Candela

The base is the end of the lamp that fits into the receptacle connected to the electrical supply. Bases provide electrical contact to the lamp and, in most cases, also support the lamp in the fixture. There are many types of bases used in lamps, screw bases being the most common for incandescent and HID lamps, while bipin bases are common for linear fluorescent lamps.

Large Lamp Bases

Here is a list of some common base types for large lamps.

• Incandescent
• Medium
• Mogul
• Candelabra
• Intermediate
• DC Bayonet
• Screw Terminal
• Disc
• Medium Side Prong
• 3 Prong
• Halogen
• Medium
• Medium Skirt
• Medium Nickle Plated
• Mogul
• GX5.3
• GU5.3
• G4
• GY6.35
• Mini Candelabra
• DC Bayonet
• R7s
• Screw Terminal
• Fluorescent
• Medium Bi-Pin
• Miniature Bi-Pin
• Mogul Bi-Pin
• Recessed Double Contact
• Single Pin
• High Intensity Discharge (HID)
• Medium
• Medium Skirt
• Medium Nickle Plated
• Mogul
• G8.5
• G12
• GU6.5
• GX10
• PGJ5
• PGZ18
• RX7s
• Compact Fluorescent
• Medium
• G23-2
• G24d-1
• G24d-2
• G24d-3
• 2G11-4
• G24q-1
• G24q-2
• G24q-3
• GR8-2
• GR10q-3

Miniature Bases

For miniature and subminiature lamps, bayonet or wedge base types are generally preferred over screw types when vibration is present. In addition, wedge bases reduce socket size and complexity. Flanged or collared types are usually associated with requirements for filament location.

The shape of a bulb is identified by a letter or letters followed by its maximum diameter, expressed in eighths of an inch. For example, a R40 has a maximum diameter of 40 eighths of an inch which equals 5 inches.

Various bulb shapes are as follows:

The general term applied to fluorescent lamps that are single-ended and that have smaller diameter tubes that are bent to form a compact shape. Some CFLs have integral ballasts and medium or candelabra screw bases for easy replacement of incandescent lamps.

The wire inside an incandescent lamp envelope that glows and emits light when heated, i.e., when electricity passes through it. Filament configurations are identified by letters and a suffix number (or number and letter) indicating the shape of the filament and the number of any supports.

Large Lamp Filaments

Miniature Filaments

Filaments for miniature and subminiature lamps may be a straight wire (S), a coil (C), or a coiled coil (CC). Coiling the filament wire effectively shortens the filament length so that smaller bulbs can be used. In addition, in gas-filled lamps, coiling the wire reduces thermal losses and increases efficiency.

Tungsten is almost universally used as lamp filament material because of its high melting point at incandescence. The number following the coil identification letter(s) denotes the arrangement of the filament on the supports.

Gas filled lamps use an inert gas to protect the filament during operation. In most automotive lamps, the gas most used is a mixture of 88% argon and 12% nitrogen. The pressure of the fill gas at room temperature is about 3/4 of an atmosphere.

The use of a fill gas reduces the net rate of tungsten evaporation by several orders of magnitude, so that little blackening of the bulb occurs during the life of the lamp. Since the net evaporation rate in gas is less than in a vacuum, the filament can be operated at a higher temperature for the same life. For this reason , gas filled lamps are more efficient than vacuum lamps.

The blackening that does occur is usually confined to the top of the bulb because of convection currents produced during operation. To avoid "water cycle" and premature blackening, "getters" are usually used to chemically or physically bind contaminants and assure a "clean" fill gas. Purity of the gas fill initially and during operation is critical in gas filled lamps.

A halogen lamp is an incandescent lamp with a filament that is surrounded by halogen gases, such as iodine or bromine. Halogen gases allow the filaments to be operated at higher temperatures and higher efficacies. The halogen participates in a tungsten transport cycle, returning tungsten to the filament and prolonging lamp life.

Halogen lamps, in addition to being gas filled, have a gaseous halogen compound added to the gas fill. The halogen compound constitutes a small portion of the fill gas and must be accurately controlled. The quantity used is on the order of 100 parts per million of fill gas and is usually a bromine compound. Its purpose is to prevent any blackening of the bulb by returning evaporated tungsten back to the filament through a "halogen cycle". Too little halogen permits blackening of the bulb to occur. Too much halogen destroys the tungsten filament.

Since with proper operation of the "halogen cycle" no blackening occurs, the bulb can be smaller than what is normally used in regular gas filled lamps. With smaller envelopes, higher molecular weight inert gasses and higher fill pressures are practical. Krypton is generally used in automotive halogen lamps and the fill pressure at room temperature is approximately 5 atmospheres.

The higher molecular weight gas and higher fill pressure permits operation of the filament at even higher temperatures than regular gas filled lamps, so that for the same life, halogen lamps have the highest efficiency of all miniature lamps.

The family of HID lamps includes the following lamp types: mercury vapor, metal halide, high-pressure sodium and less common, xenon short-arc lights. The light-producing element of these light types is a well-stabilized arc discharge contained within a refractory envelope, or arc tube.

A light source that generates light utilizing a thin filament wire (usually of tungsten) heated to white heat by an electric current passing through it.

LEDs are based on the semiconductor diode. When the diode is switched on, electrons are able to recombine with holes and energy is released in the form of light. This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. The LED is usually small in area (less than 1 mm2) with integrated optical components to shape its radiation pattern and assist in reflection.

LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching. However, they are relatively expensive and require more precise current and heat management than traditional light sources.

Applications of LEDs are diverse. They are used as low-energy replacements for traditional light sources in well-established applications such as indicators and automotive lighting. The compact size of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in communications technology.

Sunray LED Products

The distance between the center of the filament, or arc tube, and a reference plane - usually the bottom of the lamp base.

LCL is measured from the geometric center of the lighted filament to that part of the base listed below:

The term miniature lamp applies to units ranging in size from the so-called "grain of wheat" lamps to automotive headlights. It is not as much indicative of physical size as of low operating voltage - rarely more than 28 volts and often as little as 1.5 or 2.5 volts.

Sunray Lighting Miniature Catalog

Sunray Lighting Product Listing (2004)

For most lamp types, rated lamp life is the length of time of a statistically large sample between first use and the point when 50% of the lamps have died. It is possible to define "useful life" of a lamp based on practical considerations involving lumen depreciation and color shift.

Rated life is not guaranteed life and does not necessarily represent service life expectancy. Rated life, along with rated amperes at design volts, is a factor establishing the laboratory efficiency of a lamp. It is useful only as an index of comparative longevity of various lamps.

The life of an incandescent filament is voltage sensitive. A 10% increase in applied voltage will reduce the filament life to only 30% of its design value, while a 10% decrease in applied voltage will multiply the design life by a factor of approximately three. It is often feasible to "derate" an incandescent lamp for the sake of increased life.

The source of light in all miniature lamps is an incandescent tungsten filament which must be protected from exposure to the atmosphere. In vacuum type lamps, the filament is protected by processing the lamp so that a vacuum exists inside the glass envelope. The level of vacuum prior to operation of the lamp is on the order of 10-2 mm Hg or better, and during operation lamps will generally improve to about 10-4 mm Hg because of gettering of residual gasses by tungsten evaporation.

Tungsten evaporation rates in vacuum lamps are generally much higher than in gas filled or halogen lamp types. As a consequence, normal bulb blackening causes an almost constant decrease in light output during the life of the lamp.