LeuchteLine (GlowLine)

A few months after creating the SlackCell Michi had the amazing idea of adding LEDs to a slackline which change color depending on the current tension of the line. This should have been a straight forward task as I'm using a Arduino Nano in the SlackCell. So connecting the data line of the WS2812 LEDs I had lying around for my 3d printer to the Arduino, supplying the LEDs with 5V and some minor tweaks in the code should have done the trick for a fast prototype. This was kind of true but sometimes life doesn't go according to plan.

Choosing the library

I started another LED project some time ago and used the NeoPixel library. I added some RGB-gamma-correction and a RGB-to-HSV converter. While trying to eliminate the library as the root of my problems I tested FastLED and found out that it can do all this and more. So I ended up using this library.

Supplying 5V

This should have been the easiest part. Plug in the LEDs in 5V and that's it. The only thing that seemed to work was my breadboard power supply. But I want to use the LeuchteLine outdoors and there are no power sockets. So I tried powerbanks which didn't work because I guess my 5 LEDs prototype didn't draw enough current. I also tried a Li-Ion cell with two different step up converters which didn't make it glow. In the end I used 300 LEDs (5 m) which worked fine with my powerbank.

Arduino

To cut a long story short most my problems where due to the Arduino not being able to control the LEDs while being powered by the inbuilt power supply (Li-Ion + step up). Furthermore the Nano only has 2kB RAM which is not enough for Bluetooth, OLED and 300 LEDs. So I removed the OLED because nobody will be interested in the actual tension in the line while letting it glow. For more LEDs I have to use another micro controller and communicate with the Nano over serial.

The code is simple right now. Saving min and max forces and mapping them to the color spectrum. As the spectrum starts and ends with red I map the values not to the full range but to 20 - 255 to have a distinction between min and max tension.

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maxForce = max(force, maxForce);
minForce = min(force, minForce);
hue = map(force, minForce, maxForce, 20, 255);
FastLED.showColor(CHSV(hue, 255, 100));

First test

I taped the LED strip with fixed tapes to my garden line. It was not the best idea because Sigma N is super stretchy and created some LED loops. Other than that the first real test on a line looked promising. This opens up so many possibilities for spectacular light shows while slacklining. I can't wait to be finally be back freestyling and glowing in the dark with my LeuchteLine.