Lightbulb socket

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A lightbulb socket, lightbulb holder,light socket, lamp socket or lamp holder is a device which mechanically supports and provides electrical connections for a compatible electric lamp base. [1] Sockets allow lamps to be safely and conveniently replaced (re-lamping). There are many different standards for lampholders, including early de facto standards and later standards created by various standards bodies. Many of the later standards conform to a general coding system in which a socket type is designated by a letter or abbreviation followed by a number. [2]

Contents

The most common type of sockets for mains electricity are Edison screws, used in continental Europe and North America, while bayonet mounts dominate in the Commonwealth countries, except Canada, and in the automotive industry. Fluorescent lamps typically require a two-pin, unthreaded socket.

Not all lamps require a socket; for example, some miniature lamps have wire leads suitable for direct connection to screw terminals or other wires, and some reflector lamps provide screw terminals for electrical connections.

History

Early experimental incandescent lamps employed wire leads which had to be connected to screw terminals, but this was inconvenient for commercial use. The Edison organization[ clarification needed ] used simple wooden receptacles with internal copper strips for lamps on the commercial steamship SS Columbia , the first ship to use electric light bulbs. These sockets included switches, but required bulbs to be mounted upright.

The Edison organization developed a screw-base in 1880 which was initially made of wood but later made of plaster of Paris. [3] Many competitive designs of lamps and sockets appeared in the early era of incandescent lighting, which often were incompatible with other designs.

Construction and materials

The construction of a lampholder socket defines and limits its intended primary use. Ceramic insulation can withstand considerably higher operating temperatures than bakelite or other plastics. The electrical components and wires must be designed to carry the intended current plus a safety factor.

The contact surface area, thickness and conductivity of the metal, connection methods and maximum operating temperature must all be considered in the design of a new socket. In addition, mechanical factors such as shape of the socket, fixture mounting and attachment, lamp support, ease of re-lamping and total cost of manufacture must be considered. Sockets designed for ordinary household and industrial use have much more design leeway than those used in precision applications.

The lampholder must be located far enough from the filament that the metals with the lowest melting point will remain solid. Historically this metal was a tin/lead solder whose melting point might be as low as 180 °C (356 °F) Due to the thermal changes from ambient temperature to full operating temperature, the design of a socket must allow for a considerable amount of expansion and contraction. Spring elements are required to accommodate these dimensional changes. However, the temperature at which a metal loses its spring is far below the melting point. This is why some older sockets that no longer work can be restored by prying up the base spring slightly.

Lampholder failures are usually caused by mechanical abuse or by overheating. A socket with a built-in switch is far more likely to fail in normal use as the switch parts wear out. Insulation failures are usually caused by impacts or by difficulty inserting or removing a lamp. Sockets used outdoors or in damp areas often suffer from corrosion which can cause the lamp to "stick" in the socket and attempts to change a lamp can result in breakage of either the lamp or the lampholder. The corrosion is not only environmentally produced but may be a result of the current flowing through the parts when there is appreciable resistance between the parts. Fixtures in such environments may require gaskets or other waterproofing methods to prevent buildup of moisture in the socket area.

Edison screw bases

A standard American three-way lightbulb socket Light bulb socket E26 three way.jpg
A standard American three-way lightbulb socket

The light bulb commonly used since the early 20th century for general-purpose lighting applications, with a pear-like shape and an Edison screw base, is referred to as an "A-series light bulb." This most common general purpose bulb type would be classed as "A19/E26" or the metric version "A60/E27".

Bi-post

115-volt airway beacon light bulb with a Mogul bi-post base General Electric MS25015-2 1200w 115v airway beacon light bulb left.jpg
115-volt airway beacon light bulb with a Mogul bi-post base

With bi-post bases, the lamp orientation is fixed so that the filament will always be in the focal plane. Filament configurations such as the C13D (coiled, zigzagged) emit far more light perpendicular to the zigzag than parallel to it.

