I recently purchased the NKC motor shield.
On their instructions they say this:
Motors can be any DC motor that can work up to the Vin voltage. Vin is the power supply voltage – 0.6V. If you are using a 12V transformer, then Vin is 11.4V. You can use a 12V motor. If you are using a 9V transformer, then Vin is 8.4V and you can use a DC motor rated at 9V.
The motor driver can support 3.6V to 36V motors (1A). But the shield is designed to take Vin from the Arduino / Freeduino power supply, before the 5V voltage regulator. You cannot supply Arduino / Freeduino with 36V without burning the voltage regulator.
If you need to use a motor rated < 7V or > 14V, you will need to modify the shield. Do not install the Vin pin header to the Arduino / Freeduino board (or install the Vin and GND pins upwards, to plug a connector from where you can supply this shield with a different voltage range than the Arduino / Freeduino board)… and install a socket and supply Vin in the Shield from a different regulated DC power source, using the same GND connection.http://www.nkcelectronics.com/arduino.html
I know I am just asking you to hold my hand, but this means that I would plug in the motor power supply of 24V to the VCC of the motor shield correct? Would I need to add any circuitry to allow the board to handle this level of power?
For info on the motor shield and the schematic go here: