LED headlights?

[email hidden] (B.C. Cletta) wrote in message news:<[email hidden]>...

Quoted message said:

"rosco" <reverse-the-following"ocsor_g"@hotmail.com> wrote in message
news:<[email hidden]>...

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My Luxeon Star based flashlight (Surefire E2e w/ KL1 head) has *much* better optics & beam
pattern.

what's the beam like? any potential for bike use? whenever i'm ever feeling fiscally
irresponsible, i think about getting a SureFire KL-3 LED head, and adapting it for use bike use. i
wish they published beam pattern info. BTW, they a pretty good info section.

new entry: <elektrolumens.comTri Star Bike Light.htmlOpen ↗

Steven M. Scharf said:

The problem with the LED lights is that they require multiple LEDs to achieve sufficient
brightness, and it is difficult to combine these into a usable beam for seeing the road (though
for being seen the LED lights are okay with a proper lens.

The problem you describe is related to the specific LEDs being used in those lights. 5mm LEDs vary
in the angle of beam they cast, with some as narrow as 10 degrees. And high-flux LEDs such as the
Lumileds Luxeon Star are available up to 5W, with a claimed 120 lumens from a single emitter.

lumileds.comstar index.htmlOpen ↗

I believe the reason that LED bike lights do not yet use such focused/focusable diodes is twofold:

1) Neither of the described options is the cheapest possible, and

2) The bike lights in question are intended to satisfy the usual legal requirement of making the
cyclist visible from a distance, rather than to provide useful illumination for the cyclist
to see by.

Chalo Colina

"Chalo" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

The problem you describe is related to the specific LEDs being used in those lights. 5mm LEDs vary
in the angle of beam they cast, with some as narrow as 10 degrees. And high-flux LEDs such as the
Lumileds Luxeon Star are available up to 5W, with a claimed 120 lumens from a single emitter.

lumileds.comstar index.htmlOpen ↗

I believe the reason that LED bike lights do not yet use such focused/focusable diodes is twofold:

1) Neither of the described options is the cheapest possible, and

2) The bike lights in question are intended to satisfy the usual legal requirement of making the
cyclist visible from a distance, rather than to provide useful illumination for the cyclist to
see by.

I think a third reason is that the 5W/120 lumen Lumileds Luxeon LED has a predicted MTTF of only 500
hours. This is much worse than a filament based lamp. Of course if you over-voltage a filament lamp
like Lumileds is over-currenting their LED, the filament lamp MTTF declines to about the same MTTF
as the LED, but it costs much more and does not produce as good of a beam.

It's rather interesting that an MR11 10W lamp, over-voltaged by 10%, has about the same lumens/watt
AND the same MTTF as a Luxeon 5W LED. An MR16 10W lamp has about twice the lumens/watt as Luxeon 5W
LED, and about the same MTTF, when over-voltaged by 10%. The price difference is enormous. And the
MR11 and MR16 are sufficiently convection cooled through a metal enclosure.

The fact that the 5W LEDs are expensive, don't provide useful illumination, and have a predicted
lifetime of 1/4 that of filament based lamps of the same wattage, probably has a lot to do with why
these LEDs are not being used!

Since reflectors and optics used in headlights are designed for a point source of light, using
multiple 1W LEDs doesn't help. Collimating a beam from multiple LEDs is not something that is done
well, cheaply or expensively. But as someone else pointed out, the multiple LED lights are good for
being seen, and good for riding on familiar, well-lit streets.

What some people (well one person) does not understand, is that an LED that is producing the
equivalent amount of light as a filament bulb, with the same efficiency, is generating a lot of heat
which must be managed. It has nothing to do with whether the source of the light is "white hot
metal" or a very hot emitter junction; both are burning up. A filament is easy to see burning up,
the emitter junction is not, but it is burning up none-the-less.

You know, not every use of a specific technology makes sense, no matter how bad people want it to
work. I think that people got excited about LEDs because of their wide-spread use in automotive
brake lights, traffic lights, etc, and just wanted so bad for them to work in making a usable beam.
Maybe someday the limitations will be overcome.

Steven M. Scharf said:

What some people (well one person) does not understand, is that an

LED that

Quoted message said:

is producing the equivalent amount of light as a filament bulb, with the same efficiency, is
generating a lot of heat which must be managed.

It has

Quoted message said:

nothing to do with whether the source of the light is "white hot

metal" or a

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very hot emitter junction; both are burning up. A filament is easy to see burning up, the emitter
junction is not, but it is burning up

none-the-less.

Obviously, Steven can't (or won't) understand my point, so I'll stop discussing that.

Quoted message said:

It's rather interesting that an MR11 10W lamp, over-voltaged by 10%, has about the same
lumens/watt AND the same MTTF as a Luxeon 5W LED. An MR16 10W lamp has about twice the lumens/watt
as Luxeon 5W LED, and about the same MTTF, when over-voltaged by 10%. The price difference is
enormous. And the MR11 and MR16 are sufficiently convection cooled through a metal enclosure.

The fact that the 5W LEDs are expensive, don't provide useful illumination, and have a predicted
lifetime of 1/4 that of filament based lamps of the same wattage, probably has a lot to do with
why these LEDs are not being used!

Since reflectors and optics used in headlights are designed for a point source of light, using
multiple 1W LEDs doesn't help. Collimating a beam from multiple LEDs is not something that is done
well, cheaply or expensively. But as someone else pointed out, the multiple LED lights are good
for being seen, and good for riding on familiar, well-lit streets.

