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.