Edison screw - AbsoluteAstronomy.com

The Edison screw fitting is a system of connectors used for light bulbs, developed by Thomas Edison

Thomas Edison

Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...

and licensed starting in 1909 under the Mazda

Mazda (light bulb)

Mazda was a trademarked name created by the Shelby Electric Company for incandescent light bulbs. The name was used from 1909 through 1945 in the United States by Shelby and later General Electric; Mazda brand light bulbs were made for decades after 1945 outside the USA...

trademark

Trademark

A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...

. Most have a right-hand threading, so that it goes in when turned clockwise

Clockwise

Circular motion can occur in two possible directions. A clockwise motion is one that proceeds in the same direction as a clock's hands: from the top to the right, then down and then to the left, and back to the top...

and comes out when turned counterclockwise, like a hardware

Hardware

Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....

screw

Screw

A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...

. There are rare instances where these are reversed to deter theft

Theft

In common usage, theft is the illegal taking of another person's property without that person's permission or consent. The word is also used as an informal shorthand term for some crimes against property, such as burglary, embezzlement, larceny, looting, robbery, shoplifting and fraud...

, so that they cannot be used in other light fixture

Light fixture

A light fixture, light fitting, or luminaire is an electrical device used to create artificial light and/or illumination, by use of an electric lamp...

s.

Screw bases suffer from two disadvantages. Firstly, the metal screw itself forms one of the contacts for the circuit. If the lighting system is not correctly wired, or a lamp is plugged into a non-polarized outlet, the metal screw can become energized, presenting an electric shock

Electric shock

Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....

hazard to anyone attempting to change the bulb. Secondly, if the bulb unscrews in the socket for any reason, it can lose contact with the center contact and stop working until it is screwed in tighter. This is not always a disadvantage, however: it provides a method for turning a single bulb off without using a wall or fixture switch, with appropriate precautions against the high heat of the bulb.

History

Early U.S. lamp manufacturers used different and incompatible bases. The Thomson-Houston Electric Company

Thomson-Houston Electric Company

The Thomson-Houston Electric Company was a manufacturing company which was one of the precursors of the General Electric Company.The Thomson-Houston Electric Company was formed in 1883 in the United States when a group of Lynn, Massachusetts investors led by Charles A...

used a threaded stud at the bottom of the socket, and a flat contact ring. The Sawyer-Mann or Westinghouse

Westinghouse Electric (1886)

Westinghouse Electric was an American manufacturing company. It was founded in 1886 as Westinghouse Electric Company and later renamed Westinghouse Electric Corporation by George Westinghouse. The company purchased CBS in 1995 and became CBS Corporation in 1997...

base used a spring clip acting on grooves in the bulb base, and a contact stud at the bottom of the lamp. By about 1908 the Edison base was most common, with the others falling out of use.

In response to Edison's patent

Patent

A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

, Reginald Fessenden

Reginald Fessenden

Reginald Aubrey Fessenden , a naturalized American citizen born in Canada, was an inventor who performed pioneering experiments in radio, including early—and possibly the first—radio transmissions of voice and music...

invented the bi-pin connector for the 1893 World's Fair. Other lamp bases include the bayonet mount

Bayonet mount

A bayonet mount or bayonet connector is a fastening mechanism consisting of a male side with one or more pins, and a female receptor with matching L slots and spring to keep the two parts locked together....

and wedge base

Wedge base

A wedge base is a type of electrical connector used as a fitting for small light bulbs. It is similar to the bi-pin connector, except that the two "pins" are the same wires that extend into the bulb , and the wires are bent up onto the sides of the base, where they make contact with the socket...

Sizes and applications

Dimensions and tolerances for screw bases are standardized in ANSI

Ansi

Ansi is a village in Kaarma Parish, Saare County, on the island of Saaremaa, Estonia....

standard C81.67 and IEC

IEC

-Organisations:* Independent Electoral Commission * Independent Electrical Contractors, a U.S. national trade association.* Institut d'Estudis Catalans , a Catalan academic institution....

standard 60061-1. The two standards have mostly been harmonized, although several types exist in only one of the two standards with no equivalent in the other.

The designation Exx refers to the diameter

Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...

in millimeters, even in the U.S., where the bulb glass

Glass

Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

is listed in eighths of an inch. (For example, E12 has a diameter of 12 mm.) There are four common sizes of screw-in sockets used for line-voltage lamps:

candelabra
Candelabra
"Candelabra" is the traditional term for a set of multiple decorative candlesticks, each of which often holds a candle on each of multiple arms or branches connected to a column or pedestal...

: E12 North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, E11 in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
intermediate: E17 North America, E14 (SmallES) in Europe
medium or standard: E26 (MES) in North America, E27 (ES) in Europe
mogul: E39 North America, E40 (GoliathES) in Europe.

Other screw thread sizes exist for other uses.

