Rainbow Strip

thingiverse

The purpose of this project is to develop an attention-grabbing, waterproof, animated rainbow light strip that can be shamelessly exploited for financial gain during Pride celebrations. Built around an Adafruit Neopixel strip, an Arduino nano, and any standard 5-volt mobile power bank, this device allows the proud individual to dance for hours on end without interruption. At its core is the Arduino sketch that generates a rainbow corresponding to the number of LEDs in your WS2011b (or similar) light strip. The main feature of this project is an algorithm that uses trigonometry to create a color wheel where the circumference equals the number of LEDs in the strip. Although it's not 100% exact, the relationship between PWM level and LED brightness is far from linear. As a result, you don't get a smooth blend between colors, but the major colors show through clearly. The formula for creating the color wheel is essentially as follows: x = 2 * Pi / (LED# +1) (where LED# is the address of the current LED in the strip). Red=cos(x) * Maximum_Power_Level Green=cos(x + 2*Pi/3) * Maximum_Power_Level Blue=cos(x + 4*Pi/3) * Maximum_Power_Level. In other words, the Red, Green, and Blue values are offset from each other by 120 degrees. The second algorithm in the sketch simply shifts whatever is on the strip to the next pixel. This sketch relies on the NeoPixel library. Kudos to Adafruit for their amazing hardware, libraries, and community support. To house the Arduino nano and wires, I used Microsoft 3D paint to create a hollow cylinder. While it's not the most ergonomic model and the holes could be larger to fit all the wires, I'm more than happy to hear recommendations for a more suitable enclosure. The wiring diagram is exactly the same as what Adafruit recommends for connection of its NeoPixel strip - a 100uF capacitor and a 230 Ohm resistor.