Do red LEDs use less power?
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jtr1962
Flashaholic
Reds are certainly more efficient than whites with a red filter, probably by a factor a three or four. However, in terms of overall efficiency emitting visible light whites are actually better, although not by much. I recently measured some 9000 mcd reds at roughly 40 lm/W. The same company now has 11,000 mcd with a similar beam angle which should manage in the high 40s. The better 5mm whites are in the 60 to 75 lm/W range according to my tests. However, that doesn't tell the whole story. In terms of converting energy to light the best whites are about 20% efficient while the best reds are probably around 35% or so. The lumens per watt are less simply because our eyes are less sensitive to narrowband red light than to white.
Yes, at 20 mA drive current reds use less because their Vf is in the 1.9 to 2.1 volt area instead of the 3.2 to 3.6V typical of whites.
Yes, at 20 mA drive current reds use less because their Vf is in the 1.9 to 2.1 volt area instead of the 3.2 to 3.6V typical of whites.
scaredofthedark
Enlightened
jtr1962 said:
narrow band red light??? what does that mean?
i thought red has the longest wavelengths in the visible spectrum
cratz2
Flashlight Enthusiast
I think by narrow band, he is referring to the fact that it isn't a wide range such as white but only a limited range of color.
I tell you, I have a Garrity Stainless pen light with about a 7,000 MCD (might be a 9,000) LED into that I put two, we'll say, 80% fresh NiMH cells into and it's still as bright today as when I put it together a year ago... Granted, I don't use it every day, but it seems to last and last and last.
I tell you, I have a Garrity Stainless pen light with about a 7,000 MCD (might be a 9,000) LED into that I put two, we'll say, 80% fresh NiMH cells into and it's still as bright today as when I put it together a year ago... Granted, I don't use it every day, but it seems to last and last and last.
PhotonWrangler
Flashaholic
Narrowband = monochromatic. For instance, one of the reasons why LED traffic lights stand out among the visual clutter of a busy intersection is that their color is fairly "pure" or monochromatic, something that we usually don't see in nature. An incandescent red traffic light doesn't stand out as much, partly because the "red" actually contains many wavelengths of reddish-orangeish colors.
When you look at a spec sheet for an LED (other than white), you'll see a dominant wavelength specified. While the LED may put out a few other wavelengths very close to the dominant one, they're greatly attenuated. LEDs are extremely efficient compared to incandescents in producing a particular color because of this.
When you look at a spec sheet for an LED (other than white), you'll see a dominant wavelength specified. While the LED may put out a few other wavelengths very close to the dominant one, they're greatly attenuated. LEDs are extremely efficient compared to incandescents in producing a particular color because of this.
