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Tiny Snowflake

LEDs blink randomly on this snowflake-shaped PCB

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The Tiny Snowflake is a PCB shaped like a snow flake with 19 LEDs. The LEDS are independently controlled by an ATTINY 13 using charlieplexing. Code is uploaded to the device with AVR dude using a Bus Pirate, a AVRisp mk II or similar. It is not Arduino compatible.

These snowflakes were originally designed for my mother, who is a public school teacher. She loves to decorate her classroom for each holiday, but is not allowed to have religion-specific decorations. Snowflakes are festive, but not religious so it is ok to have them at school.

The best part of the project was that over thanksgiving break I got to teach all my nieces and nephews how to solder these together and program them. I woke up late one morning to find 11 soldered by the kids. Now they all love tinkering in electronics.

Tiny Snowflake

Introduction

The Tiny Snowflake is a PCB shaped like a snow flake with 19 LEDs. The LEDS are independently controlled by an ATTINY 13 using charlieplexing. Code is uploaded to the device with AVR dude using a Bus Pirate, a AVRisp mk II or similar. It is not Arduino compatible.

Theory

Soldering The Snowflake

Materials

  • 5 110 Ohm resistors
  • 1 0.1 uF capacitor
  • 19 LEDs
  • 1 ATtiny13A
  • 5v power source (USB, batteries, etc.)

To solder the snowflake follow these steps:

Front of SnowflakeBack of Snowflake

  1. Solder on all 19 LEDs paying attention to the LED orientation on the silkscreen.
    • The center LED is the only one that is not paired so it is very important that it is in the correct orientation. For the rest it is ok to have them all inverse (or just the spokes or just the ring) because this is charlieplexed so these 18 LEDs are in groups of 9 opposing pairs.
  2. Solder the capacitor onto the PCB.
  3. Solder the ATtiny13A onto the PCB.
  4. Solder the Resistors onto the PCB.
  5. Solder the power cable onto the PCB.
  6. (Optional) Chain them together by soldering cables onto each other.

Uploading Code

Whats Inside the PCB?

schmatic

This is the schematic of the PCB, showing how all the components are connected.

PCB

This is a transparent view of the PCB. Green lines are wires on one side and red lines are wires on the other side of the PCB. The text that will be printed on the board is in magenta on one side and teal on the other. The yellow line is the edge of the board. The gold circles are drilled through the board and have copper on both sides.

How I Made the Gerbers

  • 5 × 110 ohm 0603 resistor
  • 1 × .1 uF 0603 capacitor
  • 19 × 0603 LEDs
  • 1 × ATTiny 13 A-SS
  • 1 × 3.3-5V power source (USB, Batteries etc.)

  • 1
    Solder on all 19 LEDS paying attention to the LED orientation on the silkscreen.
    • The center LED is the only one that is not paired so it is very important that it is in the correct orientation. For the rest it is ok to have them all inverse (or just the spokes or just the ring) because this is charlieplexed so these 18 LEDs are in groups of 9 opposing pairs.
  • 2
    Solder the capacitor onto the PCB.
  • 3
    Solder the ATtiny13A onto the PCB.

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Discussions

John Oliva wrote 12/13/2018 at 20:21 point

Nice work.  I especially liked your video describing Charlieplexing.

  Are you sure? yes | no

hammeshacks wrote 12/09/2018 at 10:12 point

Actively maintained version of this project can be found at hammeshacks.com

  Are you sure? yes | no

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