Turn Up the Bracelet

I usually listen to music while I'm working. Recently I changed my computer equipment and now the laptop and speakers I use don't have a good old fashioned volume knob to turn up (or down) the volume of the music. They have touch buttons you can press but that's not the same thing.
As a homage to the volume knob I miss so much I decided to create a whole bracelet around a volume knob. It won't change the volume of the music but it will change the color of the lights in the bracelet.

1. Adafruit Trinket - Mini Microcontroller - 3.3V
2. Lithium Ion Polymer Battery - 3.7 100mAh
3. 10K Linear Potentiometer
4. Slim Metal Potentiometer Knob
5. NeoPixel Mini PCB - Pack of 5
6. JST-PH Battery Extension Cable - 500mm
7. On Off Switch
8. Solderer, Wires, Wire cutter, etc...

The bracelet is made up of 2 parts. One is the main bracelet with a cavity for all of the electronics and one part is the top cover that slides in and covers up all of the wires and all.

I did various test with kappa material to get the the right size and shape for the bracelet. It is the smallest I could come up with that can house all of the parts and still be comfortable on your wrist.

Attached are the Solidworks files and STL files. I did need to sand them a bit so that everything would fit in.

I hooked up the 4 chained NeoPixels to pin 0 on the Trinket and the potentiometer to the pin that is marked 2 on the Trinket. In order to analogRead() from the potentiometer is is defined as pin 1.

The program is quite simple, it gets the value from the potentiometer and calculates the right RGB numbers based on that value. I wanted there to be a smooth transition between colors. I also set the brightness to the max at 255.

Attached is the code I wrote. I'm using Arduino version 1.6.6

Also see the video of how it works while it was still connected to the breadboard.

You need really tiny fingers and alot of patience to get everything right. I also suggest a good solderer with a thin tip and the smallest possible working wires to hook everything up.

I used 4 Neopixels, you can see how to wire them together here.

The on/off switch is connected to gnd and cuts the power line between the battery and the board. There's a backpack adafruit sells the can be used to connect the battery or you can just solder the wires to the exposed points on the back. For an example, check this out.

Its best to first put the potentiometer into the bracelet shell and put the knob on top to secure the position. Potentiometers come with a smaller extruded part for chaining them, I prepared a small hole to hold this but in the end I needed to sand it down so that the part would fit into the cavity easily.
Next in line is the on/off switch and the the rest (lights, battery and board)

You really need to work slowly so that all of the wires remained connected and fit into the bracelet.

The bracelet works fine but I'm already thinking about the next version. In this version I went for the smallest bracelet I could have that would fit all of the parts. In the next version I want to make a bigger, rounded off bracelet with more see through areas so that more of the bracelet would glow.