Maybe you could try connecting the Aref pin to the 3.3V pin. This one has a second voltage regulator, so it won't be influenced by the 5V circuit.
Change your resistor ratio, and add this line to your setup:
analogReference(EXTERNAL);
Maybe you could try connecting the Aref pin to the 3.3V pin. This one has a second voltage regulator, so it won't be influenced by the 5V circuit.
Change your resistor ratio, and add this line to your setup:
analogReference(EXTERNAL);