NKC Motor Shield and 24V Motor Question

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:


Stop! Don't connect 24V to the Vcc. The Vcc is 5V.

The driver ic is the SN754410. That's a very common quadruple half H-bridge driver. It's almost the same as the older L293D.

It can handle 24V, so the 24V should go to that SN754410.
But you must not install the Vin pin, because the Arduino can have a maximum of 12V at Vin.

If you take a look at the datasheet of the SN754410, you see what VCC1 and VCC2 are for. VCC1 is for the logic and should be 5V. VCC2 is for the motors, and is 24V. The V+ in the schematic is the 24V.

The motor shield uses the 5V from the Arduino (Vcc).

You have to power the Arduino. You could use an adapter of 6...12V.
And you connect the 24V to V+ and GND of the motor shield.
Don't install the pin for Vin, and you are good to go.

But check everything very well. Start with 5V and then 12V for the motors, and measure if it is connected right.