NICOR White Paper
Flicker: Common Causes and How to Avoid It
NICOR®, Inc.
2200 Midtown Place NE
Albuquerque, NM 87113
800.821.6283
www.nicorlighting.com
By Mike Garcia
11/05/2014
Figure 1: Demonstrating Stroboscopic Effect by rapidly moving an object under two
light sources with different % Flicker. The light source on the left is the Nicor DLR56
with a %Flicker of 18.9% and the light source on the right is an AC driven LED circuit
with a %Flicker of 99%.
INTRODUCTION
Lighting is an important part of our
lives. For billions of years the sun has
provided a constant light source that life
on earth has adapted to, which is why it is
important to us as humans to have a light
source that does not waver in its intensity.
With each new lighting technology there
are many obstacles to overcome. Flicker
has been a long standing issue because
our power is transmitted at a frequency
of 50Hz or 60Hz depending on your
geographic location.
Since there is no industry standard
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to specify the amount of flicker that is
acceptable we will discuss a few different
metrics in order to quantify flicker; %
Flicker and Flicker Index.
we call flicker. Flicker is a variation of
light intensity over time commonly
caused by artificial light sources such as
incandescent, fluorescent, and LEDs.
In spite of the lack of flicker acceptability
standards, it is important to purchase
lights with a low % Flicker to ensure the
highest quality of light. Flicker can have
health impacts and cause certain people
to feel uneasy when subjected to it.
Stroboscopic Effect can be easily seen by
observing objects in motion under a light
source. An object in motion observed
under a light source with no flicker will
appear blurry, an object observed under
a light source with flicker will appear
multiple times as seen in Figure 1.
What is Flicker and Stroboscopic Effect:
Flicker, shimmer, and strobe are some
common terms used to refer to what
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Health Impact:
Research has shown that flicker above
100Hz can generally not be noticed, but
stroboscopic effects can be perceived
up to 500Hz. Flicker has been known
to cause symptoms such as headaches,
migraines, eye strain, distraction, and
in frequencies between 3Hz and 70Hz,
epileptic seizures.
Flicker Index: 0.04
Percent Flicker: 13.4
Figure 2: Example of how to calculate % Flicker
and Flicker Index
Figure 3: Flicker from an A19 style Incandescent
light bulb.
Quantifying Flicker:
There are several ways to mathematically
describe flicker, and although we have
a great scientific understanding of it,
Flicker Index: 0.11
Percent Flicker: 37.0
Figure 4: Flicker from a Quad Tube style
Magnetically-ballasted CFL light bulb
there is no standard set for acceptable
amounts of it due to its subjective nature.
The most popular method is defined
by the Illuminating Engineering Society
(IES) in the RP-16-10 standard, where
the percentage of flicker is calculated by
difference of maximum and minimum
amplitude divided by the sum of
maximum and minimum as seen in the
equations in Figure 2. The flicker index is
calculated by dividing the area above the
average light output by the sum of the
area above and below the average light
output. Both methods are illustrated in
Figure 2.
Flicker Index: 0.01
Percent Flicker: 5.1
Figure 5: Flicker from an A19 style Electronicallyballasted CFL light bulb
Flicker inVarious Light Sources:
Nearly every light source driven from line
voltage has some level of flicker, Figures
3 - 7 demonstrate the intensity and
frequency of various light sources and
their correlating Flicker Index and Percent
Flicker as obtained from the Department
of Energy. Figures 6 and 7 demonstrate
the differences in flicker between the same
types of bulbs manufactured by different
companies.
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Flicker Index: 0.20
Percent Flicker: 93.2
Figure 7: Flicker from a different R30 style LED light
bulb Brand B.
Flicker Index: 0.06
Percent Flicker: 22.7
Figure 6: Flicker from a R30 style LED light bulb
Brand A.
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As seen in these examples, flicker can be
over 90% and still be acceptable in the
marketplace. In certain applications, such
as outdoor lighting, a higher amount of
flicker can be acceptable. In settings such
as offices and schools, flicker is much less
acceptable because of the associated
negative side effects.
