Controlling 3 Six Volt DC Motors with the Motor Shield

Hey everyone,

I am currently trying to power 3 DC motors (That need to be bi-directional) with my Arduino and Motor Shield. The end project idea is to have the Motors move independently from each other based on input to the Arduino. I currently have tested a setup with two of the motors in series with a 9 Volt power supply, as I do not currently have a properly rated power supply.

This is where my question comes in. What do you guys recommend when it comes to powering a setup such as this? Should I run the arduino and motor shield off of the same power or separate? If I run them off of one power supply going into the arduino's DC jack, what Voltage and current rating should I be looking for?

If I run them separately, I'm assuming I need a 7.2 Volt power supply for the shield (As I heard that there is a 1.2 Volt drop over the shield itself). Where could I find such a power supply?

I'm kind of at a loss for this portion of the project and truly appreciate any assistance!

One more question. I read that it is of particular importance to not plug the power supply in backwards when working with the motor shield. How can I be sure that one side of the power supply is ground and the other is positive before plugging it in and potentially destroying the shield/components?

Separate power is a very good idea. You can get 7.2 volts from 6 reachargeable AA batteries, they are 1.2 volts each. While you need 7 volts of more for the regulator on an Arduino board to be able to output 5 volts, I am guessing that is you use separate power you could drive the motor shield directly with 4*1.5 non reachargeable AA batteries for six volts.

You don’t mention the shield your using so I cant be sure. If you so use separate power, don’t forget to connect the grounds between the two power sources and watch the links in my signature for why you need separate power in the first place.

Duane B

Thanks for much for the response!

My only concern with using batteries is that the ladyada tutorials seem to suggest that they will not properly power motors. At least not for long.

I am using this motor shield I think that powering the arduino via batteries is just fine, but that the current pull from the motors might be too much for the batteries to handle.

Hi, Good AA batteries are surprisingly strong, I use the rechargeable ones in one of my 1/18 th scale race cars. Try ones designed for cameras and you may be surprised how good they are.

If your project is heavy or has a lot of drag you may need to skip the AA batteries an go straight for hobby batteries. Look at LIPO batteries, they are more expensive and need a computerised charger that will also cost around 40 dollars but they are very powerful and very light.

As AAs are so cheap to try, try them first.

Duane B.

I certainly will try the batteries. Thanks for the advice on those. If you want any technical specifications on the motors, they are 6 Volt DC motors with ~400 milliAmps of current pull under max load. If they do not work with the batteries, are there any cheap alternatives that you might see working? Or are heavy-duty batteries the next logical progression?