I upcycled an old towel to make a messenger bag with an Adafruit NeoMatrix and an Arduino / 328Mega.
Inspired by Douglas Adams' Hitchhikers Guide to the Galaxy.
Step 1: Pro Mini and 3D Printed Enclosure
The Arduino and LiPo battery reside under a zip close "service flap" on the inside of the bag.
The bag is lined in denim to give a bit more structure and stability to the piece.
Two denim pockets were unpicked from old garments and sewn in, one for bag-user use, one for the chip under the service flap.
Step 2: Clear PVC Splash Cover
To keep everything usable in the case of torrential rain, I made a clear PVC slip cover to protect the electronics and to rain-proof the bag.
Step 3: Soldering Wires
The Neomatrix is an 8 x 8 ws2812 RGB LED matrix, there's only one set of pads to solder to.
One line for each of PWR, GND & Data.
I taped the trailing tails of the wires to the back of the matrix using insulation tape to reduce stress on the joint where they're soldered.
The matrix itself is hand sewn to the front flap of the bag, as it features pre-drilled holes. I used embroidery thread for this as it's quite thick and robust.