I have could decrease the fluctuation. Now, with the battery supply, I am getting values between 56-63. But these should be around 22-23 degrees. With the FTDI USB, that supply 3.3V, I do: read = read * (3.3/1024.0); and I get the correct 22-23. The battery supply provides 5V. In adittion, I am using the internal reference with the rule of thrre I show in the last post. It seems to be that the ADC is not using Vcc as the reference, why?
Thanks!