EDISON SCREW (ES) is a standard socket for light bulbs in the United
States. It was developed by
* 1 History * 2 Types * 3 Other uses * 4 Fittings * 5 See also * 6 Notes * 7 References
Early U.S. lamp manufacturers used different and incompatible bases.
Thomson-Houston Electric Company
In response to Edison's patent ,
Three-way E26d light socket E26
Specifications for all lamp mount types are defined in the following American National Standards Institute (ANSI) and International Electrotechnical Commission (IEC) publications:
* Lamp Caps — ANSI C81.61 and IEC 60061-1 * Lamp Holders — ANSI C81.62 and IEC 60061-2 * Gauges (to ensure interchangeability) — ANSI C81.63 and IEC 60061-3 * Guidelines for Electrical Lamp Bases, Lampholders and Gauges — ANSI C81.64 and IEC 60061-4
Generally, the two standards are harmonized, although several types of screw mount are still defined in only one standard.
In the designation "Exx", "E" stands for "Edison" and "xx" indicates the diameter in millimeters as measured across the peaks of the thread on the base (male), e.g., E12 has a diameter of 12 mm. This is distinct from the bulb glass diameter, which in the U.S. is given in eighths of an inch, e.g., A19, MR16 , T12.
There are four commonly used thread size groups for mains supply lamps:
* Candelabra: E12 North America, E11 in Europe * Intermediate: E17 North America, E14 (Small ES, SES) in Europe * Medium or standard: E26 (MES) in North America, E27 (ES) in Europe * Mogul: E39 North America, E40 (Goliath ES) in Europe.
The E26 and E27 are usually interchangeable, as are the E39 and E40, because there is only a 1 mm difference in thread outside diameter. E11 and E12 are not interchangeable. Other semi-standard screw thread sizes are available for certain specific applications.
The large E39 "Mogul" and E40 "Goliath" base are used on street
lights , and high-wattage lamps (such as a 100-/200-/300-watt
three-way) and many high-intensity discharge bulbs. In areas following
National Electrical Code , general-use lamps over 300 W
cannot use an E26 base and must instead use the E39 base, 300 W lamps
may use either base. Medium
E29 "Admedium" bases are used for special applications, for example UV spotlight bulbs in magnetic crack detection machines.
In countries that use 220–240 volts AC domestic power ,
standard-size E27 and small E14 are the most common screw-mount sizes
and are prevalent throughout continental Europe and
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 fans .
A tiny E5 or E5.5 size is used only for extra-low voltages , such as in interior illumination for model buildings , and model vehicles such as model trains . These are often called "pea bulbs" if they are globe-shaped, but they commonly look like mini Christmas bulbs, or large "grain-of-wheat " bulbs. E10 bulbs are common on battery -powered flashlights , as are bayonet mounts (although those are usually held in with a circular flange located where the base meets the bulb). The E11 base is sometimes used for 50/75/100-watt halogen lights in North America, where it is called the "mini-can", and tighter threads are used to keep them out of E12-base nightlights 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 with a self-ballast that doesn't fit in a recessed lighting fixture.
Most Edison screws have right-hand threads (lamp is turned clockwise
to tighten), but left-hand threaded screws do exist, generally for use
in special cases in which a specific voltage or wattage is required.
This discourages using an incorrect bulb, which could result in an
explosion or other incident. Locations such as railway trains and the
New York City Subway
A 1909 toaster with Edison plug
In North America, fuses were used in buildings wired before 1960. These Edison base fuses would screw into a fuse socket similar to Edison-base incandescent lamps.
Some adapters for wall outlets use an Edison screw, allowing a light
socket to become an ungrounded electrical outlet (such as to install
Various other accessories have been made, including a smoke detector that recharges over a few hours and lasts for a few days or weeks thereafter, and still allows the attached lamp to operate normally. There have also been electronics that stick onto the end of the screw base and allow the attached lamp to flash, for example, to attract the attention of arriving guests or emergency vehicles ; others function as a dimmer or timer , or dim gradually in a child's bedroom in the evening.
Some thermionic valves, such as certain rectifiers, use an Edison screw base.
