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{{Short description|Holder and connection for electrical lamps}} |
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{{technical|date=December 2011}} |
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{{redirect-distinguish|Lampholder|candle holder (disambiguation)}} |
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[[Light bulbs]] draw their power from wires via electrical/mechanical connections. It is impossible to discuss the sockets without referring to the specifics of the light bulb itself - as the two are intimately connected. The socket is the connector to the electrical power and consists of two parts - the male component attached to the light bulb and the female component attached to the power source via a system of plugs, receptacles, wires, circuit protectors and transformers (for AC sources). |
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{{redirect|Lamp base|bases for lamps|lamp (disambiguation)}} |
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{{more citations needed|date=December 2011}} |
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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 (electrical component)|lamp]] base.<ref>{{cite book|url=https://books.google.com/books?id=3ABCNuipNm0C&q=edison+lamp+socket+GAS+thread&pg=PP755|title=Specifications and Drawings of Patents Relating to Electricity: Issued by the United States...|publisher=U.S. Government Printing Office|year=1882|pages=755–}}</ref> 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.<ref>{{cite web|title=The Advantages of Using LED Verlichting|work=The Difference of Connections|url=http://www.ledgu10dimbaar.nl/website/index.php?TreeItem=391161&NewsItem=28097|publisher=LED Spots & LED Inbouwspots|access-date=16 August 2013|url-status=dead|archive-url=https://archive.today/20130816132543/http://www.ledgu10dimbaar.nl/website/index.php?TreeItem=391161&NewsItem=28097|archive-date=16 August 2013}}</ref> |
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There are many different standards for these sockets, created by ''de facto'' and by various [[standards bodies]]. |
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The most common type of sockets for [[mains electricity]] are [[Edison screw]]s, used in continental Europe and North America, while [[bayonet mount]]s dominate in the [[Commonwealth of Nations|Commonwealth]] countries, except Canada, and in the automotive industry. [[Fluorescent lamps]] typically require a two-pin, unthreaded socket. |
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The construction of a socket defines and limits its intended 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. For many years, Underwriter's Laboratories in the USA has specified that copper switchboard bus bars carry no more than 1000 Amps per square inch and be spaced no less than 1/2 inch away from adjacent conductive surfaces to be UL rated when the power source is 120/208/240 volts.<ref>Electro Controls Wireman's handouts - circa 1974</ref> Similar restrictions exist in sockets - 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, bulb 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. |
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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. |
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Incandescent filaments (the oldest electrical light source) produce light by passing current through a resistive element. The very first such elements successfully designed by Thomas Edison were of carbonized cardboard. This proved to be extremely fragile, and tungsten wire eventually became the standard as the melting point of tungsten was sufficiently high that a "white" light could be produced without the wire melting in normal use. The [[color temperature]] of a normal household light bulb is about 2750° Kelvin, which is a yellowish white. These bulbs last about 1000 hours in normal use. Light bulbs used in projection, photography, film and the television industry emit light at a slightly color temperature of 3200°K - but the expected life is much shorter (25 to 250 hours). Incandescent bulbs are extremely inefficient - only about 5% of the total energy applied produces visible light. The remaining 95% is emitted as infrared heat energy. |
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==History== |
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Light bulb designs are largely determined by the radiated power of the light source. The design must consider the total electrical energy converted to heat. The glass bulb must be far enough from the filament that the glass does not melt. Thus, different light bulb designs have evolved to meet specific needs. Just as the melting point of the glass must be considered so must the materials of the socket. The socket 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 (360°F). The majority of the metal used to make the socket is brass, which is easily formed or stamped into the appropriate shape. 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. (Caution: Never do this with an energized circuit!) |
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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{{clarify|date=October 2018}} used simple wooden receptacles with internal copper strips for lamps on the commercial steamship ''[[SS Columbia (1880)|SS Columbia]]'', the first ship to use electric light bulbs. These sockets included switches, but required bulbs to be mounted upright. |
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The Edison organization developed a screw-base in 1880 which was initially made of wood but later made of [[Plaster|plaster of Paris]].<ref>Robert Friedel, Paul Israel, ''Edison's Electric Light: Biography of an Invention'', Rutgers University Press, 1986, {{ISBN|0-8135-1118-6}}, pp. 169-171</ref> Many competitive designs of lamps and sockets appeared in the early era of incandescent lighting, which often were incompatible with other designs. |
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Socket 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 bulb. Sockets used outdoors or in damp areas often suffer from corrosion which can cause the bulb to "stick" in the socket and attempts to change a bulb can result in breakage of either the bulb or the socket. 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. |
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==Construction and materials== |
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The voltage rating of the circuit has much to do with the life expectancy of the bulb in extreme conditions. Automobiles use low voltage lamps with higher current because a thicker filament wire is more resistant to vibration. |
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The construction of a lampholder socket defines and limits its intended primary use. Ceramic insulation can withstand considerably higher [[operating temperature]]s than bakelite or other plastics. The electrical components and wires must be designed to carry the intended current plus a safety factor. |
