Fighting Flicker - Energy Focus

Fighting Flicker The Causes and Effects of Flicker in Lighting

A Roundtable Discussion About Light, Health and the LED Revolution July 17, 2018

© 2017 Energy Focus, Inc.

Speakers

John Davenport Chief Scientist Energy Focus Inc.

Laszlo Takacs Chief Technology Officer Energy Focus Inc.

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Speakers

Naomi J. Miller (FIES, FIALD, LC) Senior Scientist Pacific Northwest National Laboratory

Yumi Alanoly Product Marketing Manager Energy Focus Inc.

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Agenda 1.  What is Flicker in Lighting? 2.  Why Should I Care About Flicker? 3.  How to Verify Flicker 4.  What Can I Do About Flicker? 5.  Questions and Answers

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© 2017 Energy Focus, Inc. 5

What is Flicker? Temporal light artifact (TLA)*: an undesired change in visual perception induced by a light stimulus (Temporal Light Modulation, TLM) whose luminance or spectral distribution fluctuates with time

•  Visible Flicker: Perception of visual unsteadiness… for a static observer in a static environment. Up to 3 - ~80 Hz

•  Stroboscopic effect: change of motion perception… for a static observer in a non-static environment ~80 Hz - ~2000 Hz

•  Phantom Array effect (ghost effect): change in perceived shape or spatial layout of objects… for a non-static observer in an otherwise static environment (e.g. saccade, normal head movement, or while driving) ~80 Hz – ~2500 Hz

* CIE 17.443 e-ILV definitions http://www.lrc.rpi.edu/programs/solidstate/assist/flicker.asp https://www.led-professional.com/resources-1/articles/lighting-with-leds-2013-more-than-just-illuminating-objects



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How Flicker Effects Your Health

If a light source is flickering faster than 50-90 cycles per second, this imperceptible flicker is still detected by our nervous system as modulation in light. Visual and imperceptible flicker can have a negative impact on the physiology of our brain and cognition.

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How Flicker Effects Your Health

According to to IEEE (Institute of Electrical and Electronics Engineers), potential flicker-induced Impairments include*: •  Neurological problems, including epileptic seizure •  Headaches, fatigue, blurred vision, eyestrain •  Migraines •  Reduced visual task performance •  Increased autistic behaviors, especially in children •  Distraction

“Flicker—Understanding the New IEEE Recommended Practices” (http://energy.gov/sites/prod/files/2015/05/f22/miller%2Blehman_flicker_lightfair2015.pdf), DOE & Pacific Northwest National Laboratory


How Flicker Effects Your Safety

Flicker may affect safety: •  In an industrial setting, possible hazard from

stroboscopic effect: rotating or translating machinery may look like it’s moving at a different rate

•  In nighttime driving, the phantom array effect can distract a driver from seeing important details on or near the roadway

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How Flicker Effects Your Electronics

•  Flicker may interfere with barcode scanners and video/photography equipment

•  FCC & CISPR guidelines for low EMI & RFI could cause disruption to electronic devices and wireless communication (including medical equipment)

•  Flicker may produce distortion and electronic pollution that could interfere with medical equipment

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Especially Important to Discuss for LEDs

•  Incandescent lamps typically fairly low < 10% flicker •  Fluorescent

•  Magnetically ballasted <40% •  Electronically ballasted <20%

•  LEDs – anything between 0 and 100%

Because LEDs reacts quickly light flicker is entirely dependent on how well the circuit driving the LEDs holds the LED current constant even as the power line current goes to zero 120 (or 100) times per second



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Measuring Flicker, older metrics •  Percent flicker

•  0-100% scale. Older metric, but more well-known and more commonly used

•  Accounts for average, peak-to-peak amplitude •  Does not account for shape, duty cycle, frequency

•  Flicker index •  0-1.0 scale. Newer, but less well-known and rarely

used •  Accounts for average, peak-to-peak amplitude, shape,

duty cycle •  Does not account for frequency

•  IEC Pst – “Flickermeter” (LRC Assist Mp metric similar) •  “Limitation of voltage changes, voltage fluctuations and

flicker” in public electric supply systems, up to 80 Hz

https://www1.eere.energy.gov/buildings/publications/pdfs/ssl/flicker_fact-sheet.pdf

