Suitable power supply for Arduino Mega and motor shield

I’m trying to build a Digital Command Control for a model railway utilising an Arduino Mega and a Motor Shield. I’ve been told I need a suitable power supply of between 7 - 9 volts DC to operate the Arduino Mega and then a separate 14.5V DC 3A supply to supply traction current via the motor shield.
Have you any suggestions for suitable units please.

Hi Rob,

Thanks for posting on the forum!

Which motor shield are you currently using, do you have a link to it or a SKU? Many also include regulators on their input power supplies to back power your Arduino when they’re connected and on our site they often also include a recommended PSU (sometimes a few depending on your load or connected devices).

Hi Bryce,
According to my original order, the Motor Shield had an sku of A000079.
I’m basing my query on the info provided on the DCC++ EX website (, which a friend has sent me.
This details the requirements to build a unit using the Arduino Mega 2560 R3 and the Arduino Motor Shield to provide DCC control for a model railway. The locomotives are equipped with suitable DCC decoders that operate the loco and other functions as required. (Lights, sounds etc.)
The info talks about using two separate power supplies - one for the Arduino Mega 2560, which has lower voltage & current requirements (They say 7-9 volts as there is a 2V voltage drop in the Arduino voltage regulator), and one for use with the Motor Shield to provide power to run the locomotive. There is appropriate software uploaded to the Arduino Mega 2560 which in conjunction with other control ‘throttle’ software is used to control the locomotives. They suggest this power supply should be capable of providing around 14.5 volts at 3 Amps as the Motor Shield would drop the output voltage by around 2 volts.
I must admit to understanding the principles but I’m not good on the specifics.

Hey Rob,


All good should be pretty quick and easy to hook up a couple of power supplies to this board to power your motors and Arduino. You’re right, you need to provide two separate power supplies in this case, the first for the Arduino can be connected to the Vin and Gnd pins that I have identified with a square on the image above, or you can use the barrel jack on the Arduino which is connected to the same lines and just use a 9V PSU with a 2.1mm barrel jack connection on it:

Now we’re out of stock of this 24V version at the moment, but an adjustable 24V switchmode plugpack is probably the way to go, I’ve linked one that Jaycar carries that should do the trick. You should be able to use one for the Arduino, and the other for the motors power supply once adjusted to the appropriate voltages, just ensure that they can kick out enough current for your motors at stall and you should be golden.

By the way, here’s a barrel jack to screw terminal adapter so that you can hook it up to the power supply a little more cleanly than having loose wires around.

Thanks for the detailed info Bryce.

I have become interested in model trains recently and have briefly looked at what is required.
While my electronics experience would enable me to build a 14.5V 3A supply; it may be better for you to source something from a model railway supplier. Something that plugs into the mains, is safe and produces 14.5V 3A output.

Plug packs are not going to give 3A; at best 1.5A. The switchmode supplies older laptops used might work, these were around 15V and may provide up to 3A.

Check the Meanwell web site, they have many power supplies and their products have a good reputation. But they are not cheap and some have exposed mains connections. Be careful.


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Hi Jim,
Yes, the DCC website my mate pointed me to ( talks about using laptop style ‘brick’ power supplies with voltages/current of what is required. My understanding is that the amperage only limits the number of locomotives you can operate using DCC, so theoretically 1.5A would be sufficient for one loco hauled train.
Thanks for the power supply info - I will check it out.