How to split the voltage for arduino and motor?

Hi people!

if i have a newbie question, it might sound kind of stupid for you, but i have no idea what is the ideal way to do this..

well, lets say i have an arduino and a 12V dc motor, i would like to have both of them working from the same power adapter but i don't know what rating of a power adapter i should get, and how do i split the power between them?

I assume that arduinos work on 5V on about 500ma (like the usb connection?) my motor could probably work well with 12V at 1A, how can i give power to them both from the same adapter?

Thank you!! :)

All you need to is connect the 12V to both - use the power connector on the arduino, the onboard regulator will make the 5v it needs. The 12V will go the motor+, the motor- will go thru a transistor that an arduino output pin will control. Search the forum, there are examples out there.

The USB interface may have a 500mA fuse but that’s just for protection against stuff ups.

Your Arduino won’t use anywhere near that much. I’m sure it’s documented somewhere but I’d say maybe 10-20mA + loses in the regulator + whatever it’s driving which in your case will be not much because you’ll be driving the motor with a transistor.

So you can use a power supply (PSU) of say 1.5 or 2 amps.

The Arduino has an onboard regulator, so to run them both from the same PSU just connect the PSU to both the Arduino and the motor.

To find out how to drive the motor have a look at Grumpy_mike’s great tutes (can’t think of the URL right now) but I’m sure he’ll see this.


but I'm sure he'll see this

Yep right:-

I would allow 30mA for the arduino and the rest for the motors. The currents simply add up despite there being at different voltages because the regulator makes the 12V into 5V but 30mA is still needed as a current.

The spec for the boards doesn't advise going above 12V because of the risk of the on board voltage regulator overheating but it can go up to 20V, so you should be okay.

Great! thanks everybody!

I appreciate the answers! :slight_smile: