Christmas lights

Christmas lights (also sometimes called fairy lights or twinkle lights) are strands of electric lights used to decorate homes and Christmas trees during the holiday season. Christmas lights come in a dazzling array of configurations and colors.

Contents

1 History 2 Types 3 Choice, safety 4 External Links

History

The the first known electrically-illuminated Christmas tree was the creation of Edward H. Johnson, and associate of inventor Thomas Edison. While he was vice president of the Edison Electric Light Company, a predecessor of today's Con Edison electric utility, he had Christmas tree light bulbs especially made for him. He proudly displayed his Christmas tree, which was hand-wired with 80 red, white and blue electric incandescent light bulbs the size of walnuts, on December 22, 1882 at his home on Fifth Avenue in New York. The story was published by a Detroitnewspaper reporter, and Johnson became the Father of Electric Christmas Tree Lights.

From that point on, electrically illuminated Christmas trees, indoors and outdoors, grew with mounting enthusiasm in the United States and elsewhere. In 1895, U.S. President Grover Cleveland proudly sponsored the first electrically lit Christmas tree in the White House. It was a huge specimen, featuring more than a hundred multicolored lights. The first commercially produced Christmas tree lamps were manufactured in strings of nine sockets by the Edison General Electric Co. of Harrison, New Jersey. and advertised in the Dec 1901 issue of the Ladies' Home Journal. Each socket took a miniature two-candlepower carbon-filament lamp.

Types

In modern times, Christmas lighting devices can be based on different technologies. Common technologies are incandescent light bulbs and now LEDs. Lightbulbs or LEDs are usually connected in series to be powered from mains without a transformer (LED-based strings, of course, have a current-limiting resistor). Neon lamp based strings have lamps connected in parallel, each with its own current-limiting resistor. All battery-powered lights are wired in parallel.

Other setups include lightbulb or LED-based strings with a line isolation step down transformer with bulbs or LEDs connected in parallel (LEDs have current limiting resistors). These sets are much safer, but there is a voltage drop at the end of the string (less noticeable with LED than incandescent). There is also the "wall wart" transformer which may be difficult to plug in certain places.

There are even Christmas light sets that use fiber optic. They are usually incorporated into an artificial Christmas tree. They have light bulbs or LEDs in the tree base and many fiber optic wires going to the leaves of the tree. These devices always have line isolation step-down transformer, because they have only one or two bulbs or LEDs.

Christmas lights can be animated. This is done by using special flasher or "interrupter bulbs" or electronically. An electronic Christmas light controller usually has a diode bridge followed by a resistor-based voltage divider, a filter capacitor and a fixed-program microcontroller. The animation modes are changed by pressing a button. The microcontroller has three or four outputs which are connected to transistors or thyristors. They control interleaved strings: commonly red, green, blue and yellow, or other combinations such as red, green and white.

Fiber-optic Christmas trees can also be animated electronically, but more often this is done by means of a rotating color filter disc.

Choice, safety

In the past, Christmas light sets used line-voltage (120 or 240 volts depending on what country) lightbulbs, similar to those used in refrigerators, connected in parallel. These sets were very power hungry and are used less widely nowadays. Even before that, Christmas trees were illuminated by candles. This is still done rarely, but is not recommended, because it is very dangerous!

One should always unplug a Christmas light set that has no transformer before repairing it. Remember that the electronic controller in such sets is also not line isolated! Animated Christmas light sets, including fiber optic ones should never be watched by persons having photosensitive epilepsy.

External Links

• National Electrical Contractors Association A Few Facts About The Origin Of Electric Christmas Lights (http://www.necanet.org/whats_new/report.cfm?ID=2668)
• Bill Nelson's Antique Christmas Lights site (http://www.oldchristmaslights.com/)