Engineering topics

Leon, Felipe A.

Publications and source records attributed to Leon, Felipe A..

4 records

DOE OSTI2022

Flicker: A review of temporal light modulation stimulus, responses, and measures

Flicker has been an important lighting system consideration for over a century. More precise terms are temporal light modulation (TLM) as the stimulus, and responses to TLM as the unwanted visual, cognitive, or physiological consequences. As lighting technology evolved, different forms of TLM emerged, and so did responses to them. Today, some LED systems – encompassing the LED, driver, and control – can result in TLM causing severe unwanted effects, while other LED systems produce no unwanted effects at all. LED systems can deliver a much wider range of luminous waveforms than conventional lighting systems, some exhibiting very high modulation depths. More than any light source before, they can elicit perceptions of the phantom array. Direct flicker effects at modulation frequencies less than about 80 Hz and the stroboscopic effect at frequencies greater than 80 Hz are fairly well understood, but the phantom array effect needs more exploration and characterisation. This review focuses on the technology and research history that led to current metrics for quantifying TLM and human responses to TLM. Notably, visually impaired individuals may exhibit alterations in their response to TLM, but such a discussion is beyond the intent of this review. Thus, the focus is on individuals with normal visual function.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2019

Internet of Things (IoT) Products and Applications: Lighting - Manufacturer and End-User Perspectives

It is forecast that the Internet of Things (IoT) market will experience significant growth in the coming years, with many expecting compound annual growth rates generally in the mid-20% (Forbes 2017). For lighting manufacturers, this is a tremendous opportunity to revolutionize their products to address the dwindling sales of lamps, once a major revenue stream, and bring new capabilities and services to their customers through luminaires and other lighting system components. For end-users, lighting products of the future may do more than simply provide light, with a cadre of connected sensors and controls that may help them do everything from exploring energy saving opportunities in other building systems to data-mining occupancy data to optimize use of space or increase sales. The focus of this study is to evaluate where the lighting market is today with respect to integrating IoT into its product offerings and end-user experiences with IoT, and in particular with IoT incorporated into lighting systems. The benefits, in terms of energy savings, of encouraging the adoption of connected lighting systems beyond the current solid state lighting (SSL) path to more aggressive DOE SSL Program Goals can result in an additional 33-percent of the LED energy savings, or 1.4 Quads, in 2035 (Navigant 2016).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2019

Fighting Flicker

Thanks in part to the rapid emergence of LED lighting, the phenomenon of flicker has been getting increased attention. All conventional light sources modulate luminous flux and intensity to some degree, usually as a consequence of drawing power from AC mains sources. But whereas conventional light sources have somewhat delayed responses to changes in electrical current – which serves to “cushion” them to some degree against flickering – the LED and its driver respond instantly to such changes, which can result in stark fluctuations in light output. And while these fluctuations may not be noticeable to everyone, they can still result in health and task performance problems. Understanding and countering flicker is essential to the success of high-efficiency lighting technology. That’s why the U.S. Department of Energy (DOE) Solid-State Lighting Program conducts flicker research and is supporting a number of industry committees (CIE 1-83: Visual Aspects of Time-Modulated Lighting Systems; CIE 2-89: Measurement of Temporal Light Modulation of Light Sources and Lighting Systems; and the IES Testing Procedures Committee) that are developing flicker standards for measurement, acceptability, and metrics. A wide variety of technical resources on flicker can be found at https://www.energy.gov/eere/ssl/flicker.

lighting, flicker, flicker meters, Flicker metrics↗

DOE OSTI2018

Characterizing Photometric Flicker. Handheld Meters

Temporal light modulation (TLM) is the variation of light output as a function of time and its presence can have adverse effects on health and visual performance (e.g., increased occurrence of migraines, reduced visual-task performance). TLM has been the subject of recent articles primarily associated with flicker in LED lighting. Lighting system characteristics that can affect flicker vary by technology; examples include filament thickness for incandescent sources, phosphor persistence for fluorescent and coated metal halide sources, and circuit designs for electronically ballasted or driven sources. The characterization of flicker, especially in the field, is important to ensure adequate living and working conditions. Today, various types of flicker meters are available, including high-speed and precise benchtop models for laboratory environments and portable handheld meters that can range from simple smartphone applications in an existing smart device to scientific grade meters that have capabilities beyond flicker measurements. In this report, the performance of various handheld meters capable of measuring flicker in the field is compared to a reference benchtop meter chosen based on its performance in the initial round of meter comparisons performed by Pacific Northwest National Laboratory.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