You know, not every use of a specific technology makes sense, no matter how bad people want it to
work. I think that people got excited about LEDs because of their wide-spread use in automotive
brake lights, traffic lights, etc, and just wanted so bad for them to work in making a usable
beam. Maybe someday the limitations will be overcome.

Indeed. In fact, I'll bet on it.

Twenty years ago, LEDs were useful only as low-powered indicators, and had severe limitations when
viewed in full daylight. (Anybody remember trying to use an LED-based calculator outdoors?) An LED
flashlight would have been laughed at, and LED traffic lights weren't mentioned even in science
fiction. (Sheldon: insert Heinlein quote not mentioning LEDs here. ;-)

Since then, development has been exponential. More success breeds more interest and thus more
development work. In the same time period, advances in filament lights have been much less
dramatic. HID lights have made great strides, but the complexity of that system is a pretty severe
handicap, I think.

I'll be greatly surprised if in 2010 we don't have lots of LED bike lights that are better than
today's generator lights. IOW, very good indeed! ;-)

--
Frank Krygowski [To reply, omit what's between "at" and "cc"]

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What Lumileds is doing with their Luxeon 5W LED is basically over-driving them, raising the
junction temperature, trying to manage the thermal issues with heat sinks and perhaps fans, and
living with LED lifetimes that are less than that of a filament bulb. The Luxeon 1W is a good
product for some applications, but few people will accept the 500 hour limitation of their 5W LED.

Strange you would say that..

A lot of people accept the 100 hr limitation on the SON/Lumotec halogen bulbs?? Even you suggested
this is the best for a dynamo system.

For a typical cycle commuter, 1 hr for 5 days a week = 5 hrs/5 days. It means, a typical cycle
commuter will have to commute 500 days to kill the bulb. There are 365 days in a year, 1/4 of that
commuting during the long winter nights. So, it's really only about 90 to 100 days of the year that
you'll be needing lights. If it's 100 hrs per year use, that's 5 years. I think you'll find that a
LOT of people find this 500 hr limitation very acceptable indeed. Besides, 5 years down the road,
another better LED system will come out and replace the one we now have.

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I didn't propose "low power" LEDs. I was speculating that multiple LEDs

with improved integral lenses (and, perhaps, reflectors) might be used for lighting the road in
the future.

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I still think that's a strong possibility. I guess we'll see.

"The future" is a pretty long time. Certainly they won't be used in headlights on motor vehicles
in our lifetime due to the cost and intensity. As to bicycle lights, it's a possibility, but the
lumens/watt will have to be magnitudes better.

I am not sure that would be the case. British Petroleum (BP) just signed a contract with a local LED
company (TIR Systems) to supply and replace existing lighting fixtures on all their gas stations! If
BP felt that the LEDs are bright enough to light up their gas stations, LEDs must be doing a good
enough job. BP expects to save on their hydro bill. In fact, the newspaper goes on to quote this
company saying that it will be possible in OUR lifetime to create LEDs bright and good enough to
replace filament bulbs.

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I'm interested in more than one brand of LED.

I'm not aware of any other companies building LEDs as bright as the Lumileds ' Luxeon product. As
far as other brands of LEDs you can check out web sites of Vishay, Agilent, Fairchild etc. You'll
find that it terms of lumens/watt LEDs are comparable to incandescent lamps, not as efficient as
fluorescent or HID. The $/Lumen of LEDs is unfavorable, but improving and will eventually be
comparable to fluorescent.

TIR Systems is well known as a world leader in SSL and light pipe technology. They say that LED is
just a solid state light. What makes the difference is the housing/optics that determine the
efficiency of the lighting.

In fact, you should know VERY WELL that a number of factors affect a lamp's light output over time,
including lamp lumen depreciation, the lamp's interaction with the ballast, supply voltage
variations, dirt or dust on the lamp, and the ambient temperature in the fixture.

To avoid confusion, note that lumen output is a term used to describe a fixture's light output, not
just a lamp's. Even more factors can affect light output in this case, including the distribution
characteristics of the fixture, fixture surface depreciation, and dirt and dust buildup.

Check this one out..

tirsys.comcorporate whats new.aspOpen ↗ d=10

And you will see that you need your knowledge awareness updated.

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And I prefer sources that are truthful and unbiased.

That's why I referred you to my web site. Even if you disagree with the views of myself, and
others, regarding the level of lighting needed for commuting, the table of lumens and watts is not
based on any opinions.

Again, your website is just full of opinion with numbers conveniently picked out from every
convenient sources..

Lumens measurement made by who? The manufacturer or measurements by yourself?? Do you own a
Kyoritsu luminance meter and make measurements by yourself.. Hardly a source of reliable
information if all it does it organizes other people's opinions and misinformation in one rather
entertaining website I say.

"David" <[email hidden]> wrote in message
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Quoted message said:

For a typical cycle commuter, 1 hr for 5 days a week = 5 hrs/5 days. It means, a typical cycle
commuter will have to commute 500 days to kill the bulb. There are 365 days in a year, 1/4 of that
commuting during the long winter nights. So, it's really only about 90 to 100 days of the year
that you'll be needing lights. If it's 100 hrs per year use, that's 5 years. I think you'll find
that a LOT of people find this 500 hr limitation very acceptable indeed.

When the lamps cost $3-5 they find it acceptable. They can carry a spare. When a replacement lamp
costs $50, it's another story.

"rosco" <reverse-the-following"ocsor_g"@hotmail.com> wrote in message
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Quoted message said:

"B.C. Cletta" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"rosco" <reverse-the-following"ocsor_g"@hotmail.com> wrote in message

news:<[email hidden]>...

Quoted message said:

Quoted message said:

My Luxeon Star