LED domestic lighting

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I've seen it stated on a number of occasions. I have not personally tested it but it sounded plausable. BTW, the frequency range over which it works is not wide. It needs to be above the optical fusion frequency (varies from one person to another, but never higher than 70Hz), and below the frequency response of the receptors and optic nerve (which I believe is always over 100Hz, well over in some people). One person I spoke to about it a while back didn't think the frequency response of the optic nerve was the upper limit for the effect to work (thought it was higher). These frequences vary a little across the field of vision too, and with other factors.
--
Andrew Gabriel

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Early LEDs did have a light output that increased more than the current increase, so it certainly made sense to operate LEDs in a high current, low duty cycle pulsed mode. Modern LEDs are more linear, so the only reason for pulsing would be to make the brightness adjustable (or constant, as the battery goes down), or maybe to resolve differences between the dc supply and the LED's fwd voltage drop (but that would need an associated inductor/transformer).
I have also seen the opinion on another newsgroup (c/w research references) that pulsed LEDs can appear brighter in conditions of low ambient light levels (ie, if our eyes are dark-adapted).
--
Tony Williams.

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wrote:

I'm really glad I asked this question.
I think.
Mary

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"Dave Plowman" wrote | Mike Barnes wrote: | > Well, yes, but they'd only need to be replaced every few decades. The | > lamps, that is. | I'm not so sure. Once you start driving LEDs hard as a light source rather | than just an indicator, their life span reduces dramatically.
I noticed last time I was passing through Waverley that the solari-style LEDboards had some characters missing.
The main concourse ones were advertising trains calling at Newcas and Leices and the ticket hall ones were welcoming passengers to the First ass Lounge.
Owain
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There is also the sulphur-microwave system although this is aimed at industrial applications. While it achieves about 70% efficiency, less than LED, it does give continuous spectrum. I understand that the idea is that you distribute it with fibre optics, as several kilowatts of illumination are a little excessive even for reading fine print.
http://ateam.lbl.gov/Design-Guide/DGHtm/futureremotelightingsources.htm
John Schmitt
-- If you have nothing to say, or rather, something extremely stupid and obvious, say it, but in a 'plonking' tone of voice - i.e. roundly, but hollowly and dogmatically. - Stephen Potter
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http://www.visionelements.co.uk/illumination/led_home.html
--
BigWallop

http://basecuritysystems.no-ip.com
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The GU10 is a 230V 50W mains halogen and the LED version is a direct replacement, although a slightly reduced light output. I had been paying around 4.50 for 4000 hour halogen GU10's but managed to get a load of LED replacements at trade cost, and figure they are more cost effective as they only consume 4W and last 12 time longer.
http://www.bltdirect.co.uk/item562.htm
Have seen them advertised for 12.00 but lost the URL
Dave
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They exist, but the best LEDs are currently only around the same efficiency as filament lamps, which means they get just as hot and die quickly or are lower power and lower light output (if you are thinking along the lines of retrofit lamps). They don't get to the efficiency of fluorescent lamps yet.
The area where I expect they will initially make inroads is where their very narrow beam angle can be used to advantage. In such applications they can exceed filament lamps in overall system efficiency because they don't spill light where it's not wanted.

The white ones are UV with fluorescent phosphors, so they can be made same colours as fluorescent lamps in theory, but I suspect there's no demand for 2700K ones. Also, the efficiency of the phosphor will reduce slightly for lower colour temperature and at the moment everyone is after highest brightness, so that would not be a lot of interest to manufacturers.
--
Andrew Gabriel

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But efficiency and acceptability aren't the same thing. I dislike the quality of light produced by fluorescent 'bulbs', no matter how they are modified to produce 'daylight', 'warm' or other qualities.

Filters?
Hmm. I didn't think my simple question would be answered so quickly, fully or technically but I'm grateful to everyone who has joined the conversation. If it continues I shall too :-)
Mary

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lamp (the CatEye LED300) is just as bright as their old standard krypton bulbed lamp (the HL-500 was it?) and runs several times as long.
I don't know whether this is down to them being efficient at low voltages or what but has revolutionised cycle lighting, front lamps can now realistically be run on AA cells.
--
Chris Green ( snipped-for-privacy@x-1.net)

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     snipped-for-privacy@isbd.co.uk writes:

Sorry, but this is a very common misconception. They can produce excellent high brightness narrow beams of light, which a filament lamp can't. This can be an advantage in some applications like spotlamps so the beam might look brighter than a filament lamp. However, if you take something like a 10 beam angle, which is 78 square degrees, and divide by the 41253 square degrees in the sphere which a filament lamp lights, this shows that the LED is only lighting up 0.2% of the area which the filament lamp did. That's why they appear so efficient, but in fact they aren't.
Nobody can currently get 30 lumens/watt from a white LED, which is what you get from highest efficiency halogen lamp. Nichia are predicting 60 lumens/watt for a product they expect to ship in 2005, which is still less than a fluorescent lamp. The efficiency improvement manufacturers have managed over the last couple of years is very disappointing compared with what went before, so it may be that some type of limit has now been reached without a significant change in technology.
--
Andrew Gabriel

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snipped-for-privacy@isbd.co.uk writes

You can certainly buy cycle lamps with what are described as halogen bulbs - btw, has the law been updated yet to allow cyclists to use non-filament bulbs?
--
dave @ stejonda

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LED front ones do as well so presumably they're legal as they conform to the required British Standard.
--
Chris Green ( snipped-for-privacy@x-1.net)

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writes

--
geoff

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The only restrictions relate to steady lights and red to rear. http://www.hmso.gov.uk/si/si1989/Uksi_19891796_en_1.htm http://www.hmso.gov.uk/si/si1994/Uksi_19942280_en_1.htm
I believe some flashing lights are now allowed, but can't find that.
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On 15 Jul 2003 19:45:36 GMT, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

http://www.lumileds.com/ has a PDF about a forthcoming 3200k" Warm White, Incandescent-Equivalent LED" shipping in August (it talks about LEDs "rapidly gaining traction" in general lighting, ...we give them a byootiful language and what do they do to it.............) 3200K is around quartz halogen colour temp (tho being flouro based I'm guessing the "quality" of the light whould be like that of a Warm White fluro) IIRK one of the probs with white LEDs is the colour isn't stable with time.
Lumileds has some impressive 5w suckers with heatsinks on the back but it's Nichia's 50mW blue or violet lasers that I covet!
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snipped-for-privacy@ntlworld.com wrote:

Could have been worse - they could have been rapidly gaining leverage!

a CRI of 85 would be considered poor for a fluoro, but is good compared with previous LEDs

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Interesting article in todays New Scientist suggest that further research into tungsten filaments is showing that 50% efficiency may be possible - as opposed to 25% for fluorescents.
I have posted the article at
http://nanohelix.tripod.com/ns.jpg
Dave

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I went to it eagerly.
I can't read it :-(
What's more, I can't convert it into a readable form :-((
Mary

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Mary Fisher wrote:

What problem did you experience Mary? I can see it OK, and it's well worth reading.
--
Grunff


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