Feather Setup

Power comes in through the screw terminal and passes through the on/off switch, then splits to go to the Feather (via the JST port) and also to the LEDs. This is a safer way to power a large number of lights, since it doesn't pull all the power the lights require through the delicate electronics in the Feather.

NeoPixel Strand Setup

Each NeoPixel ring is connected to 4 wires: power, ground, data IN, and data OUT.

The power and ground wires all connect together to a "power rail" which runs the length of the strand. We'll wire all the 5v pins on the rings to the red wire, and all the g pins to the black wire.

The data wires are doing something a little trickier. The first data IN on the ring is connected to GPIO pin 12 on the Feather. The data OUT pin on this ring then connects to the data IN pin on the next ring in the series, and so on down the line. 

I've used a 3-pin JST connector (not shown in the diagram) to connect the strand of lights to the microcontroller and switch. This is optional, but allows me to easily remove the Feather from the strand in case I want to update it or borrow it for a different project.