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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. |
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Improvements in light bulb design such as the quartz bulb and the use of halide or [[halogen]] elements solve some problems but introduce others. Quartz can withstand considerably higher temperatures than glass, so bulbs can be made smaller. However the strength of a quartz bulb at operating temperature can be reduced by the presence of skin oils deposited when installing the bulb. This can cause the bulb to shatter. Some newer light bulb designs such as the MR16 include a glass UV filter and a glass reflector which combine to make it extremely difficult to actually touch the quartz. Halogen light bulbs add a trace amount of iodine inside the bulb. At operating temperature this vaporizes and ionizes the gases surrounding the filament. The result is that the tungsten boiled off the filament (which would normally coat the inside of the bulb) is returned to the filament. This prolongs the life of the filament. |
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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 {{convert|180|°C|°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. |
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Some types of socket are listed here. |
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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. |
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== "Decorative" and standard screw base ([[Edison screw]]) bulb bases == |
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==Edison screw bases== |
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* Miniature E-11 |
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[[File:Light bulb socket E26 three way.jpg|thumb|upright|A standard American three-way lightbulb socket]] |
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* Candelabra E-12 |
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{{Main|Edison screw#Types}} |
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* European E-14 |
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* E10s Miniature (Flashlight lamp) |
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* Intermediate E-17 |
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* E11s Mini-Candelabra |
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* Medium E-26 (This is what Americans call a "normal" lightbulb) |
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* E12s Candelabra |
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* 3-Lite (modified mogul socket with additional ring contact for 3 way bulbs) |
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* E14s European |
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* Mogul E-40 |
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* E17s Intermediate |
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* E26s Medium |
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* E26d [[3-way_lamp|Three-way]] Medium (modified socket with additional ring contact for 3-way lamps) |
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* E27s European |
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* E39s Mogul |
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* E39d Three-way Mogul (modified socket with additional ring contact for 3-way lamps) |
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* E40s European |
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* Skirted (PAR-38) |
* Skirted (PAR-38) |
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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". |
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== Bayonet styles == |
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* Miniature bayonet |
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* Bayonet candelabra |
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* Bayonet Candelabra with prefocusing collar |
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* Medium prefocus |
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* Mogul prefocus |
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== |
==Bi-post== |
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{{main|Bi-pin connector}} |
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The Bi-post base has several advantages |
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[[File:General Electric MS25015-2 1200w 115v airway beacon light bulb left.jpg |thumb|115-volt airway beacon light bulb with a Mogul bi-post base]] |
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*Bulb orientation is fixed so filament will always be in the focal plane. Filament configurations such as the C13D (coiled, zig-zagged) emit far more light perpendicular to the zig zag than parallel to it. |
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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. |
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*Sockets |
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*Mogul bi-post (G38) can handle up to 100 amps and is used with searchlights and film & stage lighting fixtures of 1000 watts or larger. Incandescent, halogen and HMI light sources use this design. |
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*Medium bi-post (G22) is used with film & stage lighting fixtures between 250 and 1000 watts. |
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*Mini bi-post (G4-G6) |
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Common types: |
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*Mogul Bi-post can handle up to 100 Amps and is used with searchlights, film & stage lighting fixtures 1000 watts or larger. Incandescent, halogen and HMI light sources all use this design. |
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*G4 – {{cvt|4|mm|in|5}} pin spacing |
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*Medium Bi-post is used with film & stage lighting fixtures between 250 and 1000 watts (the development of the T14 base up to horizon design for ellipsoidal spotlights was one of the most important innovations of the mid 20th century) |
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**<small>GU4 & GZ4 – same as G4 and only denote what lamp mount clip is needed to hold the actual light bulb in place</small> |
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*Mini Bi-post |
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*G5.3 – {{cvt|5.3|mm|in|5}} pin spacing |
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<gallery> |
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**<small>GU5.3, GX5.3, GY5.3, GZ5.3 – same as G5.3 and only denote what lamp mount clip is needed to hold the actual light bulb in place</small> |
