Making an LED hoodie involves lots of small fiddly bits, moving parts, and lots and lots of wires.  In order to make success more likely you will definitely want to test your components at each step of the process, so you don't spend hours of time soldering only to find that it all mysteriously doesn't work.  Testing at each step means you'll catch any shorts or mistakes early.  Plus you get to see your lights come on right away which makes the whole process much more fun and satisfying.

My favorite way to test is using a Gemma microcontroller and some alligator clips.  The Gemma is inexpensive and really easy to use for prototyping.  You can test any combination of wires without soldering or mucking about with breadboards and headers.  

If this is your first time using Arduino

Check out the getting started guide here.  You'll need to make sure you have Adafruit's boards installed as well as the Adafruit Neopixel library.

Plug your Gemma in to your computer using its USB port.  Open your Arduino IDE and select Adafruit Gemma from your Boards menu.

Go to File > Examples > Adafruit_Neopixel > strandtest and open the strandtest code.  Find these lines at the top:

Change PIN to 1.  

Change the first parameter in your strip definition to reflect the number of pixels you are planning to use:

Press the Reset button on the Gemma to get it into bootloader mode, and then immediately press the upload button in Arduino to upload the code.

Then, get your alligator clips out and hook them up thusly:

• Red > Gemma Vout
• Black > Gemma G
• Yellow > Gemma D1

The clips' colors will correspond to the wire colors used in the rest of this project.   You can power the Gemma from the USB port or plug a battery in to the JST connector.

Use the tester at every step of the way.  Use it to test a neopixel strand right out of the box to be sure all the pixels work.  Use it whenever you finish soldering together a batch of pixels.  Catch any mistakes early!