There are quite a few LED things on AliExpress that claim to be WS2812 but require 12 V. (http://www.aliexpress.com/store/product/26mm-WS2811-LED-pixel-module-3pcs-5050-SMD-RGB-LED-DC12V-input-milky-cover-0-72W/701799_32333078034.html). Do they work with 5 V Arduinos (and FastLED) and an additional 12 V power source?
Yep, exactly!
Just be aware that not all of them have a shared ground; I’ve had a few sets where I’ve had to manually tie the grounds together rather than done on board.
Well, I decided against 12 V stuff. Using these nice 5 V power banks is too nice, while having two voltages sounds like pita.
When I do 12v setups, I use a single 12v source and power both the LEDs and the microcontroller from that.
Some Arduino boards (Uno, Leonardo, etc) have a power jack that can accept 12v, and they have an onboard power regulator that drops it down to 5v. Check the specs for your Arduino; you might be able to “just do” a 12v setup.
If not, a little external voltage regulator will give you 5v from 12v.
For small projects these are nice, 5V and 12V output but just 2A. https://www.sparkfun.com/products/11296
there are some nice 12v batteries I have been using with 12v led strips controlled with arduino mega, nano, pro and flora.
and the same as mark, feed both arduino and led strip from the battery, with a voltage regulator in between.
The required voltage depends on the number of LEDs in series. Some 12V pixels have 3R, 3G and 3B diodes connected to a single WS2811 IC, while others have a linear regulator dropping the input voltage to 5V which then drives a WS2812 package (or a discrete IC with a single RGB pixel).
The linear regulator type will generally accept voltage as low as 5.5V while maintaining full brightness. The lightsuits used for Kaiju Flambeaux Corps[1] used regulator-type “12V” pixels which were hooked up to a switching regulator outputting 6V (rather than directly to the 11.1V Li-po, which would have let the pixel regulators waste around half the battery’s energy as heat).