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File:Example.jpg|Burnt out 1000 watt quartz halogen light bulb with mogul bi-post base. Note bulge on left side of bulb where heat from filament softened quartz and caused outgassing that resulted in filament failure when exposed to oxygen. |
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*G6.35 – {{cvt|6.35|mm|in|2}}spacing |
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</gallery> |
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**<small>GY6.35 & GZ6.35 – same as G6.35 and only denote what lamp mount clip is needed to hold the actual light bulb in place</small> |
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*G8 – {{cvt|8|mm|in|5}} pin spacing |
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**<small>GU8 – same as G8 and only denotes what lamp mount clip is needed to hold the actual light bulb in place</small> |
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*GY8.6 – {{cvt|8.6|mm|in|5}} pin spacing |
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*G9 – {{cvt|9|mm|in|5}} pin spacing |
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*G12 – {{cvt|12|mm|in|5}} pin spacing |
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== Bi |
== Bi-pin connector == |
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{{Unreferenced section|date=May 2017}} |
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[[Image:Halogenmetalldampflampe.jpg|thumb| [[Metal halide lamp]] with G8.5 base ]] |
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{{main|Bi-pin connector}} |
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* Medium bi-pin is used on each end of a T12 fluorescent lamp |
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* Mini bi-pin is used with MR16 halogen lamps |
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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 lamp|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 [[projector]]s, which defines the exact positioning of the filament on one side. This improves the "point source" characteristic necessary for building complex optical systems. |
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*Medium bi-pin is used on each end of a T12 florescent bulb |
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*mini bi-pin is used with MR16 halogen bulbs |
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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. |
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== Two Pin == |
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The 2 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 2 pin base halogen lamp allows designers to insert the bulb into the end of the ellipsoidal reflector through a smaller hole than previously possible with conventional incandescent bulbs. This improves efficiency compared to the older side inserted bulb or a double ended bulb which requires two holes. One variation is the Polarized 2 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. |
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==Bayonet styles== |
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Another facet of the two pin design is that many new designs of bulbs use baseless glass envelopes. The wire leads are thickened and crimped in the glass envelope of the bulb base. The MR16 is an example of this design. You may argue that the reflector itself is the base, but the industry has decided that the reflector is an assembly where the actual bulb is inserted into the reflector with the leads sticking out and a ceramic paste used to glue it in. |
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[[File:Bayonet-mount-01.svg|thumb|upright|A bayonet mount]] |
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{{main|Bayonet mount}} |
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== fluorescent tube standards == |
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* BA9s Miniature bayonet |
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* B15s Single Contact Bayonet |
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* B15d Double Contact Bayonet |
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* BA15d Indexed DC Bayonet |
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* B22d Double Contact Bayonet – the standard "BC" (bayonet cap) used for domestic lighting in the UK and other Commonwealth countries. |
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* Bayonet Candelabra with prefocusing collar |
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* P28s Medium prefocus |
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* P40s Mogul prefocus |
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==Wedge base== |
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* T-5 mini |
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{{main|Wedge base}} |
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* T-8 medium |
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[[Image:Incandescent_Architectural_Strip_Lamp,_showing_S14s_connection.jpg|thumb|Architectural strip lamp with S14s connection]] |
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* T-12 large |
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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. |
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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. |
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== Specialty == |
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==Fluorescent tubular lamp == |
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* Medium |
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{{main|Fluorescent-lamp formats}}Fluorescent Linear Tube Light bulbs are measured in {{frac|1|8}} of inches. So a T12 fluorescent is {{frac|12|8}} of an inch in diameter or {{frac|12|8}} = 1.50" |
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* Three Contact Medium 3C Med |
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* T4 – 4/8 or {{cvt|0.500|in|mm|1}} in diameter |
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* ... |
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* T5 – 5/8 or {{cvt|0.625|in|mm|3}} in diameter |
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* T8 – 8/8 or {{cvt|1.00|in|mm|1}} in diameter |
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* T10 – 10/8 or {{cvt|1.25|in|mm|2}} in diameter |
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* T12 – 12/8 or {{cvt|1.5|in|mm|1}} in diameter |
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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 lamp]]s. |
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== [[Phillips]] Compact Fluorescent types == |
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==Lamp base styles== |
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* G-23 |
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* GX23 |
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* GX32d-2 |
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* GX32d-3 |
