Arduino + motor driver shield output power?

what is output voltage (that voltage that goes to motors) in this set up (arduinos input voltage is 9v)


arduino motor driver shield

The motor shield uses the L293D darlington H-bridge, so the motor(s) get about 2 to 2.5V less
than the motor supply voltage.

You need a powerful enough motor supply to operate motors, a small 9V battery is not
able to source enough current.

In general you should run the motor from a separate supply to the Arduino if you want
the Arduino to run reliably. That motor shield probably has a jumper to set whether the
motor supply is commoned with Vin on the Arduino or not.