Re: guitar tuner
hi again,
Shouldn't the voltage oscillate when sound hit it??
Yes. But, the signal direct from a microphone is generally quite weak. Also, if you used a voltmeter, that generally measures DC, or at least a very slowly changing voltage. Mic's can pickup from 20-20Khz (if they're any good) so, could our voltmeter measure a signal changing 20 times a second by a few mV?
Is this an electret microphone? The little 7-10mm mic insterts with 2 solder pads?
They have a small FET built inside, which is why they require power. This acts as a small preamp, since the voltage produced from a raw condesor mic element is extremely weak. That fet is just to get it up to a level where standard preamplifers can amplify it even further (so it can be plugged into a power amplifier for the speakers).
How does the mic produce a negative voltage when the only power I supply is 5V?
Believe it or not, this is actually a tough question
Sound, by deffinition is a wave of pressure, oscillating between 20Hz and 20Khz (actually beyond this range, but this is the range of frequencies we can hear/detect). When the microphone receives sound, it converts this rapid changing air pressure to an electrical signal. This signal oscillates according to the sound. So, say, for example, you're providing a 20Hz hum to the mic, and the mic is powered by 5v. Assuming the output of the mic is 1v p-p (these are just made-up values) then the output of the microphone would vary between 4 and 5 v. Now, that signal is really made up of two 'components'. A DC component (power) and a 'transient' component (audio signal). When this is passed though a capcitor, the DC ocmponent is blocked, and the AC/transient signal is allowed to pass. How much the AC signal is attenuated depends on the value of the capcitor. So, our DC component was 4.5V, and our AC component was 1v p-p (-0.5v to +0.5v).
Without the DC component we are simply left with the -0.5v to +0.5v audio signal.
When you measured the voltage of the microphone, did you connect a capacitor between the mic and the voltmeter?? I still doubt you'll see any change in voltage, but it should read '0v' and might jump around when you smack the mic element......which by the way, is inadvisable, as the little electret/condensor mics are quite fragile.
Heres some links to get you started........although....google is quite easy to use.
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http://www.ektopia.co.uk/ektopia/archives/2005/01/03/strobopick-guitar-tuner - wicked idea!!
http://www.acoustics.salford.ac.uk/acoustics_world/id/Microphones/Microphones.htm
http://audacity.fuchsi.de/forum.php?req=download&path=./edgar/electric/
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http://www.kingstate.com.tw/9-5.htm
hope some of these links help. The internet is a wonderful place.
BuriedCode.
ps: if the links come up '404 not found', copy and paste them into your browser.