user26717: Scenario:
I have a functioning weather station (temp/humid, MQ-2 smoke sensor, anemometer), and want to add a barometer.  The weather station is outside, linked to my inside display and RTC by the I2c&Power modules and ethernet cable.  The cable supplies 12v and I use a small converter to provide the 5v to run the I2c&Power board and the rest.  
So I have 12v and 5v available out at the weather box.
Inside along with the RTC and LCD display I have a 2-port I2C&Power which will be used in the future (with the new pgpio library) to feed the info to an Rpi3 to create a web page to show changes over time.
The barometer module I bought is the BMP-180.  It is nice and tiny and looks perfect for the job, but the instructions all over the web tell me that it will burn up if powered by 5V.  The Arduino Nano does not have a 3.3v output pin like the Uno does.  
Q:  What is the easiest way to accomplish adding this 3.3v board to the weather station?

user26717: Here is the solution I settled on:  a small part that will step 5 volts down to 3.3 volts.  The price is right, but it will be shipped by the slow boat so will take a month or so to receive.
5Pcs 5V to 3.3V DC-DC Step-Down Power Supply Buck Module AMS1117 LDO 800MA
http://www.ebay.com/itm/5Pcs-5V-to-3-3V-DC-DC-Step-Down-Power-Supply-Buck-Module-AMS1117-LDO-800MA-/261983164332
It has 3 pins - Vin, Vout, GND.    Easy to hook up.
Upvote to everybody for the discussion.

user3917: Consider attaching your +5V supply to a USB plug, and using that to power the Nano via its USB socket.
When the Nano is powered via its USB socket, the CH340 or FTDI FT232 supply  up to 50mA of 3.3V power to the 3V3 pin located between Aref and d13.  See for example 3v3 output from FTDI chip on Arduino Nano 3 at arduino.cc.   
Actually, that thread apparently says the 3V3 is available no matter how the board is powered; you may want to run some tests and measurements.  The only test I ran was to measure about 3.2 V at the 3V3 pin when a clone Nano 3 with CH340 was connected to a USB-power adapter.

26717: <h2>Scenario:</h2>

<p>I have a functioning weather station (temp/humid, MQ-2 smoke sensor, anemometer), and want to add a barometer.  The weather station is outside, linked to my inside display and RTC by the I2c&amp;Power modules and ethernet cable.  The cable supplies 12v and I use a small converter to provide the 5v to run the I2c&amp;Power board and the rest.  </p>

<p>So I have 12v and 5v available out at the weather box.</p>

<p>Inside along with the RTC and LCD display I have a 2-port I2C&amp;Power which will be used in the future (with the new pgpio library) to feed the info to an Rpi3 to create a web page to show changes over time.</p>

<p>The barometer module I bought is the BMP-180.  It is nice and tiny and looks perfect for the job, but the instructions all over the web tell me that it will burn up if powered by 5V.  The Arduino Nano does not have a 3.3v output pin like the Uno does.  </p>

<p>Q:  What is the easiest way to accomplish adding this 3.3v board to the weather station?</p>
 26717: <p>Here is the solution I settled on:  a small part that will step 5 volts down to 3.3 volts.  The price is right, but it will be shipped by the slow boat so will take a month or so to receive.</p>

<p>5Pcs 5V to 3.3V DC-DC Step-Down Power Supply Buck Module AMS1117 LDO 800MA</p>

<p><a href="http://www.ebay.com/itm/5Pcs-5V-to-3-3V-DC-DC-Step-Down-Power-Supply-Buck-Module-AMS1117-LDO-800MA-/261983164332" rel="nofollow noreferrer">http://www.ebay.com/itm/5Pcs-5V-to-3-3V-DC-DC-Step-Down-Power-Supply-Buck-Module-AMS1117-LDO-800MA-/261983164332</a></p>

<p>It has 3 pins - Vin, Vout, GND.    Easy to hook up.</p>

<p>Upvote to everybody for the discussion.</p>
 3917: <p>Consider attaching your +5V supply to a USB plug, and using that to power the Nano via its USB socket.</p>

<p>When the Nano is powered via its USB socket, the CH340 or FTDI FT232 supply  up to 50mA of 3.3V power to the 3V3 pin located between Aref and d13.  See for example <a href="http://forum.arduino.cc/index.php?topic=177059.0" rel="nofollow noreferrer">3v3 output from FTDI chip on Arduino Nano 3</a> at arduino.cc.   </p>

<p>Actually, that thread apparently says the 3V3 is available no matter how the board is powered; you may want to run some tests and measurements.  The only test I ran was to measure about 3.2 V at the 3V3 pin when a clone Nano 3 with CH340 was connected to a USB-power adapter.</p>
