How Do Lights Age?
- May 08, 2018 -

    How old is the world's longest-living incandescent bulb?



    It is 115 years old this year.

    It still works at livermore fire station.

    In order to observe the 100-year light bulb, a real-time monitor has been placed around it, and the bulb is said to have "killed" two video monitors.

    The 100-year light bulb has been working for 115 years since 1901.

    In addition to the blackout, the light bulb went out only once in 1976 and 2013.

    1976, firefighters to bulb when we move, in order not to damage the light bulb, they use the screwdriver bulb turned down, but to cut off the rope, escorted by the police and fire engines, displacement to continue to work elsewhere.



    People care for this 100 - year - old bulb.

    It is understood that the livermore light bulb is a hand-blown incandescent lamp with a built-in carbon filament.

    The researchers compared the 100 years' worth of light bulbs to the average light bulb, and found that the difference between the livermore bulb and the ordinary bulb was mainly reflected in two aspects:


    The filament is eight times thicker than the ordinary filament.


    The filament used in a 100-year light bulb may be a semiconductor made of carbon filament.



    The higher the conductor temperature, the lower the conductivity.

    But the higher the conductor temperature of a 100-year bulb, the more conductive it will be.



    However, scientists have not yet figured out exactly why the livermore bulb is long.

    Although it is not clear exactly when the bulb will start working, firefighters will designate June 18 each year as its "birthday."

    "Livemore", translated into Chinese is "live longer", so the light bulb in California "live longer region live longer fire station" has been lit up more than 100, if the calculation in 115, the lamp really lit up more than 1 million hours.



    It has to be said that it is just a magical example. For various reasons, our usual use experience is usually: the lamp that has just been bought is very bright when used.

Use time is long, the brightness of the lamp slowly decreases, until finally extinguished.


    We all know that this is the life of lamps and lanterns to shorten slowly, wait until one day completely not bright, also die a dead end.

    Many people can not help wondering why there is such a process in the lamps and lanterns, what causes it?

    In fact, after all, this is the problem of light of lamps and lanterns, simply say, lamps and lanterns and human body, with the increase of service life, the function mechanism of lamps and lanterns is in ceaseless decline.

    Whether incandescent lamps, fluorescent lamps, or LED lights can't avoid the problem of light decay.



    The light of lamps and lanterns of lamps and lanterns, it is to point to lamps and lanterns after a period of time is illuminated, its light intensity will be lower than original light intensity, and low part is the light of lamps and lanterns of lamps and lanterns.

    Different types of lamps cause different reasons for light failure.



    Ordinary incandescent light fades.


    For ordinary incandescent lamps, the larger the bubble shell is, the smaller the light attenuation is, which means that the evaporation of tungsten is directly proportional to the output of the light.

    The gas-filled bulb will be smaller because some of the gas prevents the tungsten from evaporating.



    If an incandescent lamp USES the same filament, in a different bubble shell, it is true that the light of the same time point is smaller than the bubble shell.

    In addition, the same is inflatable bubble, big glass shell bulb internal space, air convection to the glass shell has a relatively large cooling area, relatively small glass shell lamp at a lower temperature, the temperature of the filament is relatively low, luminous efficiency is low, tungsten filament evaporation rate is low, so the light failure is small.



    Fluorescent light fade

    Incandescent light bulb will cause the light decline due to the size of bulb and the evaporation of tungsten filament, and the reason of the light failure of fluorescent lamp is relatively complicated, which is usually caused by the following reasons:



    In the process of fluorescent lighting, ultraviolet light will cause the phosphor to produce a new absorption band, which will reduce the brightness of fluorescent powder.



    Film formation of suction light, fluorescent light after a long discharge after work, on the surface of phosphor powder can form a layer of black film suction light, the existence of this layer suction light thin film will cause the decrease of light output.



    Working lamp black, fluorescent lamp, glass tube surface will have a large amount of mercury ion or mercury atoms exist, mercury ions ion exchange with other ions inside the glass tube, long down, glass tube will be black, resulting in fluorescent light failure, affect the luminous efficiency.


    Figure: typical light failure curve of T5 fluorescent lamp.

    The LED light failure


    Although the LED lamps and lanterns are improved than incandescent lamps and fluorescent lamps, they cannot completely overcome the problem of light decay.

    There are two main factors for the light failure of LED:



    LED product quality problem.


    The quality of LED chip is not good, and the brightness decays faster.


    There are defects in the production process, and the LED chip is not good enough to be exported from the PIN, which leads to the high temperature of the LED chip and the increase of chip attenuation.


    Condition problem


    The LED is driven by constant current, and some LED lights are driven by voltage, so the LED is attenuated too fast.


    The driving current is greater than the rated driving condition.



    In fact, there are many reasons for the light failure of LED products, but the most important one is the heat dissipation problem.

    The better the heat dissipation performance, the lower the working temperature of the LED, the smaller the light attenuation, the longer the LED life.

    Figure: typical light failure curve of LED lights.



    Light failure is a necessary process of lamps and lanterns of work, when choosing lamps and lanterns, we should try to choose the quality and good heat dissipation performance of lamps and lanterns, in use process should also try to reduce the workload of lamps and lanterns, can delay the speed droop, extend the life of the lamps and lanterns.



    Whether to cope with the light decline, because of the ground and different.



    First of all, look at the requirements of illumination. If an office area is used, the illumination of the working face may really need 300lx. If substandard, it will bring fatigue and other discomfort.



    But is there really a difference between 300lx and 200lx for a hotel?

    Actually makes no difference, when the intensity of illumination is not important, more important is whether the illuminance distribution conforms to the atmosphere and scene construction target, and glare control, the hotel is this, we pay more attention to in the application of the feeling of the people went in, 300 lx and 200 lx actually not big difference, because the visual perception of people is flexible.



    Site of illumination, such as a salon's highest over 1000 lx, most dark place 10 lx, we don't feel very comfortable, and light and shade contrast also have an atmosphere, the hotel requires the effect, so for the hotel, intensity of illumination is not that important, that is to say, a range of light failure is not so important.

    Image: interior of the Bali W hotel.

    High contrast the use of the technique, is from drama stage lighting references, let a space have hierarchy and story, so, can say in these areas, uneven illumination, it is a must.

    Figure: sports venues, uniform and standard illuminance requirements, become very strict, and light failure is a factor that must be fully considered and effectively dealt with.


    Offices, museums, stadium these places, however, requires that must meet strict illuminance standard, and LED light life is long, we need to consider in the two years later, still have to meet the standards, so we design in the first place, will leave allowance.