From left to right: E27, E14, and E10 bulbs
DESIGNATION BASE MAJOR DIAMETER (THREAD EXTERNAL) NAME APPLICATION IEC 60061-1 STANDARD SHEET
E05 !E5 05 mm Lilliput Edison Screw (LES) Indicator lights, decorative lights 7004-25
E10 10 mm Miniature Edison Screw (MES) Flashlights, bicycle lights 7004-22
E11 11 mm Mini-Candelabra Edison Screw (mini-can) 120 V halogen mini-candelabra (7004-06-1)
E12 12 mm Candelabra Edison Screw (CES), C7 120 V candelabra/night lamp 7004-28
E14 14 mm Small Edison Screw (SES) 230 V candelabra/chandelier, night lamps, and some pendant lights. 7004-23
E17 17 mm Intermediate Edison Screw (IES), C9 120 V appliance 7004-26
E26 26 mm (one-inch) Edison Screw (ES or MES) Standard 120 V lamps 7004-21A-2
E27 27 mm Edison Screw (ES) Standard 230 V lamps 7004-21
E29 29 mm Edison Screw (ES)
E39 39 mm Single-contact (Mogul- in America) Goliath Edison Screw (GES) 120 V 250+ W industrial 7004-24-A1
E40 40 mm (Mogul) Goliath Edison Screw (GES) 230 V 250+ W industrial 7004-24
Three-way lamps 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 lamp. This extra contact is a ring located around the main contact. Unlike bayonet sockets, three-way and regular lamps are interchangeable, although the low filament or low setting doesn’t work if mismatched.
Diazed fuses DII uses the same E27 thread as standard 230 V lamps, but have a longer body and cannot be screwed into a lamp holder (socket). A lamp base is too short to contact the bottom terminal of a fuse holder. However it's possible (but not useful) to screw a DII fuse holder without a fuse in an E27 lamp holder.
Screw bases have a number of disadvantages compared to the bayonet fit type:
* 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 live, presenting an electric shock hazard to anyone attempting to change the lamp. * It is possible to over-tighten the screw, risking breaking the bulb or separation of the glass from the metal base and leaving the base in the socket, especially when subsequently attempting to unscrew it. * If the lamp becomes loose in the socket due to vibration or under-tightening, it can lose contact with the center contact and stop working until it is tightened. The bayonet type is resistant to vibration and much less likely to become loose. * As the metal thread carries current, any arcing can jam the thread. * Corrosion is more likely to jam a screw thread than a bayonet fixing. * Screwing in and unscrewing the bulb places more force on the glass envelope.
Screw bases have a number of advantages compared to the bayonet fit type:
* Screw bases are more suitable for small size bulbs * A bulb fully screwed home is more secure than a bayonet fit bulb * Moisture and debris are less likely to contaminate the contacts of a screw base bulb * Spring contacts are not necessary on screw base bulbs (the spring tension must not only ensure a good contact but it must also hold the bulb securely in the bayonet so there is a compromise)
Wikimedia Commons has media related to EDISON SCREW .
* ^ The BC or bayonet mount fitting is the commonest light bulb fitting in the UK and many British Commonwealth countries, and is found in older installations in some other countries, including France and Greece.
* ^ I.C.S. Reference Library volume 4B, International Textbook
Company , Scranton PA 1908, page 43-41
* ^ "Lamp Size Reference". lightopedia.com. Retrieved 2017-04-23.
* ^ "Light Bulb Shape and Size Chart Reference Charts
Bulbs.com". Bulbs.com. Retrieved 2016-07-27.
* ANSI C81.61-2007 American National Standard for electrical lamp bases—Specifications for Bases (Caps) for Electric Lamps, available at www.nema.org, retrieved 2009-01-20
* v * t * e
Discoveries and inventions
List of Edison patents
Thomas A. Edison, Inc.
Edison and Swan Electric Light Company
Edison Gower-Bell Telephone Company of Europe, Ltd.
Edison Illuminating Company
Edison Machine Works
Edison Manufacturing Company
Edison Ore-Milling Company
* Black Maria
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* The Execution of Mary Stuart (1895) * The Kiss (1896) * A Night of Terror (1911)