The large E39 is used on street light

Street light

A street light, lamppost, street lamp, light standard, or lamp standard is a raised source of light on the edge of a road or walkway, which is turned on or lit at a certain time every night. Modern lamps may also have light-sensitive photocells to turn them on at dusk, off at dawn, or activate...

s, and high-wattage lamps (such as a 100/200/300- watt three-way) and many non-incandescent high-intensity discharge bulbs. In areas following the National Electrical Code general-use lamps over 300W cannot use an E26 base and instead use the E39 base, 300W lamps may use either base. Medium Edison screw (MES) bulbs for 12 V are also produced for recreational vehicle

Recreational vehicle

Recreational vehicle or RV is, in North America, the usual term for a Motor vehicle or trailer equipped with living space and amenities found in a home.-Features:...

s. Large outdoor Christmas lights use an intermediate base, as do some desk lamps and many microwave oven

Microwave oven

A microwave oven is a kitchen appliance that heats food by dielectric heating, using microwave radiation to heat polarized molecules within the food...

s. Previously, emergency exit

Emergency exit

An emergency exit in a structure is a special exit for emergencies such as a fire: the combined use of regular and special exits allows for faster evacuation, while it also provides an alternative if the route to the regular exit is blocked by fire, etc....

signs also tended to use the intermediate base, but U.S. and Canadian rules now require long-life and energy-efficient LED

Light-emitting diode

A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...

lamps, which can be purchased inside a bulb as a retrofit

Retrofit

Retrofitting refers to the addition of new technology or features to older systems.* power plant retrofit, improving power plant efficiency / increasing output / reducing emissions...

. A medium screw base should not carry more than 25 ampere

Ampere

The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...

s current; this may limit the practical rating of low voltage

Low voltage

Low voltage when used as an electrical engineering term concerning an electricity supply grid or industrial use, broadly identifies safety considerations of the system based on the voltage used. The meaning of the term "low voltage" is somewhat different when used with regard to a more typical end...

lamps.

In countries which use 220–240 volts AC

Alternating current

In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

domestic power, E27 and E14 are the most common sizes, although the bayonet mount

Bayonet mount

is also used. In 120-volt North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

and 100-volt Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, the standard size for general-purpose lamps is E26. E12 is typically used for candelabra fixtures. E17 is also sometimes used, especially in small table lamps and novelty lighting, and occasionally the lights on newer ceiling fan

Ceiling fan

A ceiling fan is a fan, usually electrically powered, suspended from the ceiling of a room, that uses hub-mounted rotating paddles to circulate air....

s. Christmas lights

Christmas lights

Christmas lights are lights used for decoration around Christmas. The use of decorative, festive lighting during the Christmas holiday season is a long standing tradition in many Christian cultures, and has been adopted as a secular practice in a number of other non-Christian, or predominantly...

use various base sizes: E17 for C9 bulbs, E12 for C7 bulbs, E10 for decades-old series-wired C6 bulb sets in the U.S., and an entirely different wedge base

Wedge base

for T1¾ mini lights. For a short time early on, these mini lights were manufactured using E5 screw bases.

A tiny E5 or E5.5 size is used only for extra-low voltages, such as in interior illumination

Lighting

Lighting or illumination is the deliberate application of light to achieve some practical or aesthetic effect. Lighting includes the use of both artificial light sources such as lamps and light fixtures, as well as natural illumination by capturing daylight...

for model building

Model building

Model building as a hobby involves the creation of models either from kits or from materials and components acquired by the builder.Categories of modelling include:*Scale model building*Live steam models*Matchstick models*Military models...

s, and model vehicle

Vehicle

A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....

s such as model trains. These are often called "pea

Pea

A pea is most commonly the small spherical seed or the seed-pod of the pod fruit Pisum sativum. Each pod contains several peas. Peapods are botanically a fruit, since they contain seeds developed from the ovary of a flower. However, peas are considered to be a vegetable in cooking...

bulbs" if they are globe-shaped, but they commonly look like mini Christmas bulbs, or large "grain-of-wheat

Wheat

Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

" bulbs. E10 bulbs are common on battery-powered flashlight

Flashlight

A flashlight is a hand-held electric-powered light source. Usually the light source is a small incandescent lightbulb or light-emitting diode...

s, as are bayonet mounts (although those are usually held in with a circular flange

Flange

A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...

located where the base meets the bulb). The E11 base is sometimes used for expensive 50/75/100-watt halogen lights in North America, where it is called the "mini-can", and tighter threads are apparently used to keep them out of E12-base nightlight

Nightlight

A nightlight is a small light fixture, often electrical, placed for comfort or convenience in dark areas or areas that become dark at certain times, such as in an emergency...

s and other places where they could start a fire.

There are also adapters between screw sizes, and for adapting to or from bayonet caps. A socket extender makes the bulb stick out further, such as to accommodate a compact fluorescent lamp

Compact fluorescent lamp

A compact fluorescent lamp , also called compact fluorescent light, energy-saving light, and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent lamp; some types fit into light fixtures formerly used for incandescent lamps...

with a self-ballast

Electrical ballast

An electrical ballast is a device intended to limit the amount of current in an electric circuit. A familiar and widely used example is the inductive ballast used in fluorescent lamps, to limit the current through the tube, which would otherwise rise to destructive levels due to the tube's...

that will not fit in a recessed lighting fixture.

