ADC Sound detection

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PaioX

New Member
Hello,
I need some help with ADC and sound detection, I would like to detect voice over a telephone using it's speaker, I've tried to connect it directly (with 4 diode) to the ADC pin of a 08M but it seems that readadc gives random values...I think that I need some kind of amp circuit before ADC pin, isn't it?!
Can you give me a diagram using some op-amp like LM358?!
Thanks

Paride
 
D

Dippy

Moderator
Oh, Mr Search Engine got there first :)
I'm gld he did as I couldn't remember where that particular circuit was!


LM358 perhaps?

Does this help?
http://www.picaxeforum.co.uk/showthread.php?t=10778&highlight=sound+switch

There have been quite a few sound operated switch projects on the Forum. Spend a few minutes hunting around using 'Search'.

Page 10 onwards of the LM358 Data Sheet gives many circuits that can be modified if you are experienced with electronics. A few small changes are usually needed to go from dual rail to single rail designs. A few more changes are required depending on the microphone type.
And there are quite a few specific microphone chip amps on the market. All you need is to give the signal some gain , rectify and check o/p level to do your switching.
Data Sheet:
http://www.farnell.com/datasheets/36631.pdf

Note for future reference:
There are zillions of op-amps and many people (and no doubt designers on the internet) have a My Favourite Op-Amp. If you go to places like Farnell and download the Data Sheets from a dozen different Op-Amps you can build up a useful LIBRARY of example circuits. It's well worth 20 minutes doing this and may save a lot of time in future.

Enjoy.

Oh (after re-read) P.S. Are you talking about using a microphone or direct wiring to speaker?
 
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