Cree LED Revolution Blog
Cree and LED lighting are starting a revolution
March 28th, 2012
Today’s guest blog post comes from Gary Trott, a product development innovator for Cree LED Lighting focused on developing solid state lighting products for general illumination. Gary holds numerous patents covering some of the most significant new product releases in the past ten years and has played an instrumental role in helping Cree develop some of its award-winning LED lighting products.
One of life’s more unpleasant chores is cleaning out dead bugs from light fixtures. If you’ve ever emptied a pile of dead flies and moths from a fixture, you know light fixtures of all types are notorious for attracting and collecting insects (see what I’m talking about below).
In fact, many companies carefully design fixtures to keep bugs out, and yet they always seem to find a way to get in!
I was involved in the team that commercialized the Cree LR6 LED downlight more than four years ago. During development, bug ingress prevention was NOT a design goal. However, I have noticed that the LR6 downlights installed above the door I walk through almost every day have ZERO bugs in it – after more than four years of installation! See pic below:
My curiosity piqued, I set out to try to understand why. I asked Marianne Shockley Cruz, Ph.D., with the University of Georgia Department of Entomology to summarize known research about insects and attraction to light. The result of this work is in the paper “Insect Vision: Ultraviolet, Color, and LED Light.”
Here are some of the key points:
Insects are Sensitive to UV Light
The research validates something most of us were taught about insects’ attraction to UV light by those purple bug zappers that vaporize bugs every few seconds on a summer night.
“Color sensitivity in the UV spectrum plays an important role in foraging, navigation, and mate selection in both flying and terrestrial invertebrate animals. This attraction to UV light has made insects a useful model for understanding visual sensitivity to UV light”
Cree LEDs emit little or no power in the UV spectrum. Incandescent, fluorescent, and metal halide sources emit a substantial amount of UV radiation, thus it is likely that bugs are less attracted to fixtures utilizing Cree LEDs.
In fact, the primary goal of the fluorescent tube is to generate UV radiation to excite phosphors. No wonder there is so much UV in its spectrum!
Insects are Attracted to Some Visible Wavelengths of Light
White light is a combination of many colors that our eyes perceive as white. You can see the variety of colors of the visual spectrum in rainbows. These colors are technically described by a spectral power distribution (SPD) which reports the relative intensity of each color in a light source. Each wavelength of light reported in nanometers is perceived as a specific color, and research has shown that insects have varying sensitivities to different colors of light in an SPD.
“In behavioral studies, Indian Meal Moths were most strongly attracted to UV (365 nm) and green (500 nm) lights, suggesting that the eyes are potentially dichromatic.”
The spectral power distribution of fluorescent and metal halide lamps exhibit significant intensity peaks in the green spectrum. The intensity is significantly higher than the emission of typical Cree LEDs.
Cowan and Gries (2009) tested the hypothesis that moths use wavelengths of visible blue/violet light as orientation cures that trigger phototactic responses. In a four choice lab experiment, blue light was more effective than green, orange, or red light. In subsequent experiments that tested LEDs emitting peak wavelengths in the blue/violet light range, 405 nm was significantly more effective than 435-, 450-, or 470-.
The output of Cree LEDs at the 405 nanometers wavelength is almost zero compared to a significant spike with fluorescent light (see reference chart below). These two studies offer additional possible reasons why bugs are less attracted to fixtures using Cree LEDs.
There is no definitive research that can explain why insects are not attracted to Cree LEDs. However, there are a number of findings suggesting many reasons why bugs may not be. The most powerful of all is that insects have UV receptors and their behavior is affected by UV light – and Cree LEDs emit almost no UV radiation.
My personal proof is found in the LR6 downlights I have observed without a single dead bug inside after four years.
Does anyone have any interesting experiences or insights about bugs and lighting they would like to share?