What is it?

Earrings with LED's to light up any occasion. The different patterns are controlled by an ATtiny84a and programmed with the Arduino IDE. These earrings are powered by a CR1225 coin cell battery, and will last at least a day, and up to 2 weeks (depending on the pattern and the color (voltage forwarding) of the LED). A button on the back of the earring can be used to select different patterns, or to turn off the device.

Why did you make it?

Challenged myself to use the ATtiny84a in something special. The small foot print of the micro-controller allowed using this in an earring. I wanted a very simple design, and by using the coin cell battery, I was able to run the LED's without current resistors (current of the coin cell is low enough). Two capacitors are placed close to the VCC pin of the ATtiny84a to make sure the voltage stays consistent while the LED's are flashing. I also wanted to experiment with using different layers on the PCB. The 'silver' on the earring is accomplished by removing the soldermask in that area.

What makes it special?

The earrings are entirely assembled by hand. I use a stencil and reflow oven to install the components on the font, the back is done with a soldering iron. Programming is done with the Arduino IDE. To conserve energy, the ATtiny84a is in sleep mode, 99.9% of the time. It only wakes up to determine which LED should be turned on or off before entering sleep mode again.

Extreme close-up of the ATtiny84a microcontroller used to control the LED's (3x3mm foot print!)