Tunable white lighting: It must be digital (MAGAZINE)

June 2, 2017
Forward-thinking control system providers have the opportunity to drive progress, push the technology envelope, and set the standard for digital controls that help create dynamic, personalized environments in any space, explains Lutron's Craig Casey.

Forward-thinking control system providers have the opportunity to drive progress, push the technology envelope, and set the standard for digital controls that help create dynamic, personalized environments in any space, explains Lutron's CRAIG CASEY.

In just the last five years, LEDs have completely transformed the lighting landscape. Originally embraced as an energy-saving option for lighting retrofits and code compliance, lighting professionals and their customers often had to compromise - efficiency versus ambience. Not anymore. LED lighting offers a wide variety of advantages including excellent color rendering and superb dimming capability. Tunable white is the current hot topic, and digital control is essential for making the most of white tuning potential.

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White tuning research is still relatively new, but the evidence increasingly points to a wide variety of human-centric benefits, and potentially even health benefits, that can be realized through control of fixture color temperature. Specific, physiological benefits are still unclear, but there is no question about the aesthetic value and flexibility white tuning provides. Lighting designers and specifiers are looking for a simple way to use this new technology to better meet their customers' needs. When considering your options, digital controls far surpass the performance of analog control, and will often end up being both simpler to design and even less expensive than 0-10V.

Digital controls deliver consistency by ensuring that each fixture has the same color temperature Other benefits include a reduction in the risk of installation issues while improving reliability; precise control of color temperature; and scalability for basic tunable-white or full color-gamut control. Let's walk through these benefits in more detail.

When light levels are just being adjusted up and down, it doesn't necessarily matter if the 0-10V control signal isn't precisely matched across fixtures. Particularly at high end, humans are not terribly sensitive to relative differences in light intensity. However, when control of intensity and color temperature is combined, precision is essential. Humans are more sensitive to changes in color than they are to changes in intensity. The typical margin-of-error in a 0-10V system will cause fixtures on the same control to be a different color. So the consistency delivered by a precise tunable system eliminates this issue.

Even though 0-10V is the most common control type, it's a rare project that comes to fruition without at least one wiring issue. Now, add a second set of control wires for each fixture, and the opportunity for error goes up exponentially. These errors may not always be detected by a basic function check. If the intensity and color temperature controls are crossed, a casual function check can easily miss this behavior, and the result is often a costly callback to the electrician. In addition to simpler and more robust wiring, digital controls are also immune to noise - even if your control wires are near an electrically noisy area, you will not see undesired behavior in the lighting. This has always been a benefit of digital control, but it's even more important with tunable white due to the increased sensitivity to differences in color.

The ability to set a precise and consistent color temperature at the fixture with digital controls is a huge win compared to analog control. It's important to consider, however, that when it comes to precise color temperature throughout the space, even digital controls alone may not be sufficient. For comprehensive control of color in the space, the ambient lighting from the windows must be accounted for. Combining digital color temperature control with a precision shading system enables even the most particular occupants to create the environment they need.

Finally, using a digital protocol provides the ability to deliver multiple dimensions of flexibility - in other words, digital control enables a range of solutions from simple, two-color fixtures to high-performance, precision solutions with four or more colors employed to create the desired atmosphere. Such performance with 0-10V controls requires an additional control wire for each dimension of flexibility, which is not at all practical.

As the lighting design community continues to more effectively leverage the power of tunable lighting, lighting designers, architects, and engineers will demand simple, reliable solutions that scale with their needs. Digital controls are the only way to guarantee desired results. The more we learn about how lighting affects the performance of both buildings and the people in them, the more diligent attention needs to be paid to the control systems we select for each project.

CRAIG CASEY is senior building science engineer at Lutron Electronics Co. Inc. (lutron.com).