I connected a 9v battery to arduino deumilanove. red goes to vin and black goes to ground.
I connected 5v pin to my breadboard +ve and the other ground pin on arduino to -ve of my bredboard.
This is not giving a stable power supply to my arduino .. but, if I check with my voltmeter .. it is showing >7v for 9v battery and that seems ok.
If i run the board using USB cable instead of 9v .. then board is running perfectly normal. even my servos were able to run at good speed.
wondering what might be the mistake I am doing? greatly appreciate your help !! Thanks !!