Effect of voltage on performance of Halogen lamp

Tungsten halogen lamps behave in a similar manner to other incandescent lamps when run on a different voltage. However the light output is reported as proportional to voltage to the power of 3, and the efficacy proportional to the power of 1.3. The normal relationship regarding life is that it is proportional to voltage to the power of −14. For example, a bulb operated at 5% higher than its design voltage would produce about 15% more light, and the efficacy would be about 6.5% higher, but would be expected to have only half the rated life. Continue reading “Effect of voltage on performance of Halogen lamp”

Voltage, light output, and lifetime

ncandescent lamps are very sensitive to changes in the supply voltage. These characteristics are of great practical and economic importance.

For a supply voltage V near the rated voltage of the lamp:

Lamp bases

Very small lamps may have the filament support wires extended through the base of the lamp, and can be directly soldered to a printed circuit board for connections. Some reflector-type lamps include screw terminals for connection of wires. Most lamps have metal bases that fit in a socket to support the lamp and conduct current to the filament wires. Continue reading “Lamp bases”

Bulb shapes, sizes, and terms

Incandescent light bulbs come in a range of shapes and sizes. The names of the shapes may be slightly different in some regions. Many of these shapes have a designation consisting of one or more letters followed by one or more numbers, e.g. A55 or PAR38. The letters represent the shape of the bulb. The numbers represent the maximum diameter, either in eighths of an inch, or in millimetres, depending on the shape and the region. Continue reading “Bulb shapes, sizes, and terms”

Power of Light Bulb

Incandescent light bulbs are usually marketed according to the electrical power consumed. This is measured in watts and depends mainly on the resistance of the filament, which in turn depends mainly on the filament’s length, thickness, and material. For two bulbs of the same voltage, type, color, and clarity, the higher-powered bulb gives more light. Continue reading “Power of Light Bulb”

Light Bulb Electrical characteristics

Incandescent lamps are nearly pure resistive loads with a power factor of 1. This means the actual power consumed (in watts) and the apparent power (in volt-amperes) are equal. The actual resistance of the filament is temperature-dependent. The cold resistance of tungsten-filament lamps is about 1/15 the hot-filament resistance when the lamp is operating. Continue reading “Light Bulb Electrical characteristics”

Halogen lamps

The halogen lamp reduces uneven evaporation of the filament and darkening of the envelope by filling the lamp with a halogen gas at low pressure, rather than an inert gas. The halogen cycle increases the lifetime of the bulb and prevents its darkening by redepositing tungsten from the inside of the bulb back onto the filament. Continue reading “Halogen lamps”

Bulb blackening

In a conventional lamp, the evaporated tungsten eventually condenses on the inner surface of the glass envelope, darkening it. For bulbs that contain a vacuum, the darkening is uniform across the entire surface of the envelope. When a filling of inert gas is used, the evaporated tungsten is carried in the thermal convection currents of the gas, depositing preferentially on the uppermost part of the envelope and blackening just that portion of the envelope. Continue reading “Bulb blackening”

Reducing filament evaporation

One of the problems of the standard electric light bulb is evaporation of the filament. Small variations in resistivity along the filament cause “hot spots” to form at points of higher resistivity ; a variation of diameter of only 1% will cause a 25% reduction in service life. The hot spots evaporate faster than the rest of the filament, increasing resistance at that point—a positive feedback which ends in the familiar tiny gap in an otherwise healthy-looking filament. Irving Langmuir found that an inert gas, instead of vacuum, would retard evaporation. Continue reading “Reducing filament evaporation”

Light Bulb Filament

The first successful light bulb filaments were made of carbon (from carbonized paper or bamboo). Early carbon filaments had a negative temperature coefficient of resistance – as they got hotter, their electrical resistance decreased. This made the lamp sensitive to fluctuations in the power supply, since a small increase of voltage would cause the filament to heat up, reducing its resistance and causing it to draw even more power and heat even further. Continue reading “Light Bulb Filament”

Light Bulb Construction

Incandescent light bulbs consist of a glass enclosure (the envelope, or bulb) with a filament of tungsten wire inside the bulb, through which an electric current is passed. Contact wires and a base with two (or more) conductors provide electrical connections to the filament. Incandescent light bulbs usually contain a stem or glass mount anchored to the bulb’s base which allows the electrical contacts to run through the envelope without gas/air leaks. Continue reading “Light Bulb Construction”

Efforts to improve efficiency

Due to the measures noted above, there have been recent efforts to improve the efficiency of incandescents. For example the consumer lighting division of General Electric announced that they are working on a “high efficiency incandescent” (HEI) lamp, which they claim could ultimately be as much as four times more efficient than current incandescents, although their initial production goal is to be approximately two times more efficient. Continue reading “Efforts to improve efficiency”

Cost of lighting

The desired product of any electric lighting system is light (lumens), not power (watts). To compare incandescent lamp operating cost with other light sources, the calculation must also consider the lumens produced by each lamp. For commercial and industrial lighting systems the comparison must also include the required illumination level, the capital cost of the lamp, Continue reading “Cost of lighting”

Light Bulb Commercialization

Joseph Wilson Swan (1828–1914) was a British physicist and chemist. In 1850, he began working with carbonized paper filaments in an evacuated glass bulb. By 1860 he was able to demonstrate a working device but the lack of a good vacuum and an adequate supply of electricity resulted in a short lifetime for the bulb and an inefficient source of light. By the mid-1870s better pumps became available, and Swan returned to his experiments. Continue reading “Light Bulb Commercialization”

Early pre-commercial research of light bulb

In 1802, Humphry Davy had what was then the most powerful electrical battery in the world at the Royal Institution of Great Britain. In that year, he created the first incandescent light by passing the current through a thin strip of platinum, chosen because the metal had an extremely high melting point. It was not bright enough nor did it last long enough to be practical, but it was the precedent behind the efforts of scores of experimenters over the next 75 years. In 1809, Davy also created the first arc lamp by making a small but blinding electrical connection between two carbon charcoal rods connected to a 2000-cell battery; it was demonstrated to the Royal Institution in 1810. Continue reading “Early pre-commercial research of light bulb”

Producers of plasma lamp

Companies producing or developing plasma lamps include Ceravision, Luxim and Topanga Technologies.