Other uses

Some adapters for wall outlets use an Edison screw, allowing a light socket to become an ungrounded electrical outlet (such as to install Christmas lights temporarily via a porch

Porch

A porch is external to the walls of the main building proper, but may be enclosed by screen, latticework, broad windows, or other light frame walls extending from the main structure.There are various styles of porches, all of which depend on the architectural tradition of its location...

light), or to make a pullchain switch with two outlets, or to split it for two bulbs. Another adapter will make a wall outlet into a light socket.

The Edison screw socket was used as an outlet (such as for toaster

Toaster

The toaster is typically a small electric kitchen appliance designed to toast multiple types of bread products. A typical modern two-slice toaster draws anywhere between 600 and 1200 W and makes toast in 1 to 3 minutes...

s) when mains electricity

Mains electricity

Mains is the general-purpose alternating current electric power supply. In the US, electric power is referred to by several names including household power, household electricity, powerline, domestic power, wall power, line power, AC power, city power, street power, and grid power...

was still mainly used for lighting

Lighting

, and before wall outlets became common. Various other accessories have been made, including a smoke detector

Smoke detector

A smoke detector is a device that detects smoke, typically as an indicator of fire. Commercial, industrial, and mass residential devices issue a signal to a fire alarm system, while household detectors, known as smoke alarms, generally issue a local audible and/or visual alarm from the detector...

that recharges

Rechargeable battery

A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to...

over a few hours and lasts for a few days or weeks thereafter, and still allows the attached bulb to operate normally. There have also been electronics that stick onto the end of the screw base and will allow the attached bulb to flash, for example, to attract the attention of arriving guests or emergency vehicle

Emergency vehicle

An emergency vehicle is any vehicle that is designated and authorized to respond to an emergency. These vehicles are usually operated by designated agencies, often part of the government, but also run by charities, non-governmental organizations and some commercial companies...

s; others function as a dimmer

Dimmer

Dimmers are devices used to vary the brightness of a light. By decreasing or increasing the RMS voltage and, hence, the mean power to the lamp, it is possible to vary the intensity of the light output...

or timer

Timer

A timer is a specialized type of clock. A timer can be used to control the sequence of an event or process. Whereas a stopwatch counts upwards from zero for measuring elapsed time, a timer counts down from a specified time interval, like an hourglass.Timers can be mechanical, electromechanical,...

, or dim gradually in a child's bedroom

Bedroom

A bedroom is a private room where people usually sleep for the night or relax during the day.About one third of our lives are spent sleeping and most of the time we are asleep, we are sleeping in a bedroom. To be considered a bedroom the room needs to have bed. Bedrooms can range from really simple...

in the evening.

Edison screw-cap fittings

Designation	Base Diameter (Crest of thread)	Name	IEC International Electrotechnical Commission The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"... 60061-1 standard sheet
	05 mm	Lilliput Edison Screw (LES)	7004-25
E10	10 mm	Miniature Edison Screw (MES)	7004-22
E11	11 mm	Mini-Candelabra Edison Screw (mini-can)	(7004-06-1)
E12	12 mm	Candelabra Edison Screw (CES)	7004-28
E14	14 mm	Small Edison Screw (SES)	7004-23
E17	17 mm	Intermediate Edison Screw (IES)	7004-26
E26	26 mm	[Medium] (one-inch) Edison Screw (ES or MES)	7004-21A-2
E27	27 mm	[Medium] Edison Screw (ES)	7004-21
E29	29 mm	[Admedium] Edison Screw (ES)
E39	39 mm	Single-contact (Mogul) Giant Edison Screw (GES)	7004-24-A1
E40	40 mm	(Mogul) Giant Edison Screw (GES)	7004-24

Three-way bulbs have a d suffix to indicate double contacts, usually E26d or E27d, or rarely E39d. The second contact is used for the lower-wattage filament of the two inside the bulb. This extra contact is a ring located around the main contact. Unlike bayonet sockets, three-way and regular bulbs are interchangeable, although the low filament or low setting will not work if they are mismatched.

The medium Edison screw has seven threads per inch, or about 3.6mm per thread. In the U.S., the Energy Independence and Security Act of 2007

Energy Independence and Security Act of 2007

The Energy Independence and Security Act of 2007 is an Act of Congress concerning the energy policy of the United States...

requirement for greater energy efficiency

Efficient energy use

Efficient energy use, sometimes simply called energy efficiency, is the goal of efforts to reduce the amount of energy required to provide products and services. For example, insulating a home allows a building to use less heating and cooling energy to achieve and maintain a comfortable temperature...

only applies to the medium Edison screw, all other being considered "specialty" bulbs.

History

Sizes and applications

Other uses

Edison screw-cap fittings

See also