Lightbulb socket

Light bulbs draw their power from wires via electrical/mechanical connections.

There are many different standards for these sockets, created by de facto and by various standards bodies.

Some types of socket are listed here.

"Decorative" and standard (Edison screw) bulb bases

• Mini Candelabara E-11
• Candelabra E-12
• European E-14
• Intermediate E-17
• Medium E-26 (This is what Americans call a "normal" lightbulb)
• Mogul E-40

Bi-Post

The Bi-post base has several advantages

• 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.
• Sockets

• Mogul Bi-post is used with searchlights, film & stage lighting fixtures 1000 watts or larger. Incandescent, halogen and HMI light sources use this design.
• 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)
• Mini Bi-post

Bi Pin

• Medium bi-pin is used on each end of a T12 florescent bulb
• mini bi-pin is used with MR16 halogen bulbs

Two Pin

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 small hole. 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.

fluorescent tube standards

• T-5 mini
• T-8 medium
• T-12 large

Specialty

• Medium Medium
• Three Contact Medium 3C Med
• ...

Phillips Compact Fluorescent types

• G-23
• GX23
• GX32d-2
• GX32d-3
• ...

General Electric Compact Fluorescent types

• ...
• ...

SLI Compact Fluorescent types

• ...
• ...

Design and Use Terms

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.

Bulb Dimensions

Abbreviation	Term
LL	Light length (filament length)
LCL	Light center length
C-to-C	Contact to contact
MOL	Maximum overall length
Dia	Diameter
Max	Maximum

Burn Positions

Abbreviation	Term
BD	Base down
BD/45	Within 45 degrees of vertical base down
BD/Hor	Base down to horizontal
BU	Base up
Horiz	Horizontal
Univ	Universal

Examples:

• A 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.
• A 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.
• A 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.

Contemporary lightbulb construction for pear shaped or A 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.

References

• http://www.goodmart.com/info/base_general.aspx
• http://www.lightbulbsdirect.com/page/001/CTGY/Base
• http://www.gelighting.com/na/business_lighting/education_resources/literature_library/catalogs/downloads/Lighting_and_Ballasts_Section_D_Appendix_and_Glossary.pdf
• IES Handbook (Illuminating Engineering Society)