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[on:]

i am sorry if this is the wrong place to post this, but i do not really know what category this would be in. it is more of a general question.
this may be a dumb question, but it is one that i could not find an answer to.
can i power the arduino uno with 5 volts on the Vin header pin? i know it says 6-20 are the limits and 7-12 is recommended, but it can be powered from usb. usb is only 5 volts. The reason i am asking is because i am making a project that is going to require a max of 2.5 amps. that is way more than the arduino can handle. so i bought two 5 volt 2 amp wall wart power supplies. it would be great if i could have those power supplies power everything including the arduino, but that may not be possible. i guess as a last option if i really wanted to, i could cut a usb cable in half and connect the power supplies to the usb cable, but i only have one of the usb cables the arduino uses. so if i used that for power, i would not be able to use it for data since it would be cut in half. so if that is what you guys recommend, i will buy another cable. i just dont want to if i can power the arduino from the power supplies directly. keep in mind that i am not trying to say that the power will come from the arduino for the project. the power supplies will be powering everything directly. i would just run wires to the arduino to power it. thanks in advance to anyone that helps in any way at all!

[Reply #1 on:]

"can i power the arduino uno with 5 volts on the Vin header pin?"
Yes.
Put a 1N4001 or comparable diode from +5 (cathode) to Vin (anode) to protect from reverse biasing the regulator.

"6-20 are the limits and 7-12 is recommended" at the barrel jack or at the Vin pin.

[Reply #2 on:]

"can i power the arduino uno with 5 volts on the Vin header pin?"
Yes.
Put a 1N4001 or comparable diode from +5 (cathode) to Vin (anode) to protect from reverse biasing the regulator.

"6-20 are the limits and 7-12 is recommended" at the barrel jack or at the Vin pin.

You mean no to the Vin pin and yes to using the 5V pin don't you?

Lefty

[Reply #3 on:]

Vin +5v 'pad/pin' can only take up +5v ( &this is by passing the +5v regulator ....correct??)






edit: corrected

[Reply #4 on:]

Vin pin can only take up +5v....correct?
(this is by passing the +5v regulator?)

i don't think so. from what i have read the Vin can only take 6 to 20 volts, and 7 to 12 volts is recommended. but i may be wrong.

[Reply #5 on:]

Yikes!..

I typed that backwards!  (sorry) (corrected)

no more than +5v to the "+5v pin(s)"..  which bypasses the voltage regulator..  

[Reply #6 on:]

Er...
Yes; put +5V on the 5V header pin, and a diode from 5V (cathode) to Vin (anode).

[Reply #7 on:]

I thought I read it was not a good idea to power from the +5v pins like that?  something about backwards powering the voltage regulator or something?  (Im trying to recall where I just read that.. some thread here perhaps?)   this true?

thanks..

[Reply #8 on:]

You did - back in reply #1.

[Reply #9 on:]

doh~!.       (thats what I get for having tons of tabs open and reading a bunch of threads here at the same time)

sorry.  lol

so its true then?  you should not?  (isnt that how many 'FTDI' breakouts work? powering the board in just such a way?)

[Reply #10 on:]

so i bought two 5 volt wall wart power supplies

Have you measured the voltage? Some of them are really crap i.t.o delivering what they say, and the usb must be within 4.75 and 5.25VDC (from memory, don't quote me on the figures) so you might like to be sure.....

(I have a wall wart with a switch for various outputs which gives something like 5 when it says 3.5, and 8 at 5 and blah blah...)

[Reply #11 on:]

i have not measured the voltage, but i will make sure to do that.

and if i use a diode, there is no chance i will mess up the arduino? i just never thought of powering an arduino from the output pin and the input. i never thought that was possible.