SparkFun Qwiic Visible Spectrum Emitter

It's easy to get used to the idea that RGB LEDs can emit millions of colors, and practically speaking, this is true enough. On the other hand, spectroscopically, they only emit three: Red, Green-ish, and Blue. Do you really care if the cyan and pink mood lighting in your gaming room is an illusion? Probably not. But sometimes there's no substitute for the real thing.

The Qwiic Visible Spectrum Emitter combines 9 discrete LEDs spanning the visible spectrum from 455 to 720nm. Each LED emits light with a narrow peak wavelength, with one exception made for the phosphor-based green LED in the middle of the spectrum. We compromised on green so that all of the LEDs would be in the same luminous intensity ballpark without breaking the bank. There are complicated physics reasons that pure green LEDs are not very efficient, if you're interested in learning more you can research the green gap.

This board is based loosely on the MultiSpecLED design by Ben Krasnow. Our design uses slightly less powerful LEDs and places them closer together. We've also made it Qwiic-compatible by designing around the LP55231 I²C LED controller. The idea was to create a broad-spectrum LED emitter for spectroscopy applications, but we suspect there are plenty of uses for this hardware from photography to photochemistry!

A USB-C port on the board allows you to connect a high-current 5V power supply for the LEDs and the exposed copper on the back is sized to accommodate our self-adhesive copper heatsink for applications where you might need active cooling. The LEDs can be run to about 80% PWM cycle without the need for an auxiliary heatsink or active cooling, but any higher than that and the board will warm up FAST.

Example Arduino code for controlling the Qwiic Visible Spectrum Emitter can be found in the SparkFun LP55231 Arduino Library!

Features:

• USB-C Connector for LED Power
  • 2x Qwiic Connection Ports
  • I²C Address: Default 0x35 (2-bit selectable)
  • 9 Discrete Single-color LEDs at the following wavelengths:
    • 455nm
    • 475nm
    • 500nm
    • 525nm
    • 540nm
    • 590nm
    • 615nm
    • 660nm
    • 730nm

Documents:

• Schematic
• Eagle Files
• Datasheets
  • LP55231 Programmable LED Driver
  • AL8860 Buck LED Driver
  • Cree J-Series LEDs
• LP55231 Arduino Library
• GitHub Hardware Repo