battery power

My goal is to build something of an autonomous robot and therefore recognize the need for rechargeable power.

If I buy a typical battery used for RC cars, can I effectively use that to power both my Arduino and 4 or 5 servos?

Yes, you can.

Can you point me toward a schematic or diagram?

I don’t know if the servos would receive 5v through the arduino or whether the power from the rc battery would be somehow divided to power both the arduino and the servos independently.

The servo +5V lines and the Arduino +5V line get connected to +V of the battery. The grounds of the servos, the Arduino, and the battery all get connected together.

Powering the servos from the Arduino pin is generally not a good idea because of the current draw of the servos.

Powering the servos from the Arduino pin is generally not a good idea because of the current draw of the servos.

I can never find it when I look for it; maybe you'll know:

What is the maximum current draw for the 5V pin? :-?

5v pin is tied to the power, either usb or regulator

What is the maximum current draw for the 5V pin?

There's no single answer. The biggest factor is how much heat the voltage regulator can dissipate: some Arduinos (especially the "mini" versions) have small surface-mount regulators that can't dissipate much. Some (like most of mine) have TO-220 regulators that could even have heatsinks attached to them.

If you feed 12V into the Arduino, instead of 7 or 8V, the regulator has to dissipate more energy, so you can't draw anywhere near as much current safely.

The maker of your Arduino board should include some guidelines in the docs, but don't foget how much impact the input voltage has.

Ran

5v pin is tied to the power, either usb or regulator

Doh! Sorry...dumb question...definitely should have thought of that :P!

There's no single answer. The biggest factor is how much heat the voltage regulator can dissipate: some Arduinos (especially the "mini" versions) have small surface-mount regulators that can't dissipate much. Some (like most of mine) have TO-220 regulators that could even have heatsinks attached to them.

If you feed 12V into the Arduino, instead of 7 or 8V, the regulator has to dissipate more energy, so you can't draw anywhere near as much current safely.

The maker of your Arduino board should include some guidelines in the docs, but don't foget how much impact the input voltage has.

Cool, thanks. :D

The maximum draw from the onboard regulator is 400mA [edit]on the duemilanove/edit but that includes what the arduino is using.

Powering from a battery with a regulator is not normally thought of as a good thing becuase of the amount of power that is converted into heat by the regulator.

I would recommend a beefy 3.7 (high mAh) li-ion battery with a dc-dc step-up board to get it to 5v then just power the arduino through the 5v pin.

Mowcius