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We bought a lighted Christmas tree from Amazon that had RGB lights. It lasted a season before dying. This year I decided to make a Christmas tree topper for my wife as Christmas is her favorite holiday. It involved designing a small circuit board for the LEDs, reflowing the LEDs in a toaster oven, designing and printing the topper, writing code for an ESP32 to drive the LEDs, and creating a small website to easily control the lighted topper.


To start with, I wanted to use some new LEDs I hadn’t used before. The APA102 LEDs (also known as Dotstar) are a little more forgiving on timing than the standard Neopixel LED. I purchased the LEDs and a breakout board from a supplier. Unfortunately I didn’t like the layout of the board as it had only one power and one ground connection which was not conducive to multiple LEDs as I’d have to share connections. I designed my own board with 4 connections on each side so I had power and ground in and power and ground out as well as data and clock in and out. The boards pins were on 2mm spacing so I could use headers as an easy way to wire in and out. Note there are pads for a capacitor on the top or bottom if needed for noise immunity.


For wiring, a barrel jack is the connection for the 5V power from a wall wart. That goes into technically the last LED in the chain and it is daisy-chained through the other LEDs all the way to LED 0 which has four connections to the ESP32, 5V power, ground, MOSI, and SCK. The power is switched so it can be turned off during USB connection to prevent the wall wart from feeding my computer’s USB port with 5V. Each LED has 8 connections, the 4 on the left are Power, Data In, Clock In, Ground, and on the right Power, Data Out, Clock Out, and Ground. Power and ground are pass thru while the data and clocks pass through the LED which acts as a shift register. I used 2mm headers to connect each LED to each other where I could, and at the ends I used ribbon cable to return to the center. If you look at the LED at the center, that is LED 0, then count outwards and counter clockwise for the data path.


3D Print files, code, and more instructions and photos located here:

http://blog.colecago.com/?p=807


Bill of materials used in this project

APA102
1
Jan 27,2020
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    VOTING 6 votes
    • jordanyte from UNITED STATES OF AMERICA
      Ben Jordan is a board level electronics and embedded systems design engineer. Always an avid tinkerer, Ben started with his first soldering iron at the age of 8, designing and etching his own PCBs soon after. Ben is an expert in EDA with Altium, Protel, CircuitMaker and CircuitStudio and has a Bachelor of Engineering (CompSys) Hon I. from the University of Southern Queensland, Australia. He is an IPC-CID+ certified PCB designer, and makes training videos for Altium Academy.
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    • Emre KONCA from TURKEY
      I'm system engineer. https://www.youtube.com/ArduinoHaberTV
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    • Jorge from SPAIN
      maker. I like to build things, to understand how things work. Co-founder of Ripolab Hacklab, a non-profit organization to explain the culture maker
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    • www.cursoderobotica.com
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    • Jiri Praus from CZECH REPUBLIC, THE
      I am an artist. I design electronics and brass wire sculptures. www.jiripraus.cz
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    • Inventor of TV-B-Gone, a keychain that turns off TVs in public places. Co-founder of 3ware, a successful Silicon Valley startup in the 1990s. Pioneer of Virtual Reality in the 1980s. Author and teacher. I go around the world giving talks and workshops. Promoter of hackerspaces, open source hardware. Mentor for others wherever I goes. Co-founder of Noisebridge hackerspace in San Francisco. President and CEO of Cornfield Electronics. http://en.wikipedia.org/wiki/Mitch_Altman
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