The magic of Neo-pixels

After writing this title, I realized there is a post from Adafruit with the same title. And that is for a good reason in my opinion!

Neo-pixels are not just a strip of LEDs in series! They are individually addressable through a single data wire and this makes them very special in terms of what you can do with them! Each one of the LEDs has an integrated circuit (called WS2812). I really suggest this part again from adafruit if you are interested!

Bottom line is that there are 3 bytes of data for each RGB LED, each one representing how much of each R/G/B is going to be in each LED. 1 byte is an integer from 1 to 255 and this is your resolution for each color as well. So the awesome thing is the whole strip operates like a huge shift register!

The way that the system works is very simple: after you have fed a new value to the data wire, it is staged for refreshing in the first LED (closer to the micro-controller). When you feed a second set of 24bits, it goes to the second LED in the chain and so on. Finally, by setting the data wire “low” for more than 50 microseconds the colors are refreshed for the whole strip.

Construction/inspiration

I was mostly inspired (and educated about the project) by Great Scott that did the same with an arduino. I used directly an ESP32 because I wanted to be able to refresh the screen wirelessly. I also have a single arduino for experimentation and I wanted this to be a permanent installation in my room.

Components

  • The LED strip (ordered from Ali-express)
  • a strong power supply (4 amps). The LEDs draw quite some current when they are fully lit.
  • Beach wood for support
  • a thick while acrylic sheet (I found that on the street actually - that was nice since it’s not cheap!)
  • carton (that is to separate the LEDs so they have a “pixel-like” definition when lit.
  • ESP32 to control the LEDs and interface with Wifi.

Tips:

you might have to put some supply in parallel - the LEDs have quite some resistance and LEDs closer to the end of long chains may end up with lower current and inaccurate/faded colors. Maybe have a look at this video to better understand what I’m talking about.

In my github repo you can find a version of the code I used plus a python script I made to control it.

The way the remote control works, is that I send REST requests containing serially encoded in the text the values for all the LEDs. If you think what I should have done to do this first it will be easier to read my code. In any case, drop me an email at mylonas.charilaos@gmail.com in case you are interested in adapting it - I’d be happy to help!

Here are some fotos of the construction. I had to clamp the board to sth so I can saw it: construction 1 construction 2

The matrix after I have split the strip, glued it to the wood and before I soldered all the connections for the power and data. construction 3

Constructing the frame: construction 3

A video of the matrix running a default script with an arduino before I constructed the carton grid to give it the pixel look:

Finally, I made a short python script that translates ASCII art to color data for the matrix! Here is an example: a smiley face

In the github code upload you will also find the ASCII codes for that.

H.