Source: IES Lighting Handbook, 10th Edition •  Percent Flicker = •  Flicker Index =

BABAx

+

−%100

Area1Area1+ Area 2


Measuring Flicker, Other metrics


•  IEEE Standard P1789-2015 •  Focused on health risks from flicker, so it’s more conservative than

for visibility alone •  Plotted % Flicker (modulation) and frequency for no effect level and

low risk level. Simple metric. •  Hard to evaluate complex waveforms, doesn’t account for wave

shape, doesn’t account for low duty cycle (e.g., dimming). •  Stroboscopic effect Visibility Measure (SVM)

•  Predicts visibility of strobe effect based on wave shape and duty cycles, above 80 Hz.

•  Uses Fast Fourier Transform (FFT) analysis •  Not complete. Fixed gaze only. No account for sensitive individuals

or phantom array effect. Assumes flicker visibility = neurological effect.

NEMA-77-2017 is a combo of Pst and SVM. A group of manufacturers has signed on to this standard as a first step.


Measuring Flicker

Edison Tech Center. “The Fluorescent Lamp” http://www.edisontechcenter.org/Fluorescent.html. Temple Grandin (1995)

•  Older magnetically-ballasted fluorescent lighting can produce 120 Hz flicker with up to 40% modulation. Many people despised fluorescent lighting because of older flickering systems.

•  Newer electronically-ballasted fluorescent lighting operates at 40 kHz or more, but may have a 120 Hz component that exhibits 10% flicker.

•  Lighting system flicker can be measured with an inexpensive oscilloscope and photocell.

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Two easy tests: #1 Slow Motion Video

Slow Motion Smartphone Video •  Simple – just point, shoot and playback •  Works well for 120 Hz or 100 Hz flicker •  Reduces the light variation rate enough so that we become consciously

aware of the light pulsing •  The brighter the pulsing, the more significant the effect •  Sensitive from about 10% to 100% flicker


What Does Flicker Look Like? Flicker is described as variations in luminance over time (IEEE 1789-2015). Flicker in LED lighting occurs as a result of the LED driver converting AC power to DC power. Modulating the current to produce lower flicker is the challenge that all lighting solutions are faced with.

<1% Flicker ~60 % Flicker ~50% Flicker

Flicker at 120 Hz slowed to ~ 2.5 Hz

© 2017 Energy Focus, Inc. 18 7/18/18

Slow Motion Video

Why Slow Motion Smartphone Video is Valuable

•  The light variation the video reveals is the light variation your eyes and brain are actually being subjected to.

•  Light modulation particularly impacts people doing tasks which involve rapid eye movement – e.g. reading (Wilkins).

•  If you see pulsing, the flicker level is probably too high – at least for a significant subset of the population (IEEE 1789).

Limitations – Frequencies below about 200 Hz; not quantitative

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Two easy tests: #2 “DIY” Portable Flicker Meter Example

Portable Flicker Meter

•  Low cost compared to laboratory “waveform” based meters •  Portable / useful for evaluating lamps •  Works well for all types of flicker •  Displays the light level through the entire flicker period •  Quantitative – e.g. percent flicker 1-100

This “DIY” Meter Uses: o  DSO Nano Oscilloscope v3 o  Solar cell (from a LED Solar Powered Landscape Light) o  Custom programming to calculate % flicker


What Does A Flicker Measurement Look Like?

https://www.energy.gov/sites/prod/files/2018/05/f51/lfi2018_miller_0.pdf

Legacy

LED

%F = 6.6% FI = 0.02

%F = 37% FI = 0.11

%F = 1.8% FI = 0.00

%F = 97.2% FI = 0.39

%F = 1.7% FI = 0.00

%F = 22% FI = 0.057


What Does A Flicker Measurement Look Like

https://www.energy.gov/sites/prod/files/2018/05/f51/lfi2018_miller_0.pdf

Using the Portable Flicker Meter

%F = 10%

Electronically ballasted CFL


How Much Flicker Is Okay? •  IES and CIE are developing application standards •  IEEE group published their P1789 recommended practice for evaluating

flicker in 2015, but it does not differentiate flicker thresholds based on application

•  The EPA, ENERGY STAR® and California Title 20 programs are considering the adoption of flicker criteria, require reporting of flicker metrics, or have already adopted metrics and thresholds.


