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Publication Title | LED Lighting Shootout

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Here is a lighting test—which lighting technology can produce the most light for the least power?

The hands down winner is the light emitting diode (LED) which makes three times more light per watt than a compact fluorescent and 30 times more than a standard incandescent.

What is an LED?

Just as its name, light emitting diode, implies, the LED is an electronic diode not much different from any other semiconductor diode. What makes an LED special is that its semiconductor junction is designed to convert current flow into visible light. LEDs have been around as discrete colored lights for quite awhile. Just about everyone is familiar with the LED as indicators on electronics. They came in various colors such as red, green, and yellow. Recent advances have made blue and now, finally, white light available from LEDs. The intensity of the LEDs light output is also increasing rapidly. Modern LEDs can have over a hundred times more light output than those available ten years ago. It is now possible to assemble lighting from a collection of LEDs.

The LED is inherently a low voltage DC device. LED junctions operate at between 1.8 VDC to just over 3.1 VDC. This junction voltage drop is built into the physics

of the diode. While different colored LEDs have different junction voltage drops, they all fall into the 1.8 to 3.1 VDC range. When it comes to using LEDs efficiently, the data here shows that they are best employed using low voltage DC as a power source.

The LED has several advantages in addition to high efficiency electricity to light conversion. The LED is the longest lived light making device ever invented. LEDs now commonly last 500,000 hours before failure. With use every night, all night, this means that an LED will last for over 100 years! Physically the LED is very rugged and can withstand moisture, vibration, and shocks which would easily destroy a compact fluorescent or incandescent lamp. The LED lamps also produce no radio frequency interference (RFI), while the same cannot be said for many compact fluorescents.

I’ve been using LED lights around our home for several years and decided it was time measure their performance against other efficient lighting technologies.

The Test Jig

I set up the simple light testing jig shown in the illustration here. I designed this particular test jig to simulate a desk lighting situation or reading in a chair situation. I used a Greenlee Textron model 93-1065F Digital Illuminometer to measure the light output of the various lamps tested. This light meter is designed to measure light levels from lighting fixtures for the purpose of verifying that lighting specifications or

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Richard Perez ©1997 Richard Perez

Home Power #60 • August / September 1997 33

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