Battery pack for Arduino Duemilanove

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,

I got my new Arduino Duemilanove recently and it came with a 9v adapter that needs to be connected to battery. In order to make my Arduino portable, what kind of battery do I need to buy ? Ideally rechargeable battery would be better. Can you please point me to the right type of battery ?

During development I was planning to use the USB port, but my Arduino needs to drive two stepper motors so I am not sure if USB can supply enough power. I have some AC-DC power adapters around with the following ratings

  1. 7.5VDC and 800mA
  2. 7.5VDC and 1Amp

Am I better off using these instead of USB if I want to drive two small stepper motors ?

Thanks,
RO.

2

Hello!

I think the appropriate answer would be: it all depends on the motors. You will probably be able to get your two stepper motors to move with the 500mA you get from USB, but they most likely will be very weak. At least that's what happened to me, when I did something similar.

The Arduino itself works with power supplies in external voltages between 7 and 12 volts, so your battery pack will need to be in that range (so your 7.5V rechargeables seem OK, personally, I'd go for 9V).

Also, the battery will need to supply the appropriate current to the stepper motors. Again, this depends on the motors (maybe you could look it up in the datasheet?) . The maximum current a battery is able to provide can be derived with some formula like voltage divided by internal resistance or something. In any case, I think most batteries will manage to drive the motors at least for a while. The more amh-hours on the battery, the longer it will last.

In addition to all that, if you're planning to put large currents through the Arduino, maybe you should consider using a relay or a transistor key instead? These elements would use a small current from the Arduinos to turn on or off the flow of a large current going through the motors.

What I'd actually do, is make an experimental setup and see if I can move the motors with those batteries I already own, and then all those difficult theoretical considerations would become irrelevant.

Good luck.