Flicker Index: .029
Percent Flicker: 10
Flicker Index: .062
Percent Flicker: 18.9
Figure 8: Flicker from Nicor DLR56
Figure 9: Flicker from Nicor DLS56
Figures 8 -10 illustrate data taken on various Nicor|LED products. When comparing
the Nicor|LED products in Figures 8-10 to the LED light sources in Figures 6 and 7 it
can clearly be seen that there is substantially less flicker. To better understand the
comparison you can refer to Figure 1, the image on the left is light from the Nicor|LED
DLR 56, the image on the right is a light source with a flicker index similar to Figure 7.
Flicker Index: .059
Percent Flicker: 19
Figure 10: Flicker from Nicor DEB 56
Dimming and Flicker:
internal circuitry and require extra wire to
be run for control. TRIAC dimmers on the
There are several methods used to dim
LED light sources, among the most popular other hand are less expensive, but need to
be matched with compatible luminaires
being TRIAC dimming, generally found in
to ensure there is minimal flicker at every
residential settings, and 0-10V dimming,
dimmed level.
generally found in commercial settings.
TRIAC dimmers are the most common type
Each type of dimmer has pros and cons
of dimmers found in residential lighting
when it comes to flicker. Dimming with
0-10V tends to have less flicker, but is more and operate by cutting the leading edge
of the line voltage as seen in Figure 12.
costly because the luminaires have extra
Figure 11: Line voltage as seen before TRIAC
dimming.
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Figure 12: Line voltage being chopped in half by
TRIAC dimmer circuit.
Flicker tends to happen at the lower end of
dimming because more of the line voltage
is cut out as seen in Figure 13. Sometimes
the abrupt leading edges from the TRIAC
dimmer cause current spikes across
the LEDs creating variations in the light
output.
Figure 13: Line voltage being chopped to a minimum by TRIAC dimmer circuit
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When a dimmer is not compatible with a luminaire you can see a slow flicker as
illustrated in Figure 14. The flicker in Figure 14 is shining approximately 60% brighter at
a frequency of approximately 1Hz. LED compatible dimmers have a knob to trim up the
low end so that the end user can eliminate flicker and set the minimum dimmable level.
Mitigation:
When using TRIAC dimmers it is extremely important that the dimmer and luminaire
are matched by the recommendation of the manufacturers. Energy Star states that each
luminaire is required to have a minimum of 3 compatible dimmers. Not following the
manufacturer’s dimmer recommendation can often cause flicker and other maladies
such as drop out and strobing. Flicker and drop out can also be minimized by wiring
several luminaires to a single TRIAC dimmer.
Flicker may remain an issue until a new technology is more widely used than TRIAC
dimmers, luminaire and dimmer manufacturers work together to help eliminate such
issues or a new technology is developed to handle the multitude of TRIAC dimmers
available on the market.
Figure 14: Flicker from a dimmed light source at a
frequency of approximately 1Hz
Summary:
Due to the adverse side effects from flicker that some people experience it is important
for the consumer to purchase LED products with minimal flicker and use dimmers from
the manufacturers recommended list. When purchasing LED products it is important to
understand that standards have not been set for the amount of acceptable flicker and
further research may need to be done by the consumer to find out how much flicker a
product has.
Nicor|LED products go through a battery of dimmer and flicker tests to ensure that they
work with the largest variety of dimmers possible. Flicker data is taken on each product
so there is no doubt the amount of flicker is acceptable by Nicor standards, providing
some of the highest quality light in the industry.
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References:
http://www.lrc.rpi.edu/programs/solidstate/
assist/pdf/AR-Flicker.pdf
http://grouper.ieee.org/groups/1789/
FlickerTR1_2_26_10.pdf
http://apps1.eere.energy.gov/buildings/
publications/pdfs/ssl/flicker_fact-sheet.pdf
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