The lower the % flicker value, the better. The lower the flicker index value, the better.

The higher the frequency the better for health and wellness.



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Achieving Flicker-Free LED Technology

Older Tech New Technology TLEDs

Vs


Investment to Remove Flicker

Removing the output ripple from a driver is not automatic. Additional circuitry must be introduced to regulate this into a stable, direct current.


What You Can Do Now

•  Evaluate products in person and learn to test for flicker

•  Follow recommended flicker guidelines, such as IEEE P1789-2015 or NEMA 77-2017, or both

•  Ask manufacturers to:

•  Provide flicker measurements (over the full dimming range)

•  Present tests that demonstrate driver performance

•  Third Party Verification


Third Party Flicker Verification is Important

We rely on 3rd parties for electrical safety.

Why not use 3rd parties to assure safe flicker levels ?



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Questions and Answers

Join the LED “Flicker-Free” Revolution!


Contact Us https://www.energyfocus.com/contact-us/

Phone Number: 800-327-7877

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Thank You!

Flicker - What You Can’t See CAN Hurt You

© 2017 Energy Focus, Inc. 33 7/18/18

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www.bauarchitecture.com/research.daylightleds.shtml 6.  Irlen Institute. “What is Irlen Syndrome?” http://irlen.com/what-is-irlen-syndrome/. 7.  Graph 1: Popular Mechanics: The Ultimate Light Bulb Test http://www.popularmechanics.com/technology/gadgets/reviews/g164/incandescent-vs-compact-fluorescent-

vs-led-ultimate-light-bulb-test/. 8.  US Department of Energy “Solid-State R&D Plan” May 2015. 9.  Lucas, Robert J et al. “Measuring and using light in the melanopsin age” Trends in Neurosciences Vol 37 No 1. 2014. 10.  Holzman, David C. “What’s in a Color? The Unique Human Health Effects of Blue Light” Environmental Health Perspectives Vol 118 No 1. 2010. 11.  Hawes, Breanne K., et al. “Effects of four workplace lighting technologies on perception, cognition, and affective state” International Journal of Industrial Ergonomics

Vol 42. 2012. 12.  Meesters, Ybe et al. “Low-intensity blue-enriched white light (750 lux) and standard bright light (10000 lux) are equally effective in treating SAD. A randomized

controlled study” BMC Psychiatry. 2011. 13.  US Department of Energy. “Flicker” Building Technologies Office Solid-State Lighting Technology Fact Sheet. 14.  Loew et al. “Symptoms of Meares-Irlen/Visual Stress Syndrome in subjects diagnosed with Chronic Fatigue Syndrome” International Journal of Clinical and Health

Psychology Vol 14 ppp87-92. 2014. 15.  Ameritech Energy. “Flicker Free – Important Design & Buyer Information” Solid-State Lighting Technology Fact Sheet. http://www.energyfocusinc.com/lighting-and-

your-health/ 2014. 16.  Roberts, Joan E. “Light and Immunomodulation” Annals New York Academy of Sciences. 2000. 17.  Rensselaer Polytechnic Institute. “Chapter 16: Human eye sensitivity and photometric quantities”

http://www.ecse.rpi.edu/~schubert/Light-Emitting-Diodes-dot-org/Sample-Chapter.pdf 18.  Salva et al. “Circadian rhythms, melatonin and depression” Cur Pharm Des vol. 17 no. 15. 2011. 19.  Mohammadizadeh et al. “Is the light-emitting diode a better light source than fluorescent tube for phototherapy of neonatal jaundice in preterm infants?” Adv Biomed

Res vol. 1 no. 51. 2012. 20.  World Health Organization. “LED phototherapy for neonatal jaundice” Compendium of innovative health technologies for low-resource settings 2013. 21.  Sawyer. “Phototherapy for Jaundice” Medscape http://emedicine.medscape.com/article/1894477-overview 2013. 22.  Smil, V. 2014. The long slow rise of solar and wind. ,Scientific American 282 (1):52-57; EIA 2013 Energy Book; “Lighting The Way 2013”, McKinsey Inc.

Fighting Flicker - Energy Focus

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