Author Topic: Properties of a microphone  (Read 4194 times)

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Offline malexTopic starter

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Properties of a microphone
« on: January 19, 2009, 03:16:24 PM »
While I was looking around electronic stores I found this microphone that was less than a dollar or so but its basically a little cylinder with two wires.

How does this device work?  When it receives sound does it alter the resistance and I can take a reading via a voltage divider?

Also, is the resistance dependant on the frequency it receives or the intensity or a bit of both?  I don't really have more details but I can try to answer if theres some clarification.  Also, if it works in a completely different way, tell me.

Thank you.

Offline householdutensils

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Re: Properties of a microphone
« Reply #1 on: January 19, 2009, 03:35:49 PM »
As far as I know there is a filament inside called a diaphragm. Any sounds vibrate the diaphragm which modulates the current passing through it.

As for whether you can read any resistance change via voltage divider...well I have no idea to be honest. One of the electronics wizards on this forum can answer that one.
« Last Edit: January 19, 2009, 03:40:09 PM by householdutensils »

Offline Soeren

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Re: Properties of a microphone
« Reply #2 on: January 19, 2009, 04:54:26 PM »
Hi,

It's an electret condenser microphone capsule http://en.wikipedia.org/wiki/Electret_microphone
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline TrickyNekro

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Re: Properties of a microphone
« Reply #3 on: January 20, 2009, 12:28:11 PM »
It's not so easy to play with such microphones....
Yes their basic concept of function is vibration and "resistance" variation (it's not actually resistance.....)
You can easily attach a sound amp like LM386 and recreate the sound... BUT!!!
Converting it to a nice and reliable reading for microcontroller is quite a hell...
First at the output you place a grounded capacitor to eliminate digital noise...
Such noise is produced by the clocks of the microcontrollers and in
a sound pattern may create harmonics destroying your readings.... Bad!!!
Secondly you need to amp the signal with a audio amp as described above...
The IC used MUST have a clear power supply (free of noise)....
Basically making a battery for testing more than a necessity.... No ATX or el chipo wall adapters....
More over you filter again the signal with capacitors connected to the output of the audio amp
and the input of the next device....
Then... Having only frequency on the input you can use a frequency to voltage converter!!!
That's cool!!! Cause you basically by this way you don't let so such noise in the MCU...
Again apply filtering capacitors...
And finally connect the output of the freq to volt device to the MCU or a ADC....

All this have you in a need of a good scope and knowledge of filters....

And remember... This is only for reading the mic... no voice reckon and such....
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

Offline Soeren

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Re: Properties of a microphone
« Reply #4 on: January 21, 2009, 04:19:54 AM »
Hi,

wow sounds complicated     ???.  cool though
It ain't!
As long as the circuit is properly decoupled (and filtered if needed), it's plain sailing.
Key points are: Design well, build well, box well :)
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline spykid99

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Re: Properties of a microphone
« Reply #5 on: January 22, 2009, 05:23:10 AM »
Its a electret mic
You can simply put a high gain amp and plug the outputs to a computer or MCU
Ive got a  schematic in a book ill try to upload it ASAP

Spykid99
"Do not worry about your difficulties in Mathematics. I can assure you mine are still greater." ~Albert Einstein

 


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