GEMMA Hoop Earrings – NeoPixel Ring Pendant

GEMMA jewelry! The bitty board fits perfectly in the center of a NeoPixel ring for flashy hoop earrings or a charming pendant. Read on to build your own!

Before you get started, follow the Introducing GEMMA guide or Introducing Gemma M0 guide.

Tools & Supplies

Bill of materials (for one pendant– double this for a pair of earrings):

  • Gemma M0 or Original Gemma
  • NeoPixel ring
  • tiny lipoly battery with charger
  • pendant hanger or ear wires/jump rings
  • stranded wire
  • clear thread
  • double stick tape
  • E6000 adhesive (if using glue-on pendant hanger)
  • soldering iron and solder
  • multimeter
  • scissors
  • wire strippers
  • pliers
  • flush snips
  • tweezers
  • helping third hand tool

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Circuit Diagram

The NeoPixel ring’s Data In pin connects to D0 on GEMMA, GND to Gnd, and Vcc to Vout.

Solder Components

Solder stranded wires to three spots on the NeoPixel ring according to the circuit diagram: power, ground, and data input.

Arrange GEMMA in the center of the ring, holding everything in place with a pair of helping hands.

Cut to length and strip the ends of the wires in order to connect to GND, Vout, and D0~ on GEMMA (referencing the circuit diagram). Tweezers can help get tiny wires in position.

Flip the assembly over and solder the wires to the back of the GEMMA pads. Be careful not to fill in the hold with solder, so that you can still thread a needle through it later.

Arduino Code

If this is your first time using GEMMA, work through the Introducing GEMMA guide first; you need to customize some settings in the Arduino IDE. Once you have it up and running (test the ‘blink’ sketch), then follow the instructions on the following page for installing the NeoPixel library:

NeoPixel Überguide: Arduino Library Installation

Plug in your circuit and load up the sketch below:

// Low power NeoPixel earrings example.  Makes a nice blinky display
 // with just a few LEDs on at any time…uses MUCH less juice than
 // rainbow display!
 define PIN       0
 define NUM_LEDS 16
 Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUM_LEDS, PIN);
 uint8_t  mode   = 0,        // Current animation effect
          offset = 0;        // Position of spinner animation
 uint32_t color  = 0xFF8000; // Starting color = amber
 uint32_t prevTime;          // Time of last animation mode switch
 void setup() {
   pixels.setBrightness(60); // ~1/3 brightness
   prevTime = millis();      // Starting time
 void loop() {
   uint8_t  i;
   uint32_t t;
 switch(mode) {
 case 0: // Random sparkles - just one LED on at a time!
     i = random(NUM_LEDS);           // Choose a random pixel
     pixels.setPixelColor(i, color); // Set it to current color;                  // Refresh LED states
     // Set same pixel to "off" color now but DON'T refresh…
     // it stays on for now…both this and the next random
     // pixel will be refreshed on the next pass.
     pixels.setPixelColor(i, 0);
     delay(10);                      // 10 millisecond delay
 case 1: // Spinny wheel (4 LEDs on at a time)
     for(i=0; i<NUM_LEDS; i++) {    // For each LED…
       uint32_t c = 0;              // Assume pixel will be "off" color
       if(((offset + i) & 7) < 2) { // For each 8 pixels, 2 will be…
         c = color;                 // …assigned the current color
       pixels.setPixelColor(i, c);  // Set color of pixel 'i'
     };                 // Refresh LED states
     delay(50);                     // 50 millisecond delay
     offset++;                      // Shift animation by 1 pixel on next frame
 // More animation modes could be added here!
 t = millis();                    // Current time in milliseconds
   if((t - prevTime) > 8000) {      // Every 8 seconds…
     mode++;                        // Advance to next animation mode
     if(mode > 1) {                 // End of modes?
       mode = 0;                    // Start over from beginning
       color >>= 8;                 // And change color
       if(!color) color = 0xFF8000; // preiodically reset to amber
     pixels.clear();                // Set all pixels to 'off' state
     prevTime = t;                  // Record the time of the last mode change

Affix Jewelry Findings

You shouldn’t rely solely on the wires to hold GEMMA in place. Secure it in four spots with clear thread– we’re using purple so you can see it better.

Thread a needle and pass it through a hole on GEMMA.

Tie the thread in a knot around the NeoPixel ring, aligning the thread between pixels. Do this in four spots around GEMMA to secure it in the center of the earring.

You can either glue a pendant hanger on the back with E6000 adhesive (hot glue is INSUFFICIENT), or attach an ear wire with a jump ring and two pairs of pliers.

A tiny lipoly battery can be affixed to the back with double-stick tape. Secure it further with more clear thread if desired.

Wear ’em!

Enjoy your precious jewels! Each circuit weighs a measly 11.39 grams! Keep them out of the rain, and switch off when not in use.

The first version of the GEMMA board did not include a power switch — if using one of these, you’ll need to unplug the battery to switch the circuit off.

Originally posted on Adafruit

If you like this project, you may be interested in some of my others:

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