Reid Sox-Harris' Metamer SAO Gives Your Badge "RRAYLLGTTBB+UV+WWCWBWDW" LED Mixing Powers

Student and maker Reid Sox-Harris has built a Simple Add-On for badge owners who like a bit of color-mixing — but his Metamer SAO goes quite some way beyond red, green, and blue, to deliver what he describes as "RRAYLLGTTBB+UV+WWCWBWDW" mixing.

"A[n] SAO with all the LEDs to explain how metamerism works," Sox-Harris explains of his creation. "Instead of simple RGB color mixing, this thing can mix-n-match 16 unique spectra to make that perfect color you've been looking for. [It has] 12 unique wavelengths of LED + 4 temperatures of white [and] includes a really cool 496nm LED which is a color coming from an LED you've probably never seen before."

The concept behind the badge is, as Sox-Harris says, metamerism — matching colours of different spectral power distributions based on their perception, creating metameric matches that aren't a true match but look close enough to the human eye. "I do a fair bit of theatrical lighting, where color is a significant part of any design," Sox-Harris explains of his thinking behind the project.

"More LEDs gives a smoother gamut, better representative of what a tungsten source with filters might output. For example, ETC's new top-of-the-line LED fixtures uses 8 LEDs including an exciting new deep red for better skin tones. It's with that in mind that I designed this board: I wanted to demonstrate all the different ways LEDs could work together to create light, and how our eyes play tricks on us all the time!"

The result is a badge add-on that has 16 individual LEDs, every one of which covers a different wavelength — ranging from 456nm ultraviolet through to 640nm deep red, plus four different temperatures of white from 3,000 Kelvin warm white up to 11,000 Kelvin daylight. They're all connected to a Texas Instruments LP5018 LED driver, which is controlled via the badge's I2C bus. The idea: the ability to mix colors to find your own metameric matches, though at the moment Sox-Harris admits it's limited to "turning on and looking pretty."

After proving the concept with an initial design, Sox-Harris is now working on a second revision — which introduces a standalone mode, driven by a low-cost Puya PY32 as per Jay Carlson's recommendation. "[It] will be programmed to initialize the LED driver on power-up so that the SAO will actually display something, even on a default badge without custom firmware," Sox-Harris explains. "Plus, down the line I can perhaps offload animations and such to this MCU instead of doing it on the badge itself."

More information on the project's origins is available on Sox-Harris' website, with schematics, fabrication files, and source code on GitHub under the permissive MIT license. Additional details on the second-generation version can be found on Hackaday.io.