duemi working fine with usb, but not stable with9v

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 !!

It sounds like your servos are pulling too much power to be supplied by your battery. The standard 9v PP3 type battery has a fairly limited power output, especially if its a zinc carbon rather than an alkaline.

oh k .. thanks for the reply.

I will power my servos separately using a 6v battery pack. Hope that will fix the problem.

Thanks again !! will update if it works !!