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Audio signal reading using PIC8720

 
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csshah



Joined: 28 Feb 2005
Posts: 24

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Audio signal reading using PIC8720
PostPosted: Wed Mar 23, 2005 10:20 am     Reply with quote

Hello
Finally I found out how ADC works in PIC but now the porblem is I want to read audio signals and as told by somebody yesterday pic cant convert the portion of the signal below ground. So still is there anyway I can read signals and convert them to dB using PIC without using any other hardware like rectifier or level shifter...


thanks in advance
bluetooth



Joined: 08 Jan 2005
Posts: 74

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PostPosted: Wed Mar 23, 2005 11:16 am     Reply with quote

Put a divider that sets the a/d input at half-scale and ac couple the audio signal into that point.
newguy



Joined: 24 Jun 2004
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PostPosted: Wed Mar 23, 2005 11:18 am     Reply with quote

What you want to do is no simple task. It sounds like you want to create an SPL meter (sound pressure level). If this is what you want, it's not easy to create an accurate one.

You will need an rms-to-dc converter. The most popular are Analog Device products. Here is a link to the AD636:
http://www.analog.com/en/prod/0%2C2877%2CAD636%2C00.html

Here is "the bible" of rms-to-dc conversion, the AD application guide:
http://www.analog.com/en/content/0,2886,773%255F866%255F15010,00.html

It seems to me that years ago I found a link to a homemade quasi-SPL meter, but I can't find it now. Google "spl", "schematic", and any other terms you can think of, and you may find something acceptable if accuracy isn't important.
csshah



Joined: 28 Feb 2005
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PostPosted: Wed Mar 23, 2005 5:32 pm     Reply with quote

hi
thanks for help. actually i dont want to read the value of siganl precisely, i m intending to move a bar depending on audio signal. so i just want an approximate value to move the bar. so if u guys know any proportinal equation or any hint regarding this would be highly appreciated!!!

thanks
csshah



Joined: 28 Feb 2005
Posts: 24

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PostPosted: Wed Mar 23, 2005 5:32 pm     Reply with quote

hi
thanks for help. actually i dont want to read the value of siganl precisely, i m intending to move a bar depending on audio signal. so i just want an approximate value to move the bar. so if u guys know any proportinal equation or any hint regarding this would be highly appreciated!!!

thanks
bluetooth



Joined: 08 Jan 2005
Posts: 74

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PostPosted: Wed Mar 23, 2005 5:41 pm     Reply with quote

bluetooth wrote:
Put a divider that sets the a/d input at half-scale and ac couple the audio signal into that point.


Try this - it's just what you want.
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