Introduction: BLU - a Wearable Sensor/status Bracelet

Picture of BLU - a Wearable Sensor/status Bracelet

This project was undertaken as I was applying for Intel's "Make it Wearable" contest (

Trailer of that contest:


Although I did not win I decided to try to build my idea. While the idea is not so simple here it is summarized [also see video]: a wearable device that has embedded sensors to monitor your environment and give you feedback/information on certain parameters and most prominently the quality of air and water.

This is only step one: designing a simple bracelet that displays the status of anything with embedded LEDs in a nice light diffusing 3D printed casing. Hopefully later down the road I'll be able to achieve the final goal as described in the BLU video.

Step 1: The Casing

Picture of The Casing

The original design is the white 3D printed bracelet - it was too fragile and turned out quite ugly...

The second try; a much simpler design worked quite well. Simple arcs with a hollow portion in the middle. There is the main body and the cover. The design is very solid, and diffuses the light. It may not look super classy - but it ain't too bad either!

Step 2: Light Diffusion

Picture of Light Diffusion

To have a nice and diffused light I utilized a few different tricks:

  1. I used Suguru ( A little dab of white suguru on each LED and the light was much "softer".
  2. I put a layer of white paper inside the walls of the bracelet and transparent (opaque) tape on the paper.

Step 3: The Electronics

Picture of The Electronics

The electronics are very simple:

- Arduino Gemma ( ) [although any mini Arduino will do!]

- Lithium cell battery

- 3 or more Neopixels (

And they all nicely fit into the casing!

For the battery, any battery should do... but I have a preference for lithium as they are small, hold a decent charge, are easy to get and have the ability to be recharged.

Step 4: The Code

Here is code I wrote for it. It's pretty strait-forward and simple.

  1. It uses the following Arduino library:
  2. For a lot of tutorials and further tips on Neo-pixels, this page is quite useful:



//requires library from

//arbitrary PIN for now

#define PIN 2

#define WAIT 20 //milliseconds off time between next color

#define SEQLEN 5 //memory of array = how many colors?

#define SEC 1000 //millis in a second

#define NUMPIXELS 10

#define PI 3.14159

// Parameter 1 = number of pixels in strip

// Parameter 2 = Arduino pin number (most are valid)

// Parameter 3 = pixel type flags, add together as needed:

// NEO_KHZ800 800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)

// NEO_KHZ400 400 KHz (classic 'v1' (not v2) FLORA pixels, WS2811 drivers)

// NEO_GRB Pixels are wired for GRB bitstream (most NeoPixel products)

// NEO_RGB Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)

Adafruit_NeoPixel light = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

//color sequence

//define each element using light.Color(R,G,B) function.

uint32_t WHITE = light.Color(255,255,255);

uint32_t RED = light.Color(255,0,0);

uint32_t GREEN = light.Color(0, 255,0);

uint32_t BLUE = light.Color(0,0,255);

uint32_t YELLOW = light.Color(255,215,0);

uint32_t colors[SEQLEN] = {


//how long each color.

uint32_t colortime[SEQLEN] = {

10*SEC, 6*SEC, 6*SEC, 6*SEC, 6*SEC};

unsigned long t0 = 0;

void setup(){


/* colors[0] = WHITE;

colors[1] = RED;

colors[2] = YELLOW;

colors[3] = GREEN;

colors[4] = BLUE;




void loop(){

for(int bulb = 0; bulb < SEQLEN; ++bulb){

Serial.println("Setting new bulb");




t0 = millis();


unsigned long t = millis()-t0;

while(colortime[bulb] - t*1. > 0){


for(int pixel = 0; pixel < NUMPIXELS; ++pixel){

light.setPixelColor(pixel, colors[bulb] );



t = millis()-t0;

Serial.println(colortime[bulb] - t*1.);;


// delay(colortime[bulb]);

#if WAIT

for(int pixel = 0; pixel < NUMPIXELS; ++pixel){







Step 5: Results & Further Additions

Later down the road as time and funds become available I'm going to add Bluetooth (perhaps with one of these?

And then comes the tricky part: the sensors! But in the mean time it looks wicked cool :) ! [see video]

Tips and ideas are welcome!


supercapacitor (author)2014-07-18

This is a really good idea. Imagine if the tech was made affordable to people in developing areas...

lol yes

Wow, this is so pretty!

Thanks! :)

gada888 (author)2015-04-28

The code is a bit strange,GEMMA utilize the juice of an attiny85,while attiny85 doesn't support serial the result is it won't complie.

LostNeutrino (author)2014-07-16

Hi Sam!

"... then comes the tricky part: the sensors!" - I haven't investigated which sensors to make/purchase and integrate yet - but I'll update the post as I do it in the future.

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