Common types:

Bi-pin connector

Metal halide lamp with G8.5 base Halogenmetalldampflampe.jpg
Metal halide lamp with G8.5 base

The two-pin socket is an update of the bi-post design with smaller pins designed to reduce the cost of manufacture. The 1000-watt FEL medium two-pin base halogen lamp allows designers to insert the lamp into the end of the ellipsoidal reflector through a smaller hole than previously possible with conventional incandescent lamps. This improves efficiency compared to the older side-inserted lamp or a double-ended lamp which requires two holes. One variation is the polarized two-pin socket – used primarily in projectors, which defines the exact positioning of the filament on one side. This improves the "point source" characteristic necessary for building complex optical systems.

Another facet of the two-pin design is that many new designs of lamps use baseless glass envelopes. The wire leads are thickened and crimped in the glass envelope of the lamp base. The MR16 is an example of this design; the actual lamp is inserted into the reflector with the leads sticking out and a ceramic paste used to glue it in.

Bayonet styles

A bayonet mount Bayonet-mount-01.svg
A bayonet mount

Wedge base

Architectural strip lamp with S14s connection Incandescent Architectural Strip Lamp, showing S14s connection.jpg
Architectural strip lamp with S14s connection

Miniature lamps may have a wedge base made of glass or plastic. The base may be an extension of the glass envelope of the bulb, with the wire leads of the lamp folded up at the base. Some wedge bases are made of plastic and slipped over the wire leads. A wedge base holds the lamp by spring compression in the socket. The lamp is inserted and removed without twisting. Wedge base lamps are widely used in automotive applications, and many Christmas lights strings use plastic wedge-based bulbs.

Other wedge bases include strip lamps, sometimes called architectural lamps, with S14s connections. These lamps are used in display cabinets or over mirrors and have been widely replaced by LED equivalents.

Fluorescent tubular lamp

Fluorescent Linear Tube Light bulbs are measured in 18 of inches. So a T12 fluorescent is 128 of an inch in diameter or 128 = 1.50"

Linear tubes are usually equipped on both sides with G13 bi-pin socket (T8, T10, T12) or G5 bi-pin socket (T4, T5). Other sockets are used for compact fluorescent lamps.

Lamp base styles

AbbreviationTerm
CandCandelabra
DCBDouble contact bayonet candelabra
DC PfDouble contact prefocus candelabra
EMEPExtended mogul end prong ferrule contact
FFerrule contact
McMinican
MedMedium
Med BpMedium bipost
Med PfMedium Prefocus
Med SktMedium Skirted
Med 2PMedium two pin
MEPMogul End Prong
MogMogul
Mog BpMogul bipost
Mog PfMogul prefocus
MSMiniature screw (with reference shoulder)
MSPMedium side prong
G38 BpG38 mogul bipost
R7SAlso known as a double ended halogen lamp. Mainly used with linear halogen lamps measuring 118mm or 78mm.
Rect RSCRectangular recessed single contact
RM2PRim mount two pin
RSCRecessed single contact
SMetal sleeve
SC BaySingle contact bayonet
SC PfSingle contact prefocus
SFc 10-4Sleeve with threaded pin
SFc 15, 5-6Sleeve with threaded pin
STScrew terminal
TB2PTruBeam two pin
TfTrufocus (also four pin)
TLMSTru-Loc miniature screw
2BTwo button
2PAGTwo pin all glass
2PAGCTwo pin all glass with ceramic cover
2PMTwo pin miniature
2PPTwo pin prefocus
3PThree prong

Some of the above base styles are now obsolete. The trend in recent years[ when? ] has been to design newer bases to reduce waste of raw materials and simplify the replacement process.

