Background Research

To build our window, we have had to do research on a number of topics. Some are more theoretical and involve scholarly articles, while others are more practical and involve commercial product descriptions and how-to guides. Here are brief summaries of our research on each topic along with our sources.

Effect of Light on Circadian Rhythms

Humans have circadian rhythms that guide their daily routine, and sunlight plays an important role in regulating them, as the human body keeps track of its biological rhythm with exposure to light and darkness [1]. Dark and windowless rooms can have an adverse effect on health, as can artificial lights that do not accurately replicate natural light. Most lights used in buildings are fluorescent and have erratic emission spectra with spikes in wavelengths due to the emission spectra of the individual gasses used in the bulbs. These lights also constantly emit blue light, which is the wavelength of light that resets our circadian rhythms with the greatest efficiency [2]. This is unlike natural sunlight, which has a smooth emission spectrum curve that shifts over the course of the day. Around noon, there is a high intensity of blue light, which increases the production of serotonin in the body, increasing alertness and cognition. In the evening, there is little blue light, and instead red and orange light is more intense, which enhances the production of melatonin [3]. This lack of natural light can lead to eye fatigue, sleep problems, and an overall disruption of circadian rhythms. LED lights have much smoother spectrum curves that mimic natural sunlight more accurately.

Color Temperature and RGB LEDs

Color temperature is a way of representing the color of light, measured in degrees Kelvin, which is based on the temperature of blackbody radiation coming from the light source [4]. Data on the effects of light on circadian rhythms is often presented in terms of color temperature [3]. However, for the purpose of LED daylight-matching, the data needs to be in RGB values. Luckily, the concept of color temperature is commonly found in photography, and photographers need to be able to color correct their photographs [5]. Some photographers have developed algorithms to convert color temperature to RGB [5] [6]. These algorithms can also be used to match LED colors to sunlight.

Arduino

To control our light, we are using an Arduino microcontroller, a small, basic computer that can connect to and control electronic devices [7]. The Arduino has its own language based off C/C++, including its own function libraries, and its own software development environment [7]. It also has many unofficial community-made libraries, including libraries to use an RTC and keep track of time [8] [9] [10]. The Arduino’s breadboard also has the ability to control electrical devices, including changing the colors of RGB LEDs using pulse-width modulated voltage output [11]. The ability to keep track of time and control the color of LEDs makes the Arduino useful as the controller of our window.


LED Diffusing Plate

The common method for creating commercial daylight-matching windows is using a diffusing plate to create a natural glow [12]. The material we are using for our window pane is a ULED diffusing plate made with nanoparticles for the purpose of sharpening the image of light on LED televisions; this also makes it function as a diffuser for any sort of LED backlighting [13]. This diffusing plate will take what would ordinarily appear as a bunch of individual LEDs and combine them into one single glowing panel, creating the same sort of ambient light as ordinary daylight.

References

[1] J. Duffy and C. Czeisler, "Effect of Light on Human Circadian Physiology", Sleep Medicine Clinics, vol. 4, no. 2, pp. 165-177, 2009. Available: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717723/. [Accessed: 06- May- 2016].


[2] D. Holzman, "What's in a Color? The Unique Human Health Effects of Blue Light", Environ Health Perspect, vol. 118, no. 1, pp. A22-A27, 2010. Available: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/. [Accessed: 06- May- 2016].


[3] "BAU Architecture", Bauarchitecture.com, 2016. [Online]. Available: http://www.bauarchitecture.com/research.daylightleds.shtml. [Accessed: 06- May- 2016].


[4] M. Charity, "Black Body Radiation Data", Vendian.org, 2016. [Online]. Available: http://www.vendian.org/mncharity/dir3/blackbody/UnstableURLs/bbr_color.html. [Accessed: 06- May- 2016].


[5] T. Helland, "How to Convert Temperature (K) to RGB: Algorithm and Sample Code", Tanner Helland (dot) com, 2012. [Online]. Available: http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/. [Accessed: 06- May- 2016].


[6] N. Bartlett, "Color Temperature conversion of Homestar.io – ZombiePrototypes", Zombieprototypes.com, 2015. [Online]. Available: http://www.zombieprototypes.com/?p=210. [Accessed: 06- May- 2016].


[7] "Arduino - Introduction", Arduino.cc, 2016. [Online]. Available: https://www.arduino.cc/en/Guide/Introduction. [Accessed: 06- May- 2016].


[8] "Arduino Playground - Time", Playground.arduino.cc, 2016. [Online]. Available: http://playground.arduino.cc/Code/Time. [Accessed: 06- May- 2016].


[9] "Time Library, Timekeeping and Time/Date Manipulation on Teensy", Pjrc.com, 2016. [Online]. Available: http://www.pjrc.com/teensy/td_libs_Time.html. [Accessed: 06- May- 2016].


[10] "DS1307RTC Library, For Accessing Real Time Clock (RTC) Chips", Pjrc.com, 2016. [Online]. Available: http://www.pjrc.com/teensy/td_libs_DS1307RTC.html. [Accessed: 06- May- 2016].


[11] "Arduino Playground - TimerPWMCheatsheet", Playground.arduino.cc, 2016. [Online]. Available: http://playground.arduino.cc/Main/TimerPWMCheatsheet. [Accessed: 06- May- 2016].


[12] "Adaptive LED Lights with Smart Color-changing Technology", Walalight, 2016. [Online]. Available: http://www.walalight.com/products/walalights/. [Accessed: 06- May- 2016].


[13] "Hisense ULED TV", Hisense-usa.com, 2016. [Online]. Available: https://hisense-usa.com/uled/. [Accessed: 06- May- 2016].