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* ... |
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== [[ General Electric ]] Compact Fluorescent types == |
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*... |
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*... |
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== SLI Compact Fluorescent types == |
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*... |
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*... |
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== Design and Use Terms == |
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As light bulbs are designed to meet specific needs from general illumination to precision control of the light emitted, lightbulb sockets must be designed and chosen based on the needs of the application.<ref>1990 Lampholders catalog from GTE Sylvania Emmissive Products</ref> |
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=== Large Lamp Base Styles === |
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{| class="wikitable" |
{| class="wikitable" |
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| Line 97: | Line 112: | ||
| Cand || Candelabra |
| Cand || Candelabra |
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|- |
|- |
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| |
| DCB || Double contact bayonet candelabra |
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|- |
|- |
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| DC Pf || Double contact prefocus candelabra |
| DC Pf || Double contact prefocus candelabra |
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| Line 105: | Line 120: | ||
| F || Ferrule contact |
| F || Ferrule contact |
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|- |
|- |
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| Mc || |
| Mc || Minican |
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|- |
|- |
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| Med || Medium |
| Med || Medium |
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| Line 131: | Line 146: | ||
| G38 Bp || G38 mogul bipost |
| G38 Bp || G38 mogul bipost |
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|- |
|- |
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| R7S || Also known as a double ended [[halogen lamp]]. Mainly used with linear halogen lamps measuring 118mm or 78mm. |
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| Rect RSC || rectangular recessed single contact |
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|- |
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| Rect RSC || Rectangular recessed single contact |
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|- |
|- |
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| RM2P || Rim mount two pin |
| RM2P || Rim mount two pin |
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| Line 167: | Line 184: | ||
| 3P || Three prong |
| 3P || Three prong |
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|} |
|} |
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Some of |
Some of the above base styles are now obsolete. The trend in recent years{{When|date=August 2013}} has been to design newer bases to reduce waste of raw materials and simplify the replacement process. |
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==Standards== |
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=== Bulb Dimensions === |
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{| class="wikitable" |
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|- |
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! Abbreviation !! Term |
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|- |
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|LL || Light length (filament length) |
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|- |
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|LCL || Light center length (optical center of the filament) |
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|- |
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|C-to-C || Contact to contact |
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|- |
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|MOL || Maximum overall length |
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|- |
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|Dia || Diameter |
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|- |
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|Max || Maximum |
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|} |
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If the socket design dimensions are known it is easy to calculate how high the LCL of the bulb will be above the base of the socket. The MOL of the bulb plus the seated height of the bottom of the base will help determine the size of a container for the finished lighting fixture. |
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[[International Electrotechnical Commission]] (IEC) |
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=== Common Burn Positions === |
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* IEC 60061-1, ''Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 1: Lamp caps''<ref name="IEC">{{cite web |url=https://webstore.iec.ch/preview/info_iec60061%7Bed1.0%7Db.pdf |title=IEC 60061 - Lamp caps and holders |date= 2020-11-30 |publisher=International Electrotechnical Commission |access-date=2021-03-22}}</ref> |
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{| class="wikitable" |
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* IEC 60061-2, ''Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 2: Lampholders''<ref name="IEC" /> |
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|- |
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* IEC 60061-3, ''Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 3: Gauges''<ref name="IEC" /> |
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! Abbreviation !! Term |
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* IEC 60061-4, ''Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 4: Guidelines and general information''<ref name="IEC" /> |
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|- |
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| BD || Base down |
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|- |
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| BD/45 || Within 45 degrees of vertical base down |
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|- |
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| BD/Hor || Base down to horizontal |
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|- |
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| BU || Base up |
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|- |
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| Horiz || Horizontal |
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|- |
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| Univ || Universal |