Standards

International Electrotechnical Commission (IEC)

The United States standards for lamp sockets are published by ANSI and developed by NEMA, are generally harmonized with the relevant IEC standards and include: [5]

See also

Related Research Articles

<span class="mw-page-title-main">Halogen lamp</span> Incandescent lamp variety

A halogen lamp is an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope that is filled with a mixture of an inert gas and a small amount of a halogen, such as iodine or bromine. The combination of the halogen gas and the tungsten filament produces a halogen-cycle chemical reaction, which redeposits evaporated tungsten on the filament, increasing its life and maintaining the clarity of the envelope. This allows the filament to operate at a higher temperature than a standard incandescent lamp of similar power and operating life; this also produces light with higher luminous efficacy and color temperature. The small size of halogen lamps permits their use in compact optical systems for projectors and illumination. The small glass envelope may be enclosed in a much larger outer glass bulb, which has a lower temperature, protects the inner bulb from contamination, and makes the bulb mechanically more similar to a conventional lamp.

<span class="mw-page-title-main">Fluorescent lamp</span> Lamp using fluorescence to produce light

A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp, but is less efficient than most LED lamps. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. For comparison, the luminous efficiency of an incandescent bulb may only be 16 lumens per watt.

<span class="mw-page-title-main">AC power plugs and sockets</span> Connector used to connect to mains power

AC power plugs and sockets connect devices to mains electricity to supply them with electrical power. A plug is the connector attached to an electrically-operated device, often via a cable. A socket is fixed in place, often on the internal walls of buildings, and is connected to an AC electrical circuit. Inserting the plug into the socket allows the device to draw power from this circuit.

<span class="mw-page-title-main">Tube socket</span> Plug-in vacuum tube holder

Tube sockets are electrical sockets into which vacuum tubes can be plugged, holding them in place and providing terminals, which can be soldered into the circuit, for each of the pins. Sockets are designed to allow tubes to be inserted in only one orientation. They were used in most tube electronic equipment to allow easy removal and replacement. When tube equipment was common, retailers such as drug stores had vacuum tube testers, and sold replacement tubes. Some Nixie tubes were also designed to use sockets.

<span class="mw-page-title-main">Compact fluorescent lamp</span> Fluorescent lamps with folded tubes, often with built-in ballast

A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for incandescent bulbs. The lamps use a tube that is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.

<span class="mw-page-title-main">Light fixture</span> Electrical device with an electric lamp

A light fixture, light fitting, or luminaire is an electrical lighting device containing one or more light sources, such as lamps, and all the accessory components required for its operation to provide illumination to the environment. All light fixtures have a fixture body and one or more lamps. The lamps may be in sockets for easy replacement—or, in the case of some LED fixtures, hard-wired in place.

<span class="mw-page-title-main">Bayonet mount</span> Fastening mechanism

A bayonet mount or bayonet connector is a fastening mechanism consisting of a cylindrical male side with one or more radial pins, and a female receptor with matching L-shaped slot(s) and with spring(s) to keep the two parts locked together. The slots are shaped like a capital letter L with serif ; the pin slides into the vertical arm of the L, rotates across the horizontal arm, then is pushed slightly upwards into the short vertical "serif" by the spring; the connector is no longer free to rotate unless pushed down against the spring until the pin is out of the "serif".

<span class="mw-page-title-main">Edison screw</span> Lightbulb socket standard (E5-E40)

Edison screw (ES) is a standard lightbulb socket for electric light bulbs. It was developed by Thomas Edison (1847–1931), patented in 1881, and was licensed in 1909 under General Electric's Mazda trademark. The bulbs have right-hand threaded metal bases (caps) which screw into matching threaded sockets. For bulbs powered by AC current, the thread is generally connected to neutral and the contact on the bottom tip of the base is connected to the "live" phase.

<span class="mw-page-title-main">Multifaceted reflector</span> Light bulb

A multifaceted reflector light bulb is a reflector housing format for halogen as well as some LED and fluorescent lamps. MR lamps were originally designed for use in slide projectors, but see use in residential lighting and retail lighting as well. They are suited to applications that require directional lighting such as track lighting, recessed ceiling lights, desk lamps, pendant fixtures, landscape lighting, retail display lighting, and bicycle headlights. MR lamps are designated by symbols such as MR16 where the diameter is represented by numerals indicating units of eighths of an inch. Common sizes for general lighting are MR16 and MR11, with MR20 and MR8 used in specialty applications. Many run on low voltage rather than mains voltage alternating current so require a power supply.

