Musings on the progress of LED lighting.

Ian Stirling · 2008-06-22T17:16:39+00:00

Back in 2003/4/5 I made some posts to this group on the topic of LED lighting,and I thought it was interesting to come back and reflect on the state ofthe art.Over the past few years, prices of high power LEDs have crashed, and theefficiency of the lower end of the scale has risen. - for example - 12W LEDfor 12 quid - with 620 lumens output or so - about 50lm/w, comparable withthe lower end CFLs. - at the higher end - if you use 12 of these, you get 12W, but with perhaps twice the brightness.One of - a universalpower supply - 10 of the above, and you get a 1000lm light, that uses maybe12W - practically as efficient as a linear fluorescant, and much betterthan a compact one, as bright as a 100W conventional light, for around 40 quid, and that's not even in volume.If you're making a few thousand, you could probably sell them for that.Admittedly, at the moment, the light colour from the above is pretty horrible, and has almost no yellow.At the moment nice warm white ones are about half the brightness.So - some way to go, but it's catching up fast to CFL.The dealextreme site (only a customer) also has other fun stuff.I plan to take one of the above 12W LEDs, one of and do a starscape of thebrightest 300 or so stars.Also experimenting with use in steps.Pour little bit of concrete, put some fibers on top, pour bit more, repeatuntil mold is full, then clean off with angle-grinder to expose the ends.I'm also trying to source high refractive index spheres - as used in reflective paint - to make a virtual sky light.

Jun 22, 2008 30 Replies

Rate this thread:

Andy Champ 18 years ago

True. But the "white paper" I'm typing on right know is a pseudo-white made from RGB, and I'll be amazed if the spectrum is anything like continuous.

Source please. (others have already backed me up)

Andy

Vote

Adam Aglionby 18 years ago

Theres a fluro tube colour called Rosetta that has a boosted red end , it dosen`t appear that way but red meat looks all the fresher under it.

Adam

Vote

Adam Aglionby 18 years ago

Spectrum not being same as spectral power distribution, Lumileds data sheet you flag up shows a big peak in deep red , tungsten shows a realtively straight line, low at blue and rising to red, but no peaks and troughs.

Adam

Vote

Adam Aglionby 18 years ago

LED is getting in as LCD backlight on a lot of things , usually with RGB sources rather than phosphor based lamps.

Most of them do which was another part of Shuji Nakamura`s discovery when working for Nichia, whose main business for previous 40 years had been phosphors for CRT screens.

Adam

Vote

Adam Aglionby 18 years ago

messagenews: snipped-for-privacy@davenoise.co.uk...

Colour Appearence as in how the light appears aginst Colour Rendering Index which tells you how accurately colours will be shown.

Adam

Vote

Dave Plowman (News) 18 years ago

Growlux - used for forcing plants - tends to enhance many colours.

Vote

John Rumm 18 years ago

It isn't - there are big gaps in the gamut produced by CRT or LCD RGB screens.

The rendition from other colour spaces is different again - which is why it is difficult to get accurate colour representation of material printed in CMYK from RGB sourced images.

Vote

Andrew Gabriel 18 years ago

That's enhanced red for chlorophyll operation, at the expense of blue and green which chlorophyll can't use. (Some plants need other specific wavelengths to encourage flower production though.)

2700K warm white is almost as effective for plant growth, and makes the colours look better to the human eye.

Vote

Mary Fisher 18 years ago

Trouble is that the best meat isn't that horrid bright red ...

Mary

Vote

Ian Stirling 18 years ago

Tungsten has a huge amount of energy in the IR, and slopes off towards the visible -

formatting link

the first graph.

For example - comparing the point at which the LED starts dropping off at the red - 670nm, the eye has a responsivity of well under 5% of its peak efficiency. Over the range 670-400nm, the match is moderateley good - neglecting the small peak at 470nm or so. (talking of the warm white LED spectrum on page 8, fig 2A of the luxeon datasheet)

Vote

Adam Aglionby 18 years ago

formatting link

the first graph.

Admittedly talking good warm white LEDs, they`re definately not all equal, compare the Nichia NCCL023 warm white LED; circa. December

2004. with a no brand, graph directly below Nichia, about 1/4 down page:

formatting link

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required