Edison base (EC) is a standard socket for light bulbs. It was designed by Thomas Edison and licensed in 1909 under the Mazda trademark. Lamps are usually right hand threaded metal bases (caps) that fit into the corresponding threaded sockets (lamp holders). For AC powered luminaires, the filament is connected to neutral and the contact at the lower end of the base is connected to the mains.
Content
- Origin story
- Base / plinth types
- Other uses
- Application in devices
Origin story
Early lamp manufacturers in the United States used different and incompatible bases. The Thomson-Houston Electric Company used a threaded stud at the bottom of the socket and a flat slip ring. A Sawyer-Mann or Westinghouse base used a spring clip acting on grooves at the base of the bulb and a pin at the bottom. By about 1908, the Edison base was most widespread in the United States, and the rest began to disappear from use.
In response to Edison's patent, Reginald Fessenden invented two-pin connector for the 1893 World's Fair. Other base / plinth bases include a bayonet base and a wedge base.
In much of the world, Edison screws have supplanted other types of general lighting jacks. In the early days of electrification Edison's screws were the only standard connector, and the fixtures were connected to AC power via light connectors. Today Edison screw connectors meet international standards.
Base / plinth types
Specifications (edit) for all types of fastening are defined in the following American National Standards Institute (ANSI) and International Electrotechnical Commission (IEC) publications:
- Caps - ANSI C81.61 and IEC 60061-1.
- Holders - ANSI C81.62 and IEC 60061-2.
- Sensors (for interchangeability) - ANSI C81.63 and IEC 60061-3.
- Guidelines for Electric Light Beams, Fluorescent Lamps and Sensors are ANSI C81.64 and IEC 60061-4.
Generally, these two standards are harmonized, although several types of screw fastening are still defined. in only one standard. In the notation "Exx", "E" stands for "Edison" and "xx" indicates the diameter in millimeters, measured from the peaks of the threads on the base, for example, E12 has a diameter of 12 mm.
There are four commonly used lamp base size groups:
- Candelabra: E12 North America, E11 in Europe.
- Intermediate: E17 North America, E14 (or Mignon base, 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 base E26 and E27 are usually interchangeable, as are the E39 and E40, since the difference in thread diameter is only 1 mm. E11 and E12 are not interchangeable. Other semi-standard threads are available for some specific applications.
Large base E39 "Mogul" and E40 "Goliath" used in street lamps and high-power luminaires (for example, in three-phase mode at 100/300/300 W). In areas following the NEC, general purpose luminaires greater than 300 watts may not use an E26 base and must use an E39 base instead, 300W units can use any of them.
Luminaires of medium size (MES) for 12 V are also available for vehicles. Previously, emergency exit signs were also used intermediate basebut US and Canadian regulations now require durable and energy efficient LEDs. Medium screw bases must not be able to handle more than 25 amperes.
E29 "Admedium" bases are used for special applicationseg for UV lamps. In countries that use 220-240 volts AC for domestic use, the standard e27 base and small e14 base - the most common sizes of screw fasteners, they are common throughout continental Europe and China.
In 120-volt North America, 100-volt Japan and Taiwan, the standard size for general-purpose luminaires is E26. E12 is commonly used to make a chandelier. E17 is also sometimes used, in small table lamps, and sometimes in newer ceiling fans. Christmas lights use different base sizes E17 for C9 bulbs, E12 for C7 bulbs, E10 for US multi-year serial C6 bulb kits and a completely different wedge base for T13 / 4 mini fixtures. Within a short time, these mini luminaires were manufactured using E5 screw bases.
The tiny size E5 or E5.5 is only used for extra low voltages such as interior lighting for buildings, and model vehicles such as model trains. They are often called "pea bulbs" because they are globe-shaped, but they usually resemble mini Christmas bulbs or large "grain wheat" bulbs.
E10 bulbs are common for battery powered flashlights, as are bayonet mounts (although they are usually held with a circular flange located where the base matches the bulb). The E11 base is sometimes used for 50/75/100 W halogen fixtures in North America, where it is called "mini-cans".
Most Edison screws have right hand threads (the lamp turns clockwise to tighten), but screws are sometimes used left-handed, usually for non-standard voltage or power. This prevents the wrong lamp from being used, which could result in damage. Public places such as train stations and subways use left-handed light bulbs to discourage theft of lamps for use in conventional lighting fixtures.
Other uses
An Edison screw socket was used as an outlet (e.g. for toasters) when electrical grids were still used primarily for lighting, and before mains outlets became common occurrence.
In North America, fuses were used in buildings connected before 1960. These basic Edison fuses were screwed into a fuse slot similar to Edison incandescent bulbs.
Some wall outlet adapters use an Edison screw to allow the outlet to become ungrounded (for example, to installing Christmas lights temporarily across the porch) or to create a switch with two outputs or to open it to two lamps. Another adapter can make a wall socket into a lamp holder (lamp socket).
Various other accessories, including a smoke detector that charges over hours and lasts for days or weeks after that, and still allows the connected bulb to work properly. There was also electronics that adhered to the end of the base of the propeller and allowed the raised lamp to blink, for example, to attract the attention of arriving guests or emergency vehicles.
Application in devices
Three-phase lamps have a d suffix to indicate double contacts, usually E26d or E27d, rarely E39d. The second contact is used for the lower filament inside the device. This auxiliary contact is a ring located around the main contact. Unlike bayonet sockets, 3-way and conventional bulbs are interchangeable.
The small Edison screw has nine threads per inch, or about 2.8mm per thread. The middle Edison screw has seven threads per inch, or about 3.6mm per thread. In the US, the Energy Independence and Security Act of 2007 to improve energy efficiency applies only to the middle Edison propeller, all others are considered "special" lamps.
DII diameter probe fuses use the same E27 thread as standard 230V lamps, but have a longer body and cannot be screwed into the lamp holder (socket). The base of the lamp is too short to contact the lower terminal of the fuse holder. However, it is possible to screw a fuse holder DII without a fuse into a lamp holder such as an E27 base.
A number of disadvantages of the screw base compared to the bayonet mount:
- The metal screw itself forms one of the contacts for the circuit. If the lighting system is not properly connected or the lamp is connected to a non-polarized socket, the metal screw may become mobile, presenting a risk of electric shock to anyone trying to replace lamp.
- Overtightening the screw may be possible, risking breaking the lamp or separating the glass from the metal base and leaving the base in the socket, especially if you later try to unscrew it.
- If the lamp loosens at the outlet due to vibration or pull-up, it may lose contact with the center pin and stop working until it is tightened. The bayonet type is vibration-resistant and is much less likely to become free.
- Since metal threads carry current, any arc can jam the thread.
- Screwing in and unscrewing the lamp puts more force on the glass envelope.
- If you fix something with a cable connected, it will twist when you turn the screw.
Several advantages of these bases:
- Screw bases are more suitable for small lamps.
- A fully screwed light bulb into the house is more reliable than a bayonet type light bulb.
- Moisture and debris are less prone to contact with the screw base.
- Spring contacts are not needed on screw base lamps (the tension on the spring should not only ensure good contact, but should also hold the lamp securely in the bayonet).
The types of lamp caps are constantly being improved. When buying a lamp or choosing a light bulb for it, you need to pay attention to the base used in the lamp.
