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, mostly in the West. Christmas lights come in a dazzling array of configurations and colors.

History

The first known electrically-illuminated Christmas tree was the creation of Edward H. Johnson, an 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 City. Local newspapers ignored the story, seeing it as a publicity stunt. However, it was published by a Detroit newspaper 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 multiples of eight sockets by the General Electric Co. of Harrison, New Jersey. Each socket took a miniature two-candlepower carbon-filament lamp.

Over a period of time, strings of

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 technology. 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

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

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.

The number of strands of continuous light sets that may be safely conjoined varies based on whether the lights are LEDs, ordinary miniature light bulbs, or the larger C7/C9 type light bulbs. Other factors include the voltage of the set and the size of the wiring in the set. If you have questions, consult the manufacturer's instructions or an electrician.

Most light sets come with built in fuses to help protect against overheating and to prevent your house's fuses or circuit breakers from being tripped. If you blow a fuse, unplug the strand from the power source and reduce the number of lights immediately. If the strand has nothing attached, or has blown repeatedly, the strand may contain a short and should be discarded.

It should also be noted that many light sets may contain traces of lead, and consumers should wash hands thoroughly after handling these products, especially before eating. Proposition 65 of California requires that if products contain lead or traces of lead then a warning must be printed on packing of products. Be sure to check the label for this and any additional warnings.

House lights

In the U.S. from the 1960s, beginning in tract housing, it became increasingly the custom to completely outline the house (but particularly the eaves) with weatherproof Christmas lights. The Holiday Trail of Lights is a joint effort by cities in east Texas and northwest Louisiana that had its origins in the Festival of Lights and Christmas Festival in Natchitoches, started in 1927, making it one of the oldest light festivals in the United States.

The rule of thumb for fairy lights when decorating trees is to use between 150 and 300 lights per foot of tree heights.

Trivia

• Christmas light strings wired in series were often of the type where if one bulb burned out or was loose, an entire string would not illuminate. Development of wiring in parallel and shunts in individual bulb bases were technological (and practical) improvements welcomed by many users.

• In the 1989 film National Lampoon's Christmas Vacation, actor Chevy Chase attempts to follow American family Christmas traditions with elaborate Christmas lights and decorations on the exterior of the family home. His attempt at a "Grand Illumination" for a family reunion is one of the high points of the story. The film has become an annual holiday favorite in many families.

• The Oklahoma alternative rock band Flaming Lips becamse known in their early days for covering their instruments in christmas lights.

External links