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Old 11th November 2012, 04:08 AM   #81
Pano is online now Pano  United States
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Originally Posted by AndrewT View Post
rubbish !
No not rubbish, just very slightly off the mark. The human eye sees 3 colors that overlap a bit, so not really 'narrow" bands. It's a trick of the eye that makes color TV, color film and most color printing possible. If we saw more colors or a real continuous spectrum then color reproduction would be vastly more difficult.

So for your color mixing LEDs, you need only 3 colors - Red, Green, Blue. You may want to pick their wavelength centers to correspond to the human eye filters for best results (see SMPTE phosphors). If the 3 colors did not work, then your computer monitor, TV, LED video walls, video projectors, etc would not work. But they do.

A problem you may run into is that the colors don't mix well because of the space between the individual Red, Green, Blue LEDs. Diffusers or a tight pitch can help there.
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Old 11th November 2012, 04:19 AM   #82
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Originally Posted by DUG View Post
My only concern is that to save on electricity the industry is producing "bulbs" that give off much less light than I would like. (that I am used to)

Some of the early attempts used 60% of normal bulb power but only gave 50% of light output...actually less efficient.

LED's do last longer but can't run as hot as incandescent bulbs when generating the same light output...they are getting better though.

I use one for a front light...it is strong enough to light up the house number and uses a lot less power than the regular bulb.

I guess it just depends on what you are replacing.

IMHO
I wanted to replace the 15 watt tubular bulbs in my aquarium with an LED so I ordered a 20 watt array chip from ebay. That 20 watts is like staring at the sun. In fact I'm sure it would cause as much damage as a MIG welder It lights up my entire back yard better than any floodlight can. Needless to say it would blind my fish if used at full brightness. I never did use it for that though. The only drawback is the size of the heatsink required. I eventually used it at work to replace a very expensive mercury lamp in an optical comparator.
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Old 11th November 2012, 08:27 AM   #83
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Originally Posted by astouffer View Post
That 20 watts is like staring at the sun. In fact I'm sure it would cause as much damage as a MIG welder
Does it come with a warning for retinal damage? When I bought a Makita power drill it included the ML100 flashlight. Very very bright for short distances, not focused enough for long distances. It comes with a class 2 laser warning...
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Old 11th November 2012, 09:17 AM   #84
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* Lighting is based on the equivalent emission of a hot wire (incandescent bulb)
So what you are really saying is that I need to pump more power into my amp for a cool lighting effect?
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Old 11th November 2012, 09:50 AM   #85
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I eventually used it at work to replace a very expensive mercury lamp in an optical comparator.
Do tell (more)
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Old 11th November 2012, 12:37 PM   #86
AndrewT is offline AndrewT  Scotland
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Originally Posted by tvrgeek View Post
As expected with much more detail than I knew or remembered.
But very clearly, the paper shows, we "see" the whole range of "colour".
NOT
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three narrow bands of color
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Old 11th November 2012, 12:38 PM   #87
tvrgeek is offline tvrgeek  United States
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Originally Posted by Pano View Post
No not rubbish, just very slightly off the mark. The human eye sees 3 colors that overlap a bit, so not really 'narrow" bands. It's a trick of the eye that makes color TV, color film and most color printing possible. If we saw more colors or a real continuous spectrum then color reproduction would be vastly more difficult.

So for your color mixing LEDs, you need only 3 colors - Red, Green, Blue. You may want to pick their wavelength centers to correspond to the human eye filters for best results (see SMPTE phosphors). If the 3 colors did not work, then your computer monitor, TV, LED video walls, video projectors, etc would not work. But they do.

A problem you may run into is that the colors don't mix well because of the space between the individual Red, Green, Blue LEDs. Diffusers or a tight pitch can help there.
The reference shows more overlap than my old bio text's from school.

LED's are narrow band, so a set of three do not produce the full color spectrum. Technical LED Color Chart But by only producing something close to our three center bands, we get a reasonable approximation of white with less energy used. The above reference does not show LED's also produce IR. It only shows the useful visible bands.

Last edited by tvrgeek; 11th November 2012 at 12:42 PM.
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Old 11th November 2012, 12:39 PM   #88
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Originally Posted by 5th element View Post
LEDs arent always silent either, but that's only if you're using PWM dimming as the inductor can sing at the PWM frequency. At 100% duty cycle though there is no noise.
We have a Phillips Lumiled kitchen fixture -- the PWM does sing and the old dimmer has settings which cause the diodes to flash! We were also able to use a recessed LED fixture in the bedrooms -- fit in a pretty tight space where only a fluorescent could have gone before.

It's a very nice looking fixture and we were able to locate it above the kitchen dining table in a manner which nicely illuminates the table.

Saying this, however, the 3-way incandescent I have where I read in the evening also serves to keep me a little warmer -- and in the summer you don't have to turn it on until well after 8 pm.

CFL's remind me of the illumination in a Czech episode of "Sandbaggers".
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Old 11th November 2012, 12:45 PM   #89
AndrewT is offline AndrewT  Scotland
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Originally Posted by tvrgeek View Post
As I said, three bands. Described in the reference I pointed to. The reference shows more overlap than my old bio text's from school.
So much overlap that we see the continuous spectrum.

Imagine a test set up using a single band of colour emission.
Now sweep that light from one end of the visible to the other end.
We see the light emission as a continuous spectrum.
If we had non overlapping colour reception, the swept colour would appear to go out between the narrow band receptors. That's not the way our eyes work.
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Old 11th November 2012, 02:38 PM   #90
wwenze is offline wwenze  Singapore
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Originally Posted by jackinnj View Post
We have a Phillips Lumiled kitchen fixture -- the PWM does sing and the old dimmer has settings which cause the diodes to flash! We were also able to use a recessed LED fixture in the bedrooms -- fit in a pretty tight space where only a fluorescent could have gone before.

It's a very nice looking fixture and we were able to locate it above the kitchen dining table in a manner which nicely illuminates the table.

Saying this, however, the 3-way incandescent I have where I read in the evening also serves to keep me a little warmer -- and in the summer you don't have to turn it on until well after 8 pm.

CFL's remind me of the illumination in a Czech episode of "Sandbaggers".
I see the dimmer + flashing issue isn't unique to a single manufacturer's product. But then it's a Phillips... so the previous sentence may or may not be true...?

Does that lamp happen to be marketed as 'dimmable' via standard AC light dimmers?
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