Sparkfun Electronics WS2812 Breakout Hookup Manual page 18

Mean Well LED Switching Power Supply -
5VDC, 5A
 TOL-14601
Connecting an Arduino
This hookup is fairly straightforward. You can power the breakout board(s) using the Arduino's 5V and GND pins.
Then all you need is to pick a free I/O pin to send data to the LED. Let's go with pin 4. To link more breakouts
together, simply connect the output pin of one to the input of the next. Make sure each breakout also gets some
power delivered to it.
Protect your WS2812's!
In addition to the hookup above we recommend the following additions to help you get the most out of your
WS2812-based devices:
Add a Big Smoothing Capacitor
Before connecting the WS2812 to a power source, connect a big capacitor from power to ground. A cap between
100µF and 1000µF should be good.