Battery powered arduino - problems with AnalogIn


my arduino is running with 9volt battery block and lm7805. i´m reading sensor data from a gyro sensor which is powered with 3,3volt (LD33). data is being read by max/msp and simple message system. as i recognized that during the time the values of AnalogRead changes with battery load. that seems pretty strange because 7805 should make sure that voltage (and of course reference voltage) is on constant level.


You don't need that voltage regulator. There already is one on the Arduino board.

i build up arduino on a breadboard, so i need it.

Do you have some 220uF or similar capacitors on either side of the regulator? Makes for a nice happy power supply, with better transient response.