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|} |
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Examples using conventional incandescent bulbs (all require ceramic high temperature sockets and wiring): <ref>IES Lighting Handbook Second Edition (1952) (Illuminating Engineering Society) </ref> |
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*A 1000 watt PS-52 (Pear Shaped - 52/8 = 6.5" maximum diameter) bulb is designed for universal base orientation. The long neck keeps the base cool enough in any position that solder on the base will not melt. |
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*A 500 watt G-40 (Globe - 40/8 = 5" maximum diameter) bulb is specified as BD/Hor in order to keep the base below the highest part of the bulb so solder on the base will not melt. |
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* A 750 watt T-12 (Tubular - 12/8 = 1.5" maximum diameter) bulb designed for BU use in ellipsoidal spotlights moves the filament to the lowest end of the glass bulb, creating the necessary distance to the base for cooling while having a small diameter so it can be inserted into an ellipsoidal reflector in such a way as to make the reflector more efficient. |
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Contemporary lightbulb construction for lower wattage (15 to 100watts) bulbs rarely uses solder to connect the bulb wire leads to the base. Instead the connection is spot welded. This allows the base to be made from aluminum rather than brass and keeps the cost down. |
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The United States standards for lamp sockets are published by [[ANSI]] and developed by [[NEMA]], are generally harmonized with the relevant [[International Electrotechnical Commission|IEC]] standards and include:<ref name=":0">{{Cite web|url=https://www.nema.org/Standards/ComplimentaryDocuments/C81-64-2005-R2014-Contents-and-Scope.pdf|title=American National Standard for Guidelines and General Information for Electric Lamp Bases, Lampholders, and Gauges|website=www.nema.org|access-date=2018-12-10}}</ref> |
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== References == |
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* ANSI_IEC C78.81, American National Standard For Electric Lamps—Doublecapped Fluorescent Lamps-Dimensional and Electrical Characteristics |
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* ANSI_IEC C81.61, ''American National Standard for Electrical Lamp Bases - Specifications for Bases (Caps) for Electric Lamps'' |
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* ANSI_IEC C81.62, ''American National Standard for Electric Lampholders'' |
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* ANSI_IEC C81.63, ''American National Standard for Gauges for Electric Lamp Bases and Lampholders'' |
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* ANSI C81.64, ''American National Standard for Guidelines and General Information for Electric Lamp Bases, Lampholders, and Gauges<ref name=":0" />'' |
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== See also == |
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* [[List of automotive light bulb types]] |
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==References== |
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<references /> |
<references /> |
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* http://www.goodmart.com/info/base_general.aspx |
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== External links == |
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* http://www.lightbulbsdirect.com/page/001/CTGY/Base |
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* {{Commons category-inline |Lampholder sockets}} |
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*http://www.gelighting.com/na/business_lighting/education_resources/literature_library/catalogs/downloads/Lighting_and_Ballasts_Section_D_Appendix_and_Glossary.pdf |
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{{Artificial light sources}} |
{{Artificial light sources}} |
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{{Electronic components}} |
{{Electronic components}} |
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[[Category:Electrical standards]] |
[[Category:Electrical standards]] |
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[[Category: |
[[Category:Types of lamp]] |
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[[Category:Electrical power connectors]] |
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{{Measurement-stub}} |
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Latest revision as of 21:41, 18 September 2024
 | This article needs additional citations for verification. (December 2011) |
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]
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
[edit]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
[edit]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
[edit]
- E10s Miniature (Flashlight lamp)
- E11s Mini-Candelabra
- E12s Candelabra
- E14s European
- E17s Intermediate
- E26s Medium
- E26d Three-way Medium (modified socket with additional ring contact for 3-way lamps)
- E27s European
- E39s Mogul
- E39d Three-way Mogul (modified socket with additional ring contact for 3-way lamps)
- E40s European
- Skirted (PAR-38)
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
[edit]
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.
- Mogul bi-post (G38) can handle up to 100 amps and is used with searchlights and film & stage lighting fixtures of 1000 watts or larger. Incandescent, halogen and HMI light sources use this design.
- Medium bi-post (G22) is used with film & stage lighting fixtures between 250 and 1000 watts.
- Mini bi-post (G4-G6)
Common types:
- G4 – 4 mm (0.15748 in) pin spacing
- GU4 & GZ4 – same as G4 and only denote what lamp mount clip is needed to hold the actual light bulb in place
- G5.3 – 5.3 mm (0.20866 in) pin spacing
- GU5.3, GX5.3, GY5.3, GZ5.3 – same as G5.3 and only denote what lamp mount clip is needed to hold the actual light bulb in place
- G6.35 – 6.35 mm (0.25 in)spacing
- GY6.35 & GZ6.35 – same as G6.35 and only denote what lamp mount clip is needed to hold the actual light bulb in place
- G8 – 8 mm (0.31496 in) pin spacing
- GU8 – same as G8 and only denotes what lamp mount clip is needed to hold the actual light bulb in place
- GY8.6 – 8.6 mm (0.33858 in) pin spacing
- G9 – 9 mm (0.35433 in) pin spacing
- G12 – 12 mm (0.47244 in) pin spacing
Bi-pin connector
[edit] |
- Medium bi-pin is used on each end of a T12 fluorescent lamp
- Mini bi-pin is used with MR16 halogen lamps
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
[edit]
- BA9s Miniature bayonet
- B15s Single Contact Bayonet
- B15d Double Contact Bayonet
- BA15d Indexed DC Bayonet
- B22d Double Contact Bayonet – the standard "BC" (bayonet cap) used for domestic lighting in the UK and other Commonwealth countries.
