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Topic: powering the Arduino Uno with a 12V battery (Read 15725 times) previous topic - next topic

CrossRoads

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.

Daanii

#31
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.

CTE_T

Quote
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.


Quote
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.
I also have PIC related web domain.

CTE_T

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.

CTE_T

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

CTE_T

Can you provide a link to these batteries you use?

CTE_T

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

pasi

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

CrossRoads

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:
http://www.newegg.com/Product/Product.aspx?Item=N82E16875995200&nm_mc=KNC-GoogleAdwords&cm_mmc=KNC-GoogleAdwords-_-pla-_-NA-_-NA
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.

pasi

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:
http://arduino.cc/playground/Learning/LeadAcidBatteryAdapter
will it be ok if i use to the positive pole one fuse 1A?

Daanii

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.

PeterH

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.
I only provide help via the forum - please do not contact me for private consultancy.

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