user9842: 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)


user10003: 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.

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.

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.

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.

9842: <p>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.</p>

<p>It is my <em>understanding</em> that the <code>Vin</code> 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 <em>assumption</em> that if I have a 9V battery running to <code>Vin</code>, that I could then connect a power wire to the <code>3.3V</code> connector, and reliably get a 3.3V signal (and ditto for 5V), <strong>yes?</strong></p>

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

<ul>
<li>Will <code>Vin</code> then power the 3.3V and 5V inputs, giving me access to voltage at that level; or</li>
<li>Do I have to choose between 3.3V, 5V or <code>Vin</code>, and only use one of those to power my board (with the appropriate voltage level)</li>
</ul>
 10003: <p><code>DC Jack</code> is connected, through a diode, to <code>Vin</code>.</p>

<p><code>Vin</code> is stepped down to <code>5V</code> on-board.</p>

<p><code>5V</code> is stepped down to <code>3V3</code> on board.</p>

<p>Thus you can do any one of the following numbered items.</p>

<ol>
<li><p>Connect a 7-12V supply to the <code>DC Jack</code>; thus:</p>

<ul>
<li>use <code>Vin</code> as a supply @ DC - 0.7V for off-board peripherals, and</li>
<li>use <code>5V</code> as a supply for off-board peripherals, and</li>
<li>use <code>3V3</code> as a supply for off-board peripherals.</li>
</ul></li>
<li><p>Connect a 6-12V supply to <code>Vin</code>; thus:</p>

<ul>
<li>use <code>5V</code> as a supply for off-board peripherals, and</li>
<li>use <code>3V3</code> as a supply for off-board peripherals.</li>
</ul></li>
<li><p>Connect 5V supply to the <code>5V</code>; thus:</p>

<ul>
<li>use <code>3V3</code> as a supply for off-board peripherals.</li>
</ul></li>
</ol>

<p>The above is only guaranteed for boards that <strong>follow the reference schematic</strong>, 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.</p>
