[moved] Problem while using arduino motor driver shield.

[Sambhav_1]

Hello
I am building a project in which I am using arduino along with it motor driver shield for driving DC motor.
I am using a 13v transformer based power supply which is given input to the shield.
If i connect supply to shield then the voltage shield is same (~13V) but when i use along with arduino the input voltage measured at shield is ~5-6V.
Also, i measured the input impedance of arduino and its shield to be ~2K ohms and output impedance of supply ~2.5Kohms.
Please help me with this.
Thanks

 

[MD_SHAHRUKH]

Is the supply voltage converted to DC power? If It is not rectified then where would the ground pin attach? have you checked the voltage across the output while enabling the input?