<span class="mw-page-title-main">Bi-pin lamp base</span> Type of lamp/lightbulb fitting/connector

A bipin or bi-pin is a type of lamp fitting. They are included in the IEC standard "IEC 60061 Lamp caps and holders together with gauges for the control of interchangeability and safety". They are used on many small incandescent light bulbs, and for starters on some types of fluorescent lights.

<span class="mw-page-title-main">Holiday lighting technology</span> Decorative lighting for festivities

Holiday lighting technology has been subject to considerable development and variation since the replacement of candles by electric lights. While originally used during the Christmas holidays as Christmas lights, modern electric light arrays have become popular around the world in many cultures and are used both during religious festivals and for other purposes unconnected to any festivities.

<span class="mw-page-title-main">Wedge base</span> Type of electrical mount

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. The wires are usually inserted into a plastic base that the bulb is mounted in, and which is often narrower at the tip than at the bulb, giving it a wedge shape and usually ensuring a tight connection, depending on manufacturing tolerances. Some bulbs have no plastic base, and the wires are simply bent up to the sides of the bulb's glass base.

<span class="mw-page-title-main">Fluorescent-lamp formats</span> Types of lamp

Since their introduction as a commercial product in 1939, many different types of fluorescent lamp have been introduced. Systematic nomenclature identifies mass-market lamps as to overall shape, power rating, length, color, and other electrical and illuminating characteristics.

A 3-way lamp, also known as a tri-light, is a lamp that uses a 3-way light bulb to produce three levels of light in a low-medium-high configuration. A 3-way lamp requires a 3-way bulb and socket, and a 3-way switch.

<span class="mw-page-title-main">A-series light bulb</span> Common light bulb shape

The A-series light bulb is the "classic" glass light bulb shape that has been the most commonly used type for general lighting service (GLS) applications since the early 20th century. It has a pear-like shape and is typically fitted to either an Edison screw or a bayonet cap base. The number that follows the "A" designation indicates the nominal major diameter of the bulb, either in one-eighth inch units in North America or in millimeters in the rest of the world.

<span class="mw-page-title-main">GU24 lamp fitting</span>

A GU24 lamp fitting is a bi-pin connector for compact fluorescent lamps (CFL) or LED lamps that uses a bayonet mount–like twist-lock bi-pin connector instead of the Edison screw fitting used on many CFLs, LED lamps and incandescent light bulbs. The design was initiated by the U.S. EPA and the Lighting Research Center in 2004, in order to facilitate the deployment of compact fluorescent light bulbs with replaceable ballasts.

<span class="mw-page-title-main">AC power plugs and sockets: British and related types</span> AC power plug type

Plugs and sockets for electrical appliances not hardwired to mains electricity originated in the United Kingdom in the 1870s and were initially two-pin designs. These were usually sold as a mating pair, but gradually de facto and then official standards arose to enable the interchange of compatible devices. British standards have proliferated throughout large parts of the former British Empire.

There are approximately 20 types in common use around the world, such as AC power plugs and sockets, and many obsolete socket types which are still found in older buildings.

References

  1. Specifications and Drawings of Patents Relating to Electricity: Issued by the United States... U.S. Government Printing Office. 1882. pp. 755–.
  2. "The Advantages of Using LED Verlichting". The Difference of Connections. LED Spots & LED Inbouwspots. Archived from the original on 16 August 2013. Retrieved 16 August 2013.
  3. Robert Friedel, Paul Israel, Edison's Electric Light: Biography of an Invention, Rutgers University Press, 1986, ISBN   0-8135-1118-6, pp. 169-171
  4. 1 2 3 4 "IEC 60061 - Lamp caps and holders" (PDF). International Electrotechnical Commission. 2020-11-30. Retrieved 2021-03-22.
  5. 1 2 "American National Standard for Guidelines and General Information for Electric Lamp Bases, Lampholders, and Gauges" (PDF). www.nema.org. Retrieved 2018-12-10.