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#### Understanding real time audio spectrum circuit

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 Post subject: Understanding real time audio spectrum circuit  Posted: Fri Jul 13, 2012 8:56 pm

Joined: Sun Jun 03, 2012 9:27 pm
Posts: 6
Hy all, i want cu understand how the circuit works, and i want to understand the role of all components.
the diagram is that posted in this site:
http://www.waitingforfriday.com/index.p ... alyser.png
I don t don t know what :R1,R2 do?
the low power amplifier is working in open loop? i don t see the negative reaction
R5 and C1 is a low pass filter?
How you calculate them?

 Post subject: Re: Understanding real time audio spectrum circuit  Posted: Sun Jul 15, 2012 11:38 am

Joined: Thu Apr 01, 2010 6:23 am
Posts: 954
R1 and R2 mix the left and right audio channels. For the details on the LM386-1 just grab the data-sheet (the layout is part of the reference designs from the data-sheet). R5 and C1 are part of the audio design, the 10K resistor drops the input intensity (so the amp doesn't distort) and C1 helps to smooth the audio input.

To calculate RC filters just google, there are many on-line calculators available.

/Simon

 Post subject: Re: Understanding real time audio spectrum circuit  Posted: Sun Jul 22, 2012 12:50 pm

Joined: Sun Jun 03, 2012 9:27 pm
Posts: 6
Hy all, i have another question about the circuit

If i remove the resistor R2= 10k, the circuit will work properly???
and W5, W6 what they d0???

The frequency of the ADC is set to 20kHz, may i increase this frequency???

 Post subject: Re: Understanding real time audio spectrum circuit  Posted: Sun Jul 22, 2012 7:17 pm

Joined: Thu Apr 01, 2010 6:23 am
Posts: 954
You should leave the resistors as they are - they set the levels correctly.

All the points labelled 'W' are test points. Look at the project article for details.

Don't change the ADC rate unless you first understand how the code works... you will need to alter the code if you change the ADC sampling speed.

 Post subject: Re: Understanding real time audio spectrum circuit  Posted: Sun Jul 22, 2012 8:20 pm

Joined: Sun Jun 03, 2012 9:27 pm
Posts: 6
Hy all, Hy Simon
i sorry, but i suppose that the code is good?
because, i take the code that is on this site
i compile with MPLAB IDE v8.83, no errors
but if i take the hex, and i put it in the pic
the display is show me the spectrum, even i don't
put input signal

what does this mean???
something wrong on this code????

 Post subject: Re: Understanding real time audio spectrum circuit  Posted: Mon Jul 23, 2012 10:12 am

Joined: Thu Apr 01, 2010 6:23 am
Posts: 954
The original hex is available here on the forum, you can simply search for it if you want to compare.

If you are using the unaltered source-code then it is (most likely) that your circuit is not constructed correctly.

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