Luxim’s LIFI, or light fidelity lamp, claims 120 lumens per RF watt (ie before taking into account electrical losses). The lamp has been used in Robe lighting’s ROBIN 300 Plasma Spot moving headlight. It was also used in a line of, now discontinued, Panasonic rear projection TV. Continue reading “Producers of plasma lamp”

High-efficiency plasma (HEP)

High-efficiency plasma lighting is the class of plasma lamps that have system efficiencies of 90 lumens per watt or more. Lamps in this class are potentially the most energy efficient light source for outdoor, commercial and industrial lighting. This is due not only to their high system efficiency but also to the small light source they present enabling very high luminaire efficiency. Continue reading “High-efficiency plasma (HEP)”

Legal implications for traffic lights

In virtually all jurisdictions in which they are used, it is an offence for motorists (and other road users) to disregard the instructions of traffic lights (or other traffic control devices). Exceptionally, it is not an offence for pedestrians to cross against a red light in the United Kingdom, where pedestrian lights officially give advice, rather than an instruction, although UK pedestrians do commit an offence if they cross a road against the signals of a police officer controlling traffic. Continue reading “Legal implications for traffic lights”

Traffic signal warrants

Traffic signals have strengths and weaknesses that must be considered when deciding whether to install them. Signaled intersections can reduce delay for side road traffic and reduce the occurrence of collisions by turning traffic and cross traffic. But they may also cause delay for traffic on the main road, and often increase rear-end collisions by up to 50%. Since right-angled and turn-against-traffic collisions are more likely to result in injuries, this is often an acceptable tradeoff. Continue reading “Traffic signal warrants”

Small vehicle safety of Traffic lights

In some instances the stoplight traffic detector will not change the light for small vehicles such as motorcycles and scooters. This is the result of the inability of the sensors to detect the presence of the small vehicle. A vehicle with sufficient mass consisting of a metal such as steel interacts with the sensors magnetic field causing the light to change at the appropriate time. Continue reading “Small vehicle safety of Traffic lights”

Traffic lights Implementation

According to transportation engineers, traffic lights can have both positive and negative effects on traffic safety and traffic flow. The separation of conflicting streams of traffic in time can reduce the chances of right-angle collisions. But also the frequency of rear-end crashes can be increased by the installation of traffic lights, and they can adversely affect the safety of bicycle and pedestrian traffic. Continue reading “Traffic lights Implementation”

Mounting of Traffic lights

There are significant differences from place to place in how traffic lights are mounted or positioned so that they are visible to drivers. Depending upon the location, traffic lights may be mounted on poles situated on street corners, hung from horizontal poles or wires strung over the roadway, or installed within large horizontal gantries that extend out from the corner and over the right-of-way. In the last case, such poles or gantries often have a lit sign with the name of the cross-street. Continue reading “Mounting of Traffic lights”

Traffic Light design

In the United States, traffic lights are currently designed with lights approximately 12 inches (300 mm) in diameter. Previously the standard had been 8 inches (200 mm), however those are slowly being phased out in favor of the larger and more visible 12 inch lights. Variations used have also included a hybrid design, which had one or more 12 inch lights along with one or more lights of 8 inches (200 mm) on the same light. Continue reading “Traffic Light design”

Conventional lighting systems of Traffic lights

Conventional traffic signal lighting, still common in some areas, utilizes a standard light bulb. Typically, a 67 watt, 69 watt, or 115 watt medium-base (household lamp in the U.S) light bulb provides the illumination. Light then bounces off a mirrored glass or polished aluminium reflector bowl, and out through a polycarbonate plastic or glass signal lens. Continue reading “Conventional lighting systems of Traffic lights”

Programmable Visibility Signals of Traffic Lights

Signals such as the 3M High Visibility Signal and McCain Programmable Visibility signal, utilize light diffusing optics and a powerful fresnel lens to create the signal indication. Lit via a powerful 150W PAR46 sealed-beam lamp, the light from the lamp in these “programmable visibility” signals passes through a set of two glass lenses at the back of the signal. The first lens, a frosted glass diffusing lens, diffuses the light into a uniform ball of light around five inches in diameter. The light then passes through a nearly identical lens known as an optical limiter (3M’s definition of the lens itself), also known as a “programming lens”, also five inches in diameter. Continue reading “Programmable Visibility Signals of Traffic Lights”

Optics and lighting of Traffic Lights

In the mid 1990s, cost-effective traffic light lamps using light-emitting diodes (LEDs) were developed; prior to this date traffic lights were designed using incandescent or halogen light bulbs. Unlike the incandescent-based lamps, which use a single large bulb, the LED-based lamps consist of an array of LED elements, arranged in various patterns. When viewed from a distance, the array appears as a continuous light source. Continue reading “Optics and lighting of Traffic Lights”