Human Centric Lighting (HCL): What Is It and How Does It Work

Humans need natural light. Learn how Human Centric Lighting is used to adjust indoor lighting to align with the sun for increased health and happiness.

By Jeremy Cook

The Organic Effects of Light 

Throughout most of the history of humankind, humans spent much of their waking hours outdoors. The sun guided when to sleep and wake, rivaled only by the orange/red-tinted firelight that helped us function into the night. As such, human bodies are naturally wired to respond to the rhythm of the sun. We recognize the blue hues of the middle of the day via our eyes as a time to be active and the yellow-red sunset as a time to relax in preparation for sleep. However, with the constant stream of indoor lighting in modern life, we've lost much of this attunement. Human Centric Lighting (HCL) aims to restore this balance.

Challenges of Today’s Light Sources 

It was around 150 years ago that our outdoor-centric existence began to shift. The invention of the electric lightbulb that could provide instant illumination was the first significant driver towards "sun independence." One may also argue that we were further separated from the sun's glowing cues by the advent of air conditioning, which allowed for cooling in interior offices without windows. This also motivated humans to stay indoors and away from the oppressive (though biologically informative) sun.

Fast forward to today, and the addition of ever-present glowing screens further exacerbates light confusion. Replacing the sun with a haphazard array of light sources has jumbled the natural lighting cues of our ancestors. You likely wake to a harsh light with a color hue that seemed soothing the night before but doesn't evoke the full daylight corresponding to its intensity. Before bed, you may find yourself staring at a computer screen or tablet that emits "mid-day" blue light hues. It's a source of potential confusion on both ends of the spectrum for your internal circadian clock, which regulates much of the body's function.

How Does Human Centric LED Lighting Work?

As a potentially healthier alternative, new technological developments have enabled cost-effective lighting that can both be dimmed as needed, and programmed to change hues to coordinate with our fiery orbital overlord. This mimicry of the sun's pattern is the crux of human centric lighting.
To accomplish this, dual-LED white lighting setups can produce the correct light color by combining different intensities of "daylight" and "warm" lighting sources into one consistent hue and expressed in units of degrees Kelvin. RGB (red, green, blue) and RGBW (red, green, blue, white) LEDs can be fused for even more versatility. In addition, with inexpensive IoT capabilities, often using ESPRESSIF ESPx chips, proper lighting can happen without your direct input, just like the sun's natural constant cycle rise/set cycle.

HCL Applications

On a macro level, the concept of HCL may mean that home lighting designers seek out systems of tunable lighting for optimal use and comfort. Consumers would be wise to consider such factors when purchasing new bulbs. Factories would also want to be aware of lighting temperatures to evoke productivity, simulating daylight hours even during night operations. Workplaces may also consider keying lights to follow a pattern corresponding to shift changes and break times for enhanced worker satisfaction.

On a personal level, each of us should at least be aware of what color temperatures are being used around us and consider our screen usage at night. When designing electronics and electrical components, engineers would be wise to be aware of HCL factors to allow hue-conscious consumers to choose their preferred lighting solution.



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