You can control these 3V motors with those shields, but you will need to use PWM to generate an effective voltage of 3V or less. For example, if your Vin is 9V then a 33% duty cycle on the PWM output will drive the motor the same way as if you had applied only 3V.
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons
Now comes another question, when i use one of these Motorshields i can use a 12v DC Motor, but to provide the 12v i have to connect the Vin and Grnd from shield/arduino to a 12v Battery correct?