> I believe it's a frame of 50 per second for it. Might want to=20
> check this out to be sure.  The standard is I believe 50 with=20
> a 15ms center point PW but I've been wrong before :)

Yes, your right, it is 50 per second or 20 ms. And a 1.5 ms pulse=20
should center the servo.

> For computing volume, I suggest first rectifying the input=20
> signal using a bridge to get your DC offset.  Then instead of=20
> using the linear voltage use a logrythmic scale to determine=20
> your magnitude.  You can find A-law and u-law linear to=20
> logrythmic scales on the net. I suggest you use there=20
> interpreted values.  Are you planing on 8/10/12 bits of=20
> resolution for your input sense? The other option is more=20
> complicated that is putting a logrythmic amp in the signal=20
> path (and less useful). You want to basically get your=20
> numbers in some sort of db scale (I believe A-law matches=20
> this).  Then you can do it by 'eye', IE observe adjust and=20
> make it look right.

Okay.. Now we're getting into the part where I am lost at..=20

Lets see, your suggesting using a bridge rectifier to remove the=20
lower half of the wave so the voltage is all positive. That makes
sense. And then use a resistor to limit the Voltage to <=3D Vdd.=20

So that handles conditioning the audio signal for the PIC.. now the=20
hard part.=20

Then you suggest based on the voltage, use a logrythmic scale to=20
produce a value that is ramped up based on the amplitude. Okay..=20
couple of minor issues, I don=92t have the faintest clue about=20
logrythmic scales (beyond the fact that they are logrythmic:)
and implementing them in a PIC, and I don=92t have any experience=20
using the a/d converter. I am going to use a 16F877A for this=20
project. The data sheet indicates that it can do 8 or 10 bit=20
resolution. I am not sure why I would choose either one or the=20
other but based on what I understand, 8 bit would be more=20
then enough for sampling the audio signal, since I am only=20
updating the servo every 20ms, and the PIC can sample at=20
a much higher rate it appears. An average amplitude over=20
that 20 ms period (with many samples) would be great to=20
calculate and give the most accurate result, but one sample=20
of the amplitude every 20 ms is probably good enough for=20
this purpose.=20

Any websites, tutorials, examples I should look at to really=20
learn from scratch about implementing logrythmic scales in a PIC
and using the A/D converter at 8 bit resolution?=20
Anyone have any sample code they could share?=20
Can anyone else fill in some more blanks?=20
Ya'll are a big help to a newbie like myself. It seems=20
as though this project might just be possible based on the=20
help ya'll are providing.=20

> Sounds like fun, now all you need are servo's to make the=20
> eyes move and track using a pair of itnernet cams and you can=20
> have a nifty thing to freak the neighbors out. ;)

Heh.. that would be wild:) A bit beyond a PIC's capability to=20
track a moving object however. Actually.. something that might=20
be done with a PIC is to interpret a pair of microphones resulting
in a stereo sound, and using the difference between the sounds=20
to determine where to move the eyes to (left, right, or center).=20
Hmm.. Maybe that will be my next project:) Anyway, thanks for the=20
help so far.=20

Anyone else have any advice, ideas, howtos, sample code, working schemati=
cs:) Hehe. I need all the help I can get.=20

Thanks,=20
Mike
=20



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