I just want to confirm something before I wire up my first ever Arduino project and fry all the stuff I just spent money on.

It is my understanding that the Vin power input will tolerate a 9V battery and use voltage regulators to pare it down to either 3.3V or 5V (as different parts of the board require). So it is then my assumption that if I have a 9V battery running to Vin, that I could then connect a power wire to the 3.3V connector, and reliably get a 3.3V signal (and ditto for 5V), yes?

Or, is it that they are input jacks expecting either 3.3V or 5V signals? I guess I'm confused over this:

  • Will Vin then power the 3.3V and 5V inputs, giving me access to voltage at that level; or
  • Do I have to choose between 3.3V, 5V or Vin, and only use one of those to power my board (with the appropriate voltage level)
  • 1
    Have you checked the schematic yet? Jun 8, 2015 at 16:07
  • If you can provide a schematic I'll check it out and maybe it answers my question, but I'm so new to electronics, I may not even be able to make sense of it.
    – smeeb
    Jun 8, 2015 at 16:09
  • All Arduino product pages link to a schematic for the board. Jun 8, 2015 at 16:09
  • Then I would assume this is what you mean, in which case, I cannot at this exact moment make sense of it. And although I think I can guess your next argument, which is probably "Well then you need to learn how to read schematics, otherwise get out of electronics", I would counter-argue that Arduino is from the ground-up aimed at complete electronics newbies like myself. And that this is a basic usage question that should be answer-able without a moderate understanding of EE/ECE.
    – smeeb
    Jun 8, 2015 at 16:16
  • And yes, in time, I will learn this stuff, but I shouldn't have to be able to read that diagram and fully comprehend it to understand how to connect my board to a battery.
    – smeeb
    Jun 8, 2015 at 16:17

2 Answers 2


DC Jack is connected, through a diode, to Vin.

Vin is stepped down to 5V on-board.

5V is stepped down to 3V3 on board.

Thus you can do any one of the following numbered items.

  1. Connect a 7-12V supply to the DC Jack; thus:

    • use Vin as a supply @ DC - 0.7V for off-board peripherals, and
    • use 5V as a supply for off-board peripherals, and
    • use 3V3 as a supply for off-board peripherals.
  2. Connect a 6-12V supply to Vin; thus:

    • use 5V as a supply for off-board peripherals, and
    • use 3V3 as a supply for off-board peripherals.
  3. Connect 5V supply to the 5V; thus:

    • use 3V3 as a supply for off-board peripherals.

The above is only guaranteed for boards that follow the reference schematic, as plenty of clone/compatible boards do. If you buy a cheap Chinarduino and something doesn't work, or the thing breaks, after following anything above then that's your tough luck.


Yes your assumption is correct you can power 3.3v and 5v items from those pins as long as you don't take more current than the onboard regulator(s) can supply

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