Falling Block Earrings

Light-up earrings that play a tiny falling-block game on a 6×10 grid of 1 mm RGB LEDs, powered by a coin-size battery.

Started

  1. Idea
  2. Schematic
  3. Design review
  4. Board layout
  5. Prototype v1
  6. Prototype v2
  7. Finished

A pair of earrings, each with a 6 × 10 grid of tiny RGB LEDs that play a pre-programmed falling-block animation. Each one has to fit a microcontroller, 60 LEDs and a battery into something light enough to wear.

The plan

  • Brain: ATtiny1616 microcontroller, programmed through its 3-pin UPDI header.
  • Display: 60 × XL-1010RGBC-WS2812B addressable LEDs (1 mm × 1 mm each), in a 6 × 10 grid.
  • Power: an LIR1220 rechargeable coin cell, with P-channel MOSFETs (DMP2160) switching power to the LED rows so unused rows draw nothing.

Iteration log

v0: Schematic (done)

Drawn in Altium. The first version used a PCAL6416A I/O expander to drive the MOSFET gates.

v0.5: Design review (now)

Reviewing the schematic before layout turned up a few problems:

  • The battery is too small. An LIR1220 holds about 9 mAh and is rated for roughly 9 mA. Sixty WS2812-style LEDs can draw more than that just sitting idle.
  • The I/O expander can probably go. The ATtiny1616 has enough pins on its own, which saves a chip and a lot of routing.
  • Startup safety needs pull-up resistors, not capacitors, so the LEDs can’t all switch on at power-up.
  • Everything needs to shrink: QFN microcontroller, 0402 passives, and LEDs on the front with the rest on the back.
  • Still to add: a charger and low-battery shutdown.

Next step: pick the power and LED approach, then redraw the schematic.

Parts list

PartNumberQty per earringNotes
MicrocontrollerATtiny16161Moving from SOIC-20 to QFN
RGB LEDXL-1010RGBC-WS2812B601 × 1 mm
Row switch MOSFETDMP2160UFDBQ-75P-channel
BatteryLIR12201Under review: probably too small

Files

Schematic PDF and firmware will go here once the design is settled.