So the regulations would have been set up in that manner because for a halogen globe to produce colder than 4300K almost certainly meant that it was also emitting a lot of UV.Īll that changed when LEDs became a viable option for vehicle headlights too. So the filtration(ie, the product that we see as the glass section of the globe) has to be cheap enough to buy. With filtration, you get leakage(unless cost is unlimited!) and with halogen globes cost is a major factor. Kelvin rating can roughly be translated into the various light specra, where a colder K value equated to more blue light emitted from the globe. So the halogen globe has to have the UV component attenuated in some way. Efficiency values for light from a heat source are typically less than two percent.I'd need to check the latest, but up until recently at least anything above 4300K wasn't legal for on road use.That would have been because halogens natively produce a lot of UV, and you don't want UV light blaring directly into your eyes over a long period of time. The visible power can be approximated by the area under the Planck curve between 300 nm and 700 nm for a blackbody at the temperature of the filament as a ratio of the total power under the blackbody curve. This is not to be confused with efficiency which is always a dimensionless ratio of output divided by input which for lighting relates to the watts of visible power as a fraction of the power consumed in watts. "In lighting design, "efficacy" refers to the amount of light (luminous flux ) produced by a lamp (a light bulb or other light source ), usually measured in lumens, as a ratio of the amount of power consumed to produce it, usually measured in watts. The "Efficacy" column is really interesting. Posted 01:19 (#1712435 - in reply to #1712375) Subject: Re: Lighting technology: Halogen vs. Here's a video on the incandescent light bulb filament: Īnd here's a chart showing the efficiency of each type of light: I think it is amazing that halogen lights run so hot that the tungsten actually evaporates, but the halogen gas is able to recycle the tungsten atoms by putting them back on the filament. As current flows through the LED, electrons jump across the wide band-gap junction between the N-type and the P-type materials to recombine with holes. LEDs work exactly the same as a standard p-n junction diode, except the semiconductor material used has a higher band-gap energy level. Unlike fluorescent lamps, though, HID lamps operate at a high temperature and high pressure, the arc length is very short, and visible light is produced directly without the need for a phosphor. HID lamps produce light using a technique similar to that used in fluorescent lamps. In addition, because the filament is running hotter, more light per unit energy is achieved, making halogen lamps ideal for “spot” lighting applications. This recycling process results in a much longer lasting filament versus incandescent. The halogen gas inside the envelope combines with tungsten atoms as they evaporate and re-deposits them back on the filament. Similar to an incandescent lamp, the electrical current heats the tungsten filament above 2500☌, causing the filament to get “white hot” and release light. Halogen lamps use a tungsten filament encased inside a small quartz envelope. The excited mercury atoms give off ultraviolet (UV ) light, which is then converted into visible light as it passes through the phosphor coating on the inside of the tube. As electrons flow across the tube from one filament to the other, they collide with mercury atoms. Less than 10% of the total energy consumed by the bulb actually produces light, while the rest is wasted as heat.įluorescent lamps consist of a glass tube filled with argon gas and a small amount of mercury and filaments located at each end. As current flows through the filament, the filament heats up to 2200☌, causing the metal atoms in the filament to release light. Incandescent lamps contain a tungsten filament resistor that’s connected directly across the ac line.
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