Project 03 - issues with 3.3v


I received my starter kit this week and got to the temperature sensor project. Everything worked smoothly with 5v so I decided to connect it to 3.3v version (as some people suggested). I also changed the code accordingly. And I started reading 1023 (maximum value) from my analog input. After spending 2 hours looking for obvious error I noticed I get exactly the same readings when I connect TMP36 to 5 or 3.3v. So it looks like I'm getting 5v from my input labelled as 3.3v (as the program scaled for 5v gives me the correct temperature when tmp36 is connected to 3.3v). Am I missing something obvious here? The circuit itself is very basic: usb cable from my laptop to arduino, then tmp36 connected to the gnd, analog input and 5v/3.3v. I would really appreciate your help, Jacek

I think it auto maps max reading to your max voltage, so all working well.

Thank you for answering. So if I understand your answer correctly after connectring TMP36 to 3.3v I don't have to call analogReference(EXTERNAL) nor use 3.3 when calculating the voltage from TMP36 sensor value? I was following articles similar to this: and they all mention otherwise.