AVR-Chat

There has been lots of good advice given here on ADC.  One other 
place to look is the sensors.  I used a slightly different version 
this sensor and found that it can generate eratic DC values in 
certain circumstances.  In particular, I had mine mounted about 4 
inches above the floor and it was picking up ground reflections.  It 
looked like 3+ LSB of noise to me but when I moved it away from the 
floor or pointed it about 5 degress above the horizon, the "noise" 
was significantly reduced (down to about 1.5 LSB).

also, do you have supply filter caps on sensor V+?  I'm using 33 uFs 
and have seen designs with even bigger.  If I were to design them in 
again, I'd put in a seperate regulator for their supply V.

Phil