Need advice - Using a microphone for audio detection

SN96 · 2005-12-09 00:23

Hello guys,

I have a project where I want to take a custom designed robot head and give it sight, speech and audio. Right now, the challenge is the audio. I did a search on the Parallax forums and the closest thing that came up was an electric guitar tuner but it is more advanced than what I need. All I want to accomplish is for the stamp to do something if it hears audio on the left side or audio on the right side. For example, if I clap my hands on the left side, I would want the head servo move to the left.
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Here's a circuit I found from a link Paul Baker provided in that guitar forum. Would this circuit work?

····· · vcc
······· · O
········ ·|
··········/
········ ·\· EQUAL TO REQUIRED IMPEANCE
········ ·/· EX.= 1000 Ohm
········· \
········· |
········· |···· CAPACITOR MOST ANY VALUE 10uF 16v
|---|·· |···· +
|·· |---0----| (

·· AUDIO OUT
|·· |
|·· |---O

|---|··· |
········· ·|
········

········ ·---
···········-

Here is the one I want to get from Radioshack:

Here are some quick specs:

This omnidirectional microphone element has a wide 30-15,000Hz frequency response. Requires 4-10VDC.

Omnidirectional condenser microphone
Wide 30-15,000Hz frequency response
Electret Microphone Element with Leads

Here·are·the images of the ·bot head I am designing, that the two microphones will mount to.

Thanks for any help at all.

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Mike

Post Edited (SN96) : 12/9/2005 12:47:27 AM GMT

Lightfoot · 2005-12-09 01:45

Have you seen those clapper circuits that toggle a relay and/or an LED? Have the Basic Stamp or whatever you are using listen for a high signal come from that clap circuit. Have the stamp cut power to the clapper after the robot head moves to the left/right/whatever.

I put this kit together at one time (see link):

electronickits.com/kit/complete/elec/ck1607.htm

Post Edited (Lightfoot) : 12/9/2005 1:49:26 AM GMT

Bean · 2005-12-09 01:54

You will probably need an op/amp to amplify the audio signal, I don't think it will be powerful enough for stamp to detect.

microphone circuit -> op/amp -> diode -> cap -> input pin

Connect the + lead of the cap to the diode (forward biased), and the - lead of the cap to ground.

When a sound is detected it will be amplified and "charge-up" the cap through the diode, when it reaches 1.4V, then the stamp can detect that the pin is high. After detection make the pin LOW for a millisecond or two to discharge the cap. Then make the pin an input again, and your ready to detect the next sound.

Should work...

Bean.

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http://www.parallax.com/detail.asp?product_id=30012

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http://www.parallax.com/detail.asp?product_id=30015

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SN96 · 2005-12-09 02:36

Thanks Bean!

Just to clarify that I understand you, the circuit I need to design is like this?

····· vcc
······· · O
········ ·|
··········/
········ ·\· EQUAL TO REQUIRED IMPEANCE
········ ·/· EX.= 1000 Ohm
········· \
········· |
········· |···· CAPACITOR MOST ANY VALUE 10uF 16v
|---|·· |···· +···························· Diode··Cap
|·· |---0----| (

·OPAMP

<|----|(----o>>>·to stamp I/O pin
|·· |
|·· |---O

|---|··· |
········· ·|
·········GND

What pin # should the mic connect to on the OPAMP? If I am way off base, could you type the proper circuit if it is not to much trouble?

Thanks

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Mike

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Bean · 2005-12-09 03:04

Okay I really suck at ascii art, but something like this...

     vcc  
      O 
      | 
      / 
      \ EQUAL TO REQUIRED IMPEANCE 
      / EX.= 1000 Ohm 
      \ 
      /   CAPACITOR MOST ANY VALUE 10uF 16v 
|---  | +                      Diode 
| |---0----| (------- OPAMP------|>--+----->>> to stamp I/O pin 
| |                                  | 
| |---O                            ----- CAP 
|---  |                            /---\ 

      |                              |  
      |------------------------------+ 
     GND

You can use the opamp as inverting or non-inverting it doesn't matter. Inverting configuration is more common.
You will have to mess around with the gain to find a good value.

For the opamp, you will probably have to bias the "+" input to 1/2 the supply voltage (2 10K resistors).
Then run the mic input through a 10K to the "-" input, and also connect the "-" input through a 100K to the output.
That will set the gain at about 10 again you might have to adjust the 100K value to get good results.
Do a google search for audio opamp circuits and you should find several that will work.

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"SX-Video·Module" Now available from Parallax for only $28.95

http://www.parallax.com/detail.asp?product_id=30012

"SX-Video OSD module" Now available from Parallax for only·$49.95
http://www.parallax.com/detail.asp?product_id=30015

Product web site: www.sxvm.com

Those that would give up freedom for security will have neither.

Post Edited (Bean (Hitt Consulting)) : 12/9/2005 3:10:12 AM GMT

steve_b · 2005-12-09 12:47

Any VOX circuit shoudl work too....a guess!

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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

SN96 · 2005-12-09 15:07

Thanks Bean,

I am going to buy the parts and bread board test this circuit. One more question though, do I make this circuit for each mic I plan to use(two seperate circuits)? I want to·use 2 mics, one for the left side, and one for the right side. Or do I use the same Op AMP, but just connect the mic(s) one to the - input and one to the + input?

I am going to try the LM741 Op AMP.

Thanks!

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Mike

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Need advice - Using a microphone for audio detection

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