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Topic: Can I power the arduino with the power pins? (Read 1 time) previous topic - next topic

i_luv_arduino

Can I power the arduino with the power pins? Like can i just stick one wire in the 5v and the other to ground???


Krupski


Can I power the arduino with the power pins? Like can i just stick one wire in the 5v and the other to ground???


Yes you can. If you look at the schematic, you will see a MOSFET switch and associated circuit (comparator, etc..) that selects the voltage source automatically.

So yes, sticking clean, regulated 5 volts directly into the +5 pin and the ground pin is perfectly OK.
Gentlemen may prefer Blondes, but Real Men prefer Redheads!

i_luv_arduino

Thanks I didn't want to break it by overload of voltage, I just got it so thanks!!!
:) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :)

oric_dan


Can I power the arduino with the power pins? Like can i just stick one wire in the 5v and the other to ground???

Ehhh, this doesn't sound right to me. Some people say you can stick an external 5V into the
5V pin and power it that way [although I would NOT do it myself], but I'm not so sure that'll
be ok with "every" Arduino board. Some voltage regulators might not like it.

All in all, better to apply external power to the power jack or even the Vin pin, but of course,
then you'll need a power supply with at least 7V, in general. Also, external power should not
be more than 12V, although 7-9V would be better, to avoid the voltage regulators overheating.

MarkT

This has worked fine for me in the past, but I gather newer Uno's use an LDO voltage regulator that can't cope
with being driven from the output like this.  Anyone have chapter and verse on which versions of the Arduino
handle this?
[ I won't respond to messages, use the forum please ]

retrolefty

Well if you must power your board with a regulated +5vdc voltage source the safest way is to get an old USB cable and lop off the PC end and then strip out the ground and +5vdc wire and wire it to your power supply. Then you can just plug the cable into the USB connector and power the board the same way your PC does, plus you gain the protection of the on-board 500ma USB thermofuse.

Lefty

oric_dan

Why bother, sounds like a bunch of kluge-y jury-rigs that'll bite your butt one day,
especially if you forget which board has an agreeable v.reg. "Plug in here to blow
yer new $65 Arduino board".

LePaul

Which Arduino board do you have?

The schmatics should be available from where ever you purchased it.  It should show the input (VCC) and Ground (GND) and max voltage for that board.

Paul

oric_dan

Actually, I'd like someone to show me where the manufacturer's datasheet says it's ok to
reverse drive this voltage regulator.

Jackman


Actually, I'd like someone to show me where the manufacturer's datasheet says it's ok to
reverse drive this voltage regulator.


I have seen a schematic that the Vout of  voltage regulator connect to GND,and the GND pin output is -5v, of course the Vin is connect to 9v.
I think you can test it and you will get it.

fungus

#11
Dec 19, 2012, 12:41 pm Last Edit: Dec 19, 2012, 12:44 pm by fungus Reason: 1
The Arduino web site says:

Quote

Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.


See:  http://arduino.cc/en/Main/ArduinoBoardUno
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

retrolefty


The Arduino web site says:

Quote

Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.


See:  http://arduino.cc/en/Main/ArduinoBoardUno



Yes it states that but without details of a possible damage mechanism. The ironic thing is that when one is powering a Uno board via USB only then there is still +5vdc being applied to the output of the on-board +5vdc regulator which has no Vin voltage applied to it's input! So that is the exact same electrical condition as if someone was to apply an external regulated +5vdc voltage source to the shield 5v pin to power the board.

This subject, powering via the 5v pin, has come up a lot but there has never been a definitive answer to my satisfaction at least of how the on-board regulator handles external voltage applied to it's output pin by either USB or 5V path.

Lefty

oric_dan

Dear OP [i_luv_arduino], welcome to the wonderful world of electronics, where 20
different guys have 20 different opinions, LOL. Probably best to power your Arduino
boards in the "normal" manner - power jack, Vin pin, or USB.


fungus


Yes it states that but without details of a possible damage mechanism.


Maybe it's OK on the current revision but they want the freedom to be able to tweak the board.

If something dies they can then point you to the web site where it says "don't do it!".

Or maybe they're just trying to stop people connecting unregulated supplies to the +5V pin. A bit liel microwave oven manufacturers who say "don't put metal in microwave ovens!!" when in fact they're just covering their asses from people who'd put tins of beans in there otherwise.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

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