faces of the future - Illuminating Engineering Society

LED WATCH
The Standards Wave
BY JAMES BRODRICK
Rolls On
At the movies, we get so caught
up in the on-screen action that we
seldom think about all the months of
behind-the-scenes work that made
our two hours of cinematic enjoyment
possible—much less about the
army of people who patiently and
painstakingly carried out that work.
Not just the producer, director and
screenwriter, but also those unsung
heroes—from the art director, to
the set designer to the gaffer—who
played far less glamorous roles.
So it is with a technology like solid-state
lighting (SSL). Most people
focus only on the “wow factor” of the
end product, without considering all
the little things that lie behind it. One
of the most important of those “little
things” is standards, which play a
huge role in the development of any
technology. Without standards and
test methods to consistently characterize
product performance and
assure safety, an “anything-goes”
mentality could create widespread
confusion and make things difficult
for manufacturers, consumers and
specifiers alike.
And that’s just what happened
in the early years of SSL, which
were likened more than once to the
Wild West. But recent progress in
standards development has brought
a semblance of law and order to
Dodge City, thanks to the coordinated
efforts of such organizations as
the IES, NEMA, American National
Standards Lighting Group (ANSLG),
American National Standards
Institute, National Institute of
Standards and Technology (NIST),
Underwriters Laboratories, International
Electrotechnical Commission,
International Commission on
Illumination (CIE) and Canadian
Standards Association.
These groups have helped develop
standards that have already
addressed many key aspects of
SSL—from nomenclature, to chromaticity
and performance specifications,
to power supply and safety.
Two of the most important of these
standards have come from IES: LM-79
specifies a standard test method for
measuring the photometric and electrical
properties of SSL devices in
order to compare light output and calculate
luminaire efficacy, while LM-80
lays out procedures for measuring
lumen degradation over time, a key
component of reliability and lifetime.
Both are up for their regularly scheduled
two-year reviews, with committees
already formed and well-armed
with lists of newly surfaced issues
that may need to be addressed by
updates that enable the standards
to keep pace with a rapidly evolving
technology.
TWO ON THE WAY
Two related standards from
NEMA, which have been in development,
are nearing publication. SSL-1,
“Electronic Drivers for LED Devices,
Arrays, or Systems,” is in the balloting
stage and is expected to be published
by the end of the year. A logical
sequel to LM-79, which looks at lamp
performance, SSL-1 focuses on the
driver, which many feel is the weakest
link in the SSL luminaire chain.
The idea is to create some standards
around drivers so that they live up to
the same lifetime claims as the LEDs.
What good are LEDs that last for
50,000-plus hours, if they depend on
a driver that lasts only 30,000 hours
About as good as the proverbial cow
that yields the sweetest milk in town
but has an unfortunate habit of kicking
the pail over.
SSL-6, “Solid State Lighting
for Incandescent Replacement-
Dimming,” looks at another issue
that’s been getting quite a bit of
attention lately, namely, controllability.
Many people assume that all
LEDs are easily dimmable, but in
fact that only holds true if the LED
has an electronic driver with dimming
capability and the driver is
compatible with the chosen dimming
control. SSL-6 provides interface
recommendations for dimming
control of integrated LED lamps
intended to replace general service
incandescent products. Like SSL-1,
SSL-6 is in the balloting stage and
should be published by year’s end,
after which NEMA plans to initiate
additional dimming standards. Both
standards—SSL-1 and SSL-6—have
been long-awaited and are sure to
make a big difference when they’re
published, because they’ll be filling
what amounts to a huge void.
THE QUESTION OF LIFETIME
Still another much-anticipated
solid-state lighting document, which
22 www.ies.org