electret microphone

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fran1942

New Member
Hello, am just starting out with electronics and would like to connect an electret mic to my PICAXE 08m2.
The purpose is to detect a babies cry, so it just needs to detect any type of audible noise and provide a signal to the 08M2 chip.
I understand that I will need to amplify the sound from the electret mic.
Can someone please direct me to or show me a simple circuit that will amplify the sound enough to provide a reading ?

Thanks kindly for any help.
 
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John West

Senior Member
Do a Web search for "electret microphone preamp." There are many out there. You'll likely need one. Find one with an adjustable output so it can be optimized for the PICAXE input. Also, it's handy to use one that will run on a single +5V power supply. It saves using a lot of additional parts.
 
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srnet

Senior Member
You will also find that Sparkfun sell a Microphone breakout board (has a pre-amp) if you dont want to build your own.
 
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fritz42_male

Senior Member
I'm having trouble with the Sparkfun microphone+opamp combo - I need to get a Scope on it to see what is actually happening. I can see variance in a connected LED when I yell at it but I cannot get the Picaxe to trigger reliably from it. Also this board has no trimmer.

http://www.sparkfun.com/products/9964

If anybody has got this working with a Picaxe, I'd be interested in the details.

You may be better off using a Sparkfun op-amp board and attaching a mic yourself. I have one but need to get round to trying it. This one has a trimpot on it.

http://www.sparkfun.com/products/9816
 
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fran1942

New Member
thanks guys, that is helpful.
Regarding the circuit that russbow and bgrabowski kindly posted; for my purpose of simply amplifying a babies cry to give an input to the Picaxe, I assume I would only need the basic amp part of that entire circuit ?
If so, specifically which of those indicated components would I need for my purpose ?
Thanks again for any help.
 
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premelec

premelec

Senior Member
I don't know if you've got this solved - there are three parts - one is a microphone [could be an earpiece or loudspeaker electret etc...] two is an amplifier to get the small microphone signal larger in voltage amplitude - the third is a rectifier to change the amplified sound to a dc voltage which will feed an input to the PICAXE. There are many sound activated switches on the market - these detect sound and put out a control signal - for a light or alarm etc. The circuit referenced shows an amplifier section with sensitivity control and simple output diode rectifier. Often times we now use operational amplifiers - an integrated circuit component with very high gain which can be adjusted with resistance feedback networks - A search on sound activated switch and operational amplifiers will give you lots of data. If you want to build the discrete transistor component unit that's fine - just usually a bit more trouble - your needs may vary but it's hard to know just what they are...
 
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meridian

Member
Baby monitor

fran1942 said:
Hello, am just starting out with electronics and would like to connect an electret mic to my PICAXE 08m2.
The purpose is to detect a babies cry, so it just needs to detect any type of audible noise and provide a signal to the 08M2 chip.
I understand that I will need to amplify the sound from the electret mic.
Can someone please direct me to or show me a simple circuit that will amplify the sound enough to provide a reading ?

Thanks kindly for any help.
Click to expand...
Hi, Have you looked at the commercial baby monitors? They will work out of the box, first time, no frustration. Of course there is the fun? of rolling your own but ... I have recently been through sound detection problems, see "Anchor alarm" thread. In the end I bought a sound detector kit and put the picaxe between the amplifier output and the relay.


paulr
 
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