5

Nowadays we see LEDs with 300 lumen per watt luminous efficacy. Maybe in the laboratory. Right now commercially available white LEDs are about 200 lm/w. 400 lm/w is the practical upper theoretical limit. US DOE estimated over 250 lm/w by 2025. Commercial Blue LEDs have up to about 80% efficacy (Cree XP-3G and OSRAM Oslon SSL). White LEDs use blue LEDs ...


5

It depends on what spectrum of light you want. Our eyes are most sensitive to green light at 555 nm, so a perfectly efficient light source that only emitted that color would reach 683 lm/W. If you want to include other colors (say, to get white light), you'll need more power for the same apparent brightness. Wikipedia has a great summary at https://en....


5

The answer to this question is heavily context-dependent. Short answer: it depends on which kind of bulb you are talking about. As someone already pointed out some bulbs are filled with some gas, therefore ambient temperature variation can be transmitted to the internal environment of the bulb, thus the vacuum problem is essentially moot (probably the ...


4

I should have researched more before asking. On this page it is explained: http://www.osram.com/osram_com/news-and-knowledge/halogen-lamps/professional-knowledge/high-voltage-and-low-voltage-lamps/index.jsp The key factors are the physical properties determined by the laws of electricity. The coiled wire of a low voltage lamp is about five times as thick ...


4

Would I get a better lumen output and improved thermal characteristics for the same wattage if I get a higher rated LED? The cost of thermal management is high for CoBs. More and lower wattage LEDs are usually most efficient. Efficacy usually drops when you exceed the "test current". What I do is implement the best thermal management I can do then ...


3

1). You need to get familiar with LED specs. 2)Then finally after you learn a bit, you may prefer the benefits of man-years of R&D and choose the best tail lights that fit your surface design or modify to fit. Your choices are amateurish. Pick from Buick, Lexus, Mercedes, BMW etc. Audi was the first to use LEDs over 10 years ago. Go to a pick-a-part ...


3

You could wire a resistor in series with the base. The lamps are claimed to be 2W so they should draw around 170mA from the 12V bus. Try about 10-50 ohms 1W to get the brightness you want. Of course you will no longer be able to safely install an incandescent bulb, in fact doing that could cause the resistor to get dangerously hot. You could add a small ...


3

in datasheets why measure of light output of power LEDs are given in lumens (luminous flux) but standard 5mm LEDs are given in mcd (luminous intensity)? Luminous flux measures the total visible light emitted by the LED. It's a useful spec if you're going to use the LED to illuminate a room. Luminous intensity measure the intensity of visible light emitted ...


3

I finally got my hands on some known diodes (as opposed to grab bag stuff) and adjusted them to equal perceived brightness (3 human observers) at a comfortable intensity for viewing from 15 feet (4.5m) away under good office lighting with the desk task light on. Led part (Vcc=5.15v) nm mCd Vf@mA Ohms mA Vdrop E-mCd WP3A10ID HE Red (...


2

Lumens are tailored around the characteristics of the human eye. If you take a look at the luminosity function, which is used as a wavelength dependent weighting for the lumens, you can see that the area around 550 nm or 500 nm depending on photopic (when a lot light is present) or scotopic (under low light conditions) is the most valued one, so it ...


2

To find the luminescence (in lumens) of a 21W bulb, you can multiply the power in Watts by the luminous efficacy (lm/W). The efficacy for a typical incandescent bulb will be about 15 lm/W, so you're looking at about 315 lumens. Then it seems you are trying to find the amount of LEDs that will provide the same luminescence. If the LED's datasheet has the ...


2

Halogen bulbs depend on the envelope running very hot (600-900C according to this forensics report) to recover tungsten, otherwise it can end up deposited on the inside of the quartz or high-temperature glass and both light output and filament life will suffer. You can see this effect with halogen bulbs that have been operated with a dimmer for long periods ...


2

You simply add the output of each LED to get the total output. The distance between the LEDs will have negligible effect. One confusing aspect of the angles used in optical measurements is the candela "view angle" (luminous intensity) and the angle at which the light travels (illuminance). For example let's use the LED you selected. The Kingsbright ...


1

My goal is have a low-cost yet high quality adjustable light for photography and the occasional videography, Short-life high-power incandescent bulb. Or use a standard bulb and overvoltage it. The light is for sure better than that from any LED, CFL or similar. The only thing even cheaper and also much much better is a reflector panel for sunlight. And ...


1

1) no, 2) yes, 3) almost certainly yes, 4) most of the time yes but see below. The 60W limit on the lamp is to prevent it overheating and catching fire. That means that you could, in principle, put a 60W LED in the lamp and it would be OK, or at least the lamp shroud would not catch fire. An LED must run at a much lower temperature (about 25-50C) than an ...


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