I wasn't sure to post this in this section. I searched for the term and I didn't found useful information so I hope that this post is not repeated.
Also before post I read the Analog to Digital conversion part of the atmega168 datasheet and it says literally that input range is 0v - 5v.
I'm not an electronic engineer so don't be rude
I successfully wrote a program to the freeduino that uses an LCD and four 7-segment-displays to "measure temperature" from a LM35DZ sensor (http://labombiya.com.ar/images/DSC01066.JPG
Actually, that value it's not converted. I also read the libraries docs, and I already know that the integer value returned from analogRead() it's ranged from 0 - 1023 with aprox 4.9mV per unit.
I'm aware of all what software concern but I'm disabled of the hardware part
Maybe I'm missing a hardware-trick to scale the voltage so -55mV will be 0mV and units will be changed.
LM35DZ is not capable of measuring below zero degrees, or at least that was what I read in a datasheet, but a professional friend mades me a schematic that it would be possibly to extend the low-end range of the sensor (http://labombiya.com.ar/images/temp.jpg
(Don't look at the sch chip, it was illustrative from the autor with the caps too)
The thing is, if I get from ADC2 negative supply...what actually happens? I mean, datasheet says that the ADC input voltage range is 0v to 5v, and lib docs says that analogRead() returns an integer from 0 to 1023. Will analogRead() reads a value? Can I damage the input pins?
To be more abstract. Forget about my specific situation and think about a lm35 with full range configuration. That is, -55mV to 1500mV. As datasheet says, -55ºC to 150ºC. Seems the trick remains in making the scale, for instance, 0mV - 1555mV, being 0mV the low-end range, -55ºC. Am I wrong? I can't ask my friend he's busy on another things and he already helped me a lot. So I try not to bother him right now.
I'm testing empirically anyways. I recent put the lm35dz in a ziploc bag into the freezer. I'll watch for the results later on.
Thanks for your help, and btw, i didn't want to post in my previous post because the discussion was not directly related with my doubt.
Have a nice burning! xD