TORRANCE, CA — July 26, 2002 — In St. Clair, Michigan the heavens appear big, bright and bold, and nowhere more so than at Bob Manning's home. At dusk the driveway
seemingly transforms into a planetarium with glowing stars, planets and moons
levitating above the background of concrete. In addition to being a passionate
astronomer, Manning is a commercial concrete contractor who wanted to differentiate
the driveway of his own home from the mundane cement slabs that he has poured
countless times. To accomplish his goal, Manning integrated into the concrete
substrate decorative lighting in the forms of celestial objects. "My aim was to
have the stars, moons and planets glow at night without overwhelming the surroundings,"
he explains. The challenge was finding the right light source. LEDs (light emitting
diodes) proved to be the ideal solution due to their resistance to environmental
stresses, low power requirements and long operating lives.
In recent years LEDs (Light Emitting Diode) have emerged from the confines
of electronic devices to become mainstream lighting tools for architects, automotive
designers and industrial lighting professionals alike. LED lamps come in a variety
of colors, sizes and standard electrical bases ranging from 3mm "grain-of-wheat"
sub-midget flange to 25mm Edison-screw based. Colors available are white, blue,
green, red, orange and yellow. LEDs are solid-state devices composed of diode
chips made from semiconductor materials that are encased in solid epoxy lenses.
Solid-state design makes LEDs impervious to electrical and mechanical shock,
vibration, frequent switching and environmental extremes. LEDs generate light
at a specific wavelength (nanometer) when current is applied. The wavelength
produced can be in either visible (400 - 700 nanometers) or infrared (830 -
940 nanometers) depending upon the semiconductor compounds used. LEDs are environmentally
friendly because they use 80% to 90% less operating power than standard incandescent
bulbs, reducing the pollution associated with generating electricity. With an
average life span of 100,000-plus hours (11 years), LEDs operate reliably year
after year. That's more than 10-20 times longer than incandescent bulbs!
Longevity of the lamps was of paramount importance to Manning because once
the concrete hardened relamping the light fixtures would be impossible. Manning
immediately eliminated incandescent lamps as a solution because, while the up-front
costs were minimal, incandescents would require periodic replacing due to their
high incidence of failure. Next, Manning considered using fiber optic lighting.
With a remote centralized light source from which light is piped down long acrylic
strands to multiple objects, fiber optic lighting made relamping a non-issue.
However, running fiber optic cables to each embedded object would cost in the
neighborhood of $6000, which was just about equal to the amount Manning budgeted
for the entire job. Utilizing the Internet, Manning set about researching other
lighting alternatives and soon discovered LEDs.
Manning found all the information he needed at the website of LEDtronics, a
premier LED lamp manufacturer located in Torrance, California. LEDtronics manufactures
thousands of different LED products ranging from discrete surface mount indicators
to direct incandescent replacement LED lamps. The LEDtronics website - www.ledtronics.com
- offers comprehensive information on LED technologies, products and applications.
The site includes tools for cross-referencing incandescent lamps to their LED
equivalents, and for calculating the power savings accrued by replacing incandescents
with LEDs. LEDtronics provides specifications online of all their LED products.
"That's what is great about the LEDtronics website, I was able to look
at the specs before I placed the order. I saved a few bucks and a lot of time
by ordering the right stuff from the start," says Manning.
He liked what he read: Lamps that provide years of reliable performance. With
an average operating life of 11 years (100,000-hours), LEDs fulfilled Manning's
need for a durable lighting solution. Since LEDs are solid-state lights with
no filaments or glass tubes to break they could withstand the vibrations from
motor vehicles in the driveway, the temperature changes of Michigan's seasons,
and the frequent switching of everyday use. Manning calculated that if the LEDs
burned for eight hours per night they would last for the life span of the average
concrete driveway - 30-plus years! What further convinced Manning that LEDs
were the best solution for his application were the sustained color fidelity
and energy efficiency that LEDs provide. While incandescent bulbs can waste
90 percent and more of the energy they received in the generation of heat and
in light blocked by lenses or filters, LEDs deliver 100 percent of their energy
as light.
Manning purchased 32 Snap-in ½-inch Top Hat Panel Mount LEDs. (LEDtronics
part numbers PF50CW1K white and PF50CB1K blue, sixteen of each color) The LED
lamps feature one LED chip, six-inch wire leads and clear lenses. They are rated
for incoming voltages of 12/14Volts DC. Built-in current-limited resistors eliminate
the need for any circuit modifications. Blue LED lamps emit light at 470 nanometers,
produce 3000 millicandela at 20mA and have a 15-degree viewing angle. White
lamps produce an 8000K cool-white light, 6000 millicandela at 20mA and have
a 20-degree viewing angle. The diode chips are composed of Silicon Carbide on
a Gallium Nitride substrate.
Constructing the luminaries involved some handiwork on Manning's part. First,
he had a local plastics company mill the stars, moons and planets from a clear
acrylic polymer. The finished forms measured five inches in diameter by one
and one half-inches thick. Manning drilled a 9/16-inch hole in each form, inserted
one LED lamp, and applied silicon to waterproof each connection. The assemblies
were then connected to four-inch wire chairs that had been positioned in the
underpinning for the concrete bed. Since LEDs are voltage-sensitive, Manning
hooked up the electrical circuit to a power supply calibrated to output precisely
13 volts. After testing the LEDs, the concrete was poured and allowed to cure.
A few days later, Bob turned on the luminaries. "The end result produced the
WOW effect I was hoping for," says Manning, pleased with the outcome.
Successfully fulfilling Manning's vision of a driveway that reflects his interests
and transcends the typical cement slab relied on the strengths of LED lighting:
100,000-hour operating life, energy efficiency and solid-state design. As Bob
Manning's application demonstrates, that the sky's the limit for LED technology!
