A Christmas tree geek with ShiftPWM

The year-end holidays approaching I wanted to find an idea Deco 100% Geek. With My wife who makes many DIY, We therefore started in the realization of a mini tree.

The idea was fairly simple : use of RGB LEDs to decorate a mini tree. Unfortunately the mounting could not do with a Raspberry Pi without going through a DAC (Digital to Analog Converter). The wiringPi library can emulate outputs analog but with a frequency that will be insufficient and will block the CPU to 100%.

Here is the list of the equipment :

  • An Arduino Uno with an AtMega328
  • 4 shift register 74HC595, each piece for controlling 8 outputs so not quite 3 LED …
  • 9 RGB LED with common cathode
  • 27 resistance between 220Ω and 270Ω (one by the LED pin)
  • A good dose of son !

I simply then applied the connections offered by the ShiftPWM library that will make it possible to control very simply the shift registers and the connected LEDs behind.

I have not used transistor or regulator, everything is connected next to the Arduino.

Side programme, I have there also used the example of the ShiftPWM library by specifying the number of shift registers and removing each LED test loops. I kept only the party generating a rainbow.

Here is a video with the core program :

My wife then intervened to “Mount” FIR. The poor thing was not helped by my 40 cables connecting the LED all !

Here's the side mounting Arduino

P1120617 P1120618 P1120619

And the end result after a women's aid :


J’ai pas réussi à faire plus joli pour les câbles 🙁



All the tricks and the realization images are on this page at Blackconfetti.fr

Thanks to Elco for this library “Magic” 🙂

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