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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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