This is a tutorial on how to make LED Pixel Poi. I have implemented the project in 2019 and have worked up and documented it in 2023 to make it available to anyone who is interested.

Todos:

• add images to the docu
• review of the docu

Each poi consists of a LED Strip and a microcontroller. When you switch on a poi, it searches for a wifi hotspot it knows. If it doesn't find one, it becomes a hotspot itself. In this way, the first poi you switch on becomes the master and all others connect to it as Slaves.The master also starts a web server that provides the user interface.

You can now connect to this hotspot with a smartphone, tablet or computer and open the user interface (UI) in the web browser. The UI is connected to the web server via websocket and so are all the slaves.

Images flashed to the Controller can selected or played in different auto mode speeds.

• turn on the master
• turn on all poi
• connect smartphone or tablet to wifi SSID: bitpixelpoi_*
  • (* is the MacAdress of the device)
  • Password: 1234567890
• open UI in Webbrowser: http://42.42.42.42
  • use the buttons to controll the poi
• Enjoy!

• Run the ImagePreprocessing
• copy the output file to TheSketch
• Use the resources in TheSketch to flash your ESPs
• wire your components and assemble your poi

for one Poi:

• 1 Microcontroller: ESP8266 Wemos D1 mini
• 1 Battery: 18650 battery with integrated protection circuit
• 1 Batteryholder
• 1 Led Strip: SK9822 LED Strip - 144 LED/m - One Meter - IP67
• yes, exactly, that is indeed already the whole technology

The ESP8622 is cheap, fast and has built in Wifi. I used a Wemos D1 board at first, as I had a few of them anyway. The only limitation was the somewhat small memory of 4MB, so I tried the Wemos D1 mini Pro with 16MB. Both work equally well.

To be able to flash the Wemos D1 mini Pro I had to install CP210x Windows Drivers: https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers?tab=downloads

I use a SK9822 led strip with separate clock and data line (4 wires in total). In comparison to the cheaper ws2812b and others with 3 wires the refresh rate ist much higher and this is what we need in this case. Adafruit Dotstar, APA102 are other with separate clock line.

144 Led/m was the most dense I found.

I recommend using the IP65 version (waterproof) beyause they have a soft silicone coating which makes them very impact resistant.

More Infos about Led Strips:

• https://www.derunledlights.com/de/the-difference-between-addressable-rgb-led-strip-ws2811-ws2812b-ws2813-ws2815-sk6812-sk9822/
• https://hackaday.io/project/162435-board-for-modular-led-wearables/log/158183-apa102-sk9822-and-dotstar-led-strips
• http://www.technoblogy.com/show?3SO4
• https://quinled.info/2019/01/21/ip20-vs-ip65-vs-ip67-waterproof/

• Battery to 5V and GND
• LedStrip to 5V and GND
• CLOCK_PIN D5
• DATA_PIN D7

The core consists of a wooden stick (beech, 8mm x 54cm) to which the LED strips are glued. At the upper end, a battery holder with a perforated metal band is attached as an extension of the rod. The hand straps are attached to this with key rings. The controller is glued to the battery holder. For better reflection, the wooden stick is wrapped with silver adhesive tape and the LED strips are glued to it. Everything is held together by transparent heat-shrink tubing.

Material list: (in addition to the hardware from above and a soldering iron to connect the harware)

• Wooden stick
• metal perforated tape
• transparent heat shrink tubing
• Hot glue
• Screws
• Key rings
• Hand loops
• neoprene velcro cable conduit
• soldering equipment

Batteryholders with springs, plastic wedges to disconnect thee battery or to fixate ist. On impact the controlle sometimes is reset. If it was the Master all connections are lost. To avoid this I sometimes use a third Cip as a non-poi master.

Batteries with soldered plugs may be more robust, just unplug to turn off.

Aruino IDE, PlatformIO

In the Sketch you can switch from 4 wire ones to 3 wire ones by changing the comments:

// #define USE_DOTSTAR 1
#define USE_NEOPIXEL 1

https://github.com/FastLED/FastLED/wiki/Chipset-reference

1. Install nodejs and npm
2. Clone this repo
3. put images into ImagePreprocessing/in or use the samples
4. run ImagePreprocessing/index.js
   • cd ImagePreprocessingauto
   • node index
   • all images in ImagePreprocessing/in are processed
   • ImagePreprocessing/mypixels.h is generated and overwritten

• read images
• resize to 72 px heigh
• read pixels
  • create palette
  • write numeric array
• optimize gamma
• create html with css an js for ui
• write all to mypixels.h

src/main.cpp ist the entrypoint, also to read the code.

The included file mypixels.h contains the images as numbers and the HTML UI as String.This file is the output of the image preprocessing.

Needed Libraries:

• ArduinoJson
• arduinoWebSockets
• ESP Async WebServer
• FastLED