- Bayonet Candelabra with prefocusing collar
- P28s Medium prefocus
- P40s Mogul prefocus
Wedge base
[edit]
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
[edit]Fluorescent Linear Tube Light bulbs are measured in 1⁄8 of inches. So a T12 fluorescent is 12⁄8 of an inch in diameter or 12⁄8 = 1.50"
- T4 – 4/8 or 0.500 in (12.7 mm) in diameter
- T5 – 5/8 or 0.625 in (15.875 mm) in diameter
- T8 – 8/8 or 1.00 in (25.4 mm) in diameter
- T10 – 10/8 or 1.25 in (31.75 mm) in diameter
- T12 – 12/8 or 1.5 in (38.1 mm) in diameter
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
[edit]| Abbreviation | Term |
|---|---|
| Cand | Candelabra |
| DCB | Double contact bayonet candelabra |
| DC Pf | Double contact prefocus candelabra |
| EMEP | Extended mogul end prong ferrule contact |
| F | Ferrule contact |
| Mc | Minican |
| Med | Medium |
| Med Bp | Medium bipost |
| Med Pf | Medium Prefocus |
| Med Skt | Medium Skirted |
| Med 2P | Medium two pin |
| MEP | Mogul End Prong |
| Mog | Mogul |
| Mog Bp | Mogul bipost |
| Mog Pf | Mogul prefocus |
| MS | Miniature screw (with reference shoulder) |
| MSP | Medium side prong |
| G38 Bp | G38 mogul bipost |
| R7S | Also known as a double ended halogen lamp. Mainly used with linear halogen lamps measuring 118mm or 78mm. |
| Rect RSC | Rectangular recessed single contact |
| RM2P | Rim mount two pin |
| RSC | Recessed single contact |
| S | Metal sleeve |
| SC Bay | Single contact bayonet |
| SC Pf | Single contact prefocus |
| SFc 10-4 | Sleeve with threaded pin |
| SFc 15, 5-6 | Sleeve with threaded pin |
| ST | Screw terminal |
| TB2P | TruBeam two pin |
| Tf | Trufocus (also four pin) |
| TLMS | Tru-Loc miniature screw |
| 2B | Two button |
| 2PAG | Two pin all glass |
| 2PAGC | Two pin all glass with ceramic cover |
| 2PM | Two pin miniature |
| 2PP | Two pin prefocus |
| 3P | Three 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
[edit]International Electrotechnical Commission (IEC)
- IEC 60061-1, Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 1: Lamp caps[4]
- IEC 60061-2, Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 2: Lampholders[4]
- IEC 60061-3, Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 3: Gauges[4]
- IEC 60061-4, Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 4: Guidelines and general information[4]
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]
- ANSI_IEC C78.81, American National Standard For Electric Lamps—Doublecapped Fluorescent Lamps-Dimensional and Electrical Characteristics
- ANSI_IEC C81.61, American National Standard for Electrical Lamp Bases - Specifications for Bases (Caps) for Electric Lamps
- ANSI_IEC C81.62, American National Standard for Electric Lampholders
- ANSI_IEC C81.63, American National Standard for Gauges for Electric Lamp Bases and Lampholders
- ANSI C81.64, American National Standard for Guidelines and General Information for Electric Lamp Bases, Lampholders, and Gauges[5]
See also
[edit]References
[edit]- ^ Specifications and Drawings of Patents Relating to Electricity: Issued by the United States... U.S. Government Printing Office. 1882. pp. 755–.
- ^ "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.
- ^ Robert Friedel, Paul Israel, Edison's Electric Light: Biography of an Invention, Rutgers University Press, 1986, ISBN 0-8135-1118-6, pp. 169-171
- ^ a b c d "IEC 60061 - Lamp caps and holders" (PDF). International Electrotechnical Commission. 2020-11-30. Retrieved 2021-03-22.
- ^ a b "American National Standard for Guidelines and General Information for Electric Lamp Bases, Lampholders, and Gauges" (PDF). www.nema.org. Retrieved 2018-12-10.
External links
[edit]
Media related to Lampholder sockets at Wikimedia Commons
