I ferment beer. Well - the yeast ferments it, I drink it, but you get the picture.
While fermenting, the beer generates CO2.
The CO2 bubbles through an S-bend airlock that has a little liquid sanitizer in it.
When this happens, it makes a charming 'Bloop!' sound.
When this stops happening, it means that the beer is fermented and ready to be kegged or bottled.
I'd like my arduino to listen to the airlock so that it can tell me when the beer is ready.
I'm thinking a (cheap!) microphone on a clip or clothespeg, and a wifi-enabled arduino. A clip means I am not modifying the keg or putting anything into the wort and risking contamination.
What kind of microphone can I attach to a 3.3v arduino? Buy somethihng? Cannibalise an old mobile phone? How would I attach it - what electronics would I need? Could I put some sort of electronics in place so that I'm not attempting to analyse waveforms in software? Perhaps if I ran the microphone output through a diode and through a filtering capacitor, maybe, just to get a "sound/no sound" yes/no value?
The rest of the project isn't a problem - the programming, the web interface and so on. I can do that side of the project no problems.