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Topic: powering the Arduino Uno with a 12V battery (Read 57513 times) previous topic - next topic


Okay, that one seems to get power from the ICSP header with an onboard regulator, and looks to have a voltage divider for the Rx in line.
Nice little combination of parts.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


Mar 02, 2012, 06:34 pm Last Edit: Mar 02, 2012, 07:37 pm by Daanii Reason: 1

The board has a 3.3V regulator, but where does its power come from? Maybe someone else can figure it out.

As CrossRoads said, the power seems to come from the ICSP header.


Okay, that one seems to get power from the ICSP header with an onboard regulator, and looks to have a voltage divider for the Rx in line.
Nice little combination of parts.

Ah so. In that case, we're back back to square-1. The XBee has it's own 3.3V regulator, but the power
to it comes from the 5V pin on the ICSP header. And that's the reason why the 5V regulator on the
Arduino board is overheating in the first place. Back to (12V - 5V) * .25A = 1.75W, which is much too
much dissipation for smt devices, even DPAK, as noted many posts ago.

So, three choices:
1. run the XBee at low duty cycle, probably < 20%.
2. use the series-R to drop the voltage in the pathway from the 12V battery.
3. use a lower battery voltage, like 6 NiMH AA-cells.

so uhhhhh.......

1. How would I do this?

2. What is a series-R?

3. Can I power the arduino and the xbee and the shield for more than an hour on those batteries?


I suggest to use two switching regulators one for 5v, one for 3.3v.

The chips are cheap, and very easy to use. You do not need calculate things.
You can use nearly any ring core of decent size, just add any reasonable number of
loops, and use any kind of electrolytic capacitors you have around.

Maybe your efficiency won't be maximal possible, but the switcher ICs don't really take it crude.

One time I really made a circuit using some small cores, added a total random number of loops,
and it simply worked.

For small currents you do not need a cooling grid but you'd see that yourself.

If you want to stick with the linear regulator I suggest to use a 6v lead battery, not a 12v,
there is no point in it to heat off the extra volts.


So, lets say I used 6 AA 1.5v batteries to power my Arduino board now. That makes a total of 9v. I would take a wire from ground on the arduino to the negative end of a battery and then another through the positive end to another negative end for all 6 batteries and then go from positive to Vin? I've been doing some research and it seems like the components I showed you before have been powered by the Arduino in the past without a separate power source, and safely as well. Since I am having a very hard time trying to understand all the electrical parts being thrown at me, and the Arduino will take 5v-12v input through Vin, I am assuming since the Xbee will be powered from the Arduino safely and with enough power to operate, I will need no other parts than these 6 AA batteries wired together. And a previous post stated that the batteries should last a long time.


And I suppose we need to know that to find out how long they will last :/


Can you provide a link to these batteries you use?


If we had to order online, I would guess they would have some at those sites online too.


is there any problem if i power my arduino uno from DC power jack with a car battery?my battery is varta 12v L2 400/640A


Is it actually in a car?
The regulator may run really warm, depending on how much current is being drawn.
You may want to consider a mobile phone charger for its extra power filtering.
An example:
5V,1A, USB connector
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


i am going to plug it only when the car is already running and not at the start up.arduino will only supply 5 volts to two servo motors . I found this:
will it be ok if i use to the positive pole one fuse 1A?


As CrossRoads says, that will make the voltage regulator on your Arduino run warm. Especially if you are pulling enough current to run two servos. Better to use a 5 Volt source, like the USB output that CrossRoads recommended. They are more efficient, and will save your Arduino from the heat.


Car electrical systems are very noisy, you need to ensure that you filter the power supply to the Arduino to stop any spikes getting through. I don't think it's a good idea to power servos directly from the Arduino since a typical servo can take more current than the Arduino regulator is designed to supply. Better to give them their own regulator.


You guys may have forgotten something very important!

I was browsing and had the same or similar question about the Arduino Uno.  Just wanted you to remember that if you are powering the Arduino Uno R3 from a Car battery which is in a car while it is running, the alternator can drive the voltage up at the battery to nearly 14 Volts.  !3.8-14 Volts.

The regulator in the Arduino may not be enough to protect it from these voltages!  If the battery is not connected to the vehicle and the vehicle is running the voltages from the Alternator can go as high as 50-100 Volts. 


They are cheap and this way you don't have to find out the hard way buy having to buy a new Arduino Uno, losing all of your code, and/or having to start over!

I stress this because I am wanting to use the Arduino Uno to power 4 Relays which will turn on and off Lights when a LDR senses it is dark enough to turn them on.  The Arduino Uno will then power 4 5Volt Relays, which will then power 4 circuits of Lights if the ignition is on.  I needed to find out what the Maximum Voltage the Arduino can handle is.  I found my answer 12 Volts.  This raises concerns for the OP and myself and anyone wanting to power Arduino Uno R3 from a running car! 

Also some 12Volt Batteries are rated at 12-13 Volts just on their own. 


When Working with Arduino and Breadboards on an all nighter, Better buy some more Code Red Mt Dew... Know what I mean... X-)


I am trying to power an Arduino Uno with a 12v battery. The problem here is that the Uno uses 5v as its operating voltage and we need to use a power source that will last longer than an hour while sending wireless signals. A 9v battery will not last a full hour (as far as I know) so we are using a smaller version of a 12v car battery and need to convert the power to 5v and to last a long time. I've thought about using a voltage regulator, but 12v to 5v will seem to give a overheating problem. Also, the thought of using resistors as a voltage divider has brought up the fact that the battery may only last as long as a 5v.

Does anyone have any suggestions or comments on how to power the Arduino for a long time on battery power at 5v with little or no cooling?
[Hi how about your project ? do you use switching regulator to power up arduino using 12V battery ? please help me because i'm also gonna do a project named electric fence system]

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