user62933: I have a Huzzah Feather ESP8266 (pinout) and due to the requirements of my project, I need to supply it with a 9V power adapter with a barrel connector, such as this one.  I'm REALLY new to all of this, so I am trying to figure out how to do this and understand reading dev board specs.
It looks like this development board has a regulator that will adjust a power source down to the appropriate voltage...  but how do I know what parameters it allows?
If I'm understanding correctly, on the pinout sheet above it looks like I would connect a power supply to the "VBUS" and "GND" (right?) pins.  It also says "500mA Max", so does that mean a 1A power supply won't work?  Also, why wouldn't it specify a maximum voltage?
If just connecting a barrel connector to those pins will not work, what am I missing that would get me there?

user31105: You cannot. If you look at the datasheet:
https://cdn-learn.adafruit.com/downloads/pdf/adafruit-feather-huzzah-esp8266.pdf
you can read all details on page 25/26:

Alternative Power Options
The two primary ways for powering a feather are a 3.7/4.2V LiPo
  battery plugged into the JST portor a USB power cable.
If you need other ways to power the Feather, here's what we recommend:

For permanent installations, a 5V 1A USB wall adapter (https://adafru.it/duP) will let you plug in a USB cable for reliable
  power
For mobile use, where you don't want a LiPoly, use a USB battery pack! (https://adafru.it/e2q)
If you have a higher voltage power supply, use a 5V buck converter (https://adafru.it/DHs) and wire it to a USB cable's 5V and GND input
  (https://adafru.it/DHu)

Here's what you cannot do:

Do not use alkaline or NiMH batteries and connect to the battery port - this will destroy the LiPoly charger and there's no way to
  disable the charger
Do not use 7.4V RC batteries on the battery port - this will destroy the board

The Feather is not designed for external power supplies - this is a
  design decision to make the board compact and low cost. It is not
  recommended, but technically possible:

Connect an external 3.3V power supply to the 3V and GND pins. Not recommended, this may cause unexpected behavior and the EN pin will no
  longer. Also this doesn't provide power on BAT or USB and some
  Feathers/Wings use those pins for high current usages. You may end up
  damaging your Feather.
Connect an external 5V power supply to the USB and GND pins. Not recommended, this may cause unexpected behavior when plugging in the
  USB port because you will be back-powering the USB port, which could
  confuse or damage your computer.



62933: <p>I have a Huzzah Feather ESP8266 (<a href="https://learn.adafruit.com/adafruit-feather-huzzah-esp8266/pinouts" rel="nofollow noreferrer">pinout</a>) and due to the requirements of my project, I need to supply it with a 9V power adapter with a barrel connector, such as <a href="https://rads.stackoverflow.com/amzn/click/com/B018OLREG4" rel="nofollow noreferrer" rel="nofollow noreferrer">this one</a>.  I'm <em>REALLY</em> new to all of this, so I am trying to figure out how to do this and understand reading dev board specs.</p>

<p>It looks like this development board has a regulator that will adjust a power source down to the appropriate voltage...  but how do I know what parameters it allows?</p>

<p>If I'm understanding correctly, on the pinout sheet above it looks like I would connect a power supply to the "VBUS" and "GND" (right?) pins.  It also says "500mA Max", so does that mean a 1A power supply won't work?  Also, why wouldn't it specify a maximum voltage?</p>

<p>If just connecting a barrel connector to those pins will not work, what am I missing that would get me there?</p>
 31105: <p>You cannot. If you look at the datasheet:</p>

<p><a href="https://cdn-learn.adafruit.com/downloads/pdf/adafruit-feather-huzzah-esp8266.pdf" rel="nofollow noreferrer">https://cdn-learn.adafruit.com/downloads/pdf/adafruit-feather-huzzah-esp8266.pdf</a></p>

<p>you can read all details on page 25/26:</p>

<blockquote>
  <p><strong>Alternative Power Options</strong></p>
  
  <p>The two primary ways for powering a feather are a 3.7/4.2V LiPo
  battery plugged into the JST portor a USB power cable.</p>
  
  <p>If you need other ways to power the Feather, here's what we recommend:</p>
  
  <ul>
  <li>For permanent installations, a 5V 1A USB wall adapter (<a href="https://adafru.it/duP" rel="nofollow noreferrer">https://adafru.it/duP</a>) will let you plug in a USB cable for reliable
  power</li>
  <li>For mobile use, where you don't want a LiPoly, use a USB battery pack! (<a href="https://adafru.it/e2q" rel="nofollow noreferrer">https://adafru.it/e2q</a>)</li>
  <li>If you have a higher voltage power supply, use a 5V buck converter (<a href="https://adafru.it/DHs" rel="nofollow noreferrer">https://adafru.it/DHs</a>) and wire it to a USB cable's 5V and GND input
  (<a href="https://adafru.it/DHu" rel="nofollow noreferrer">https://adafru.it/DHu</a>)</li>
  </ul>
  
  <p>Here's what you cannot do:</p>
  
  <ul>
  <li>Do not use alkaline or NiMH batteries and connect to the battery port - this will destroy the LiPoly charger and there's no way to
  disable the charger</li>
  <li>Do not use 7.4V RC batteries on the battery port - this will destroy the board</li>
  </ul>
  
  <p>The Feather is not designed for external power supplies - this is a
  design decision to make the board compact and low cost. It is not
  recommended, but technically possible:</p>
  
  <ul>
  <li>Connect an external 3.3V power supply to the 3V and GND pins. Not recommended, this may cause unexpected behavior and the EN pin will no
  longer. Also this doesn't provide power on BAT or USB and some
  Feathers/Wings use those pins for high current usages. You may end up
  damaging your Feather.</li>
  <li>Connect an external 5V power supply to the USB and GND pins. Not recommended, this may cause unexpected behavior when plugging in the
  USB port because you will be back-powering the USB port, which could
  confuse or damage your computer.</li>
  </ul>
</blockquote>
