# Power Supply With Battery Packs

I have a question about how to get a power supply from a battery pack to work on the Arduino. I'm new with robotics, so sorry if this question is noobish. Would a battery pack for 4 AAA batteries be enough to power it? And to hook up the battery pack to the DC plug, should I just take an old connector, strip the wire and connect it to the battery packs? Thanks in advance.

Would a battery pack for 4 AAA batteries be enough to power it?

No that would only give you 6V (nominal) which is not enough over the 5V for the regulators to work. On the other hand you could use 3 of them and feed them straight into the 5V. As the Arduino will work on less than 5V.

So 6V would damage the arduino? And the battery holder i have has 4 slots, so would the thing work with only 3 batteries? And could i add a resistor to take away some of the volts?

EDIT: the battery pack uses 4 AA batteries, not tripple A like i said before sorry

So 6V would damage the arduino?

No, operation would just be unreliable. The on-board voltage regulator would not be able to create a stable 5v. This would get progressively worse as the batteries start to die.

And the battery holder i have has 4 slots, so would the thing work with only 3 batteries?

As long as you replace the battery with some kind of jumper. Most battery holders expect a continuous circuit. An alternative might be to use rechargeable batteries. They tend to run around 1.2V per battery, so four of those would be very close to 5V.

And could i add a resistor to take away some of the volts?

That's not how electricity (and resistors) work. Resistors drop a voltage, based on the amount of current that flows through them. So as your Arduino project does different things, the resistor will be dropping different voltages. Additionally, the resistor is just going to burn (waste) power. Generally when you are running off of a battery, you don't want to just waste energy.

the battery pack uses 4 AA batteries, not tripple A

For the purposes of this discussion, that is irrelevant. They provide the same voltage per cell, just less power capacity.

As long as you replace the battery with some kind of jumper. Most battery holders expect a continuous circuit. An alternative might be to use rechargeable batteries. They tend to run around 1.2V per battery, so four of those would be very close to 5V.

Depending on what is meant by mattloto for the term "robotics", it might be best to simply use 7.2 or 9.6 VDC rechargeable packs that are used in the radio-control hobby. They are plentiful, fairly inexpensive, and lightweight. They will supply more than enough voltage for the regulator, as well as plenty of current to run the Arduino as well as extra peripherals (servos, drive motors, etc).

In order to use them in this capacity, you would want to create some form of "power distribution" system, where the battery can plug in using a standard mating plug for the pack, and has an output plug that will plug into the Arduino's barrel jack, as well as extra leads or plugs to power any other devices. Ideally this would all be implemented on a separate PCB, and there would be regulators implemented on-board to supply the voltages to the extra devices as needed, as well as perhaps a "raw" voltage source (clearly marked and positioned, of course).

:)

@James: thanks for the info.

@cr0sh: I never thought of having a battery pack to power the motors, but that seems like a good idea! The only thing is that the power distribution might be a little complicated for my "robot", which is pretty much 2 modded servos and soon a ping sensor in the front, but I'll keep this in mind for later projects.

I checked out the starting guide and saw the section about using a 9V, which would be easy and instantly available to me. And another power-related question, to power the servo (its the small one) would the normal PWR output be enough?

to power the servo (its the small one) would the normal PWR output be enough?

Servos are not powered by PWM, they are controlled by PPM (not PWM) and are powered direct from a power supply.

So I can't use the PWN output to control the Servo's speed? What about just the motor part of the servo (without the board)?

The only thing is that the power distribution might be a little complicated for my "robot", which is pretty much 2 modded servos and soon a ping sensor in the front, but I'll keep this in mind for later projects.

Nonsense. The power distribution system of a robot is one of the most important items! Don't neglect it!

You are likely going to need a separate power source for your servos and probably the PING sensor anyhow. Set up a larger battery as I noted: Go to a hobby shop, and they should have pigtails/splitters to allow you to split the output of a pack into two. Feed one of the outputs into the barrel jack of the Arduino. Hook the other output up to another 7805 regulator (plenty of examples on the internet as to how to do this properly - you could also look at the schematic for the Arduino) to supply power to the other servos and the PING. Alternatively, you could hook up another regulator - a 7806 - to supply 6 VDC to the servos, while the 7805 supplies the PING.

Finally - if you can find them - go for low-dropout regulators (the 78xx/79xx series are not low-dropout) if you can; there are near drop-in replacements available for the more popular 78xx series regulators, but you have to do some searching.

Good luck in your project, though - whatever method you use (if you wanted to simplify things - if the above is over your head - then use two battery packs - an R/C pack for the Arduino, and a separate 4.8-6.0 VDC 4-cell AA pack for the servos, and run the PING off the Arduino's regulator (that will likely be about all you can run off the Arduino's regulator - you don't really want to do this, but it can work).

:)

Hi, we are using ADP1613 to make our Arduino-compatible robots work with 3AAA batteries.

You can see the robots and the DuinoBot board here:

http://www.robotgroup.com.ar/web/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=7&category_id=1&option=com_virtuemart&Itemid=2&lang=es

They work, and the MCU does not hang even when the motors are externally blocked.

There is an step-up to provide the logic's 5V and another for the motor's 12V.

At full speed, following a line continuosly, the robots has an autonomy of one hour and half aprox. In classroom it's much more (due to the interrupted use), and when you plug the USB connector to program the robot, the MCU and sensors takes their 5V from there automatically, just like a standard Arduino does.

The schemmatics will be fully published in December/January (that's because we are working on the public documentation and in the site which is still in construction), but if you need them, I can upload something in a few days, or next week.

Regards! Julián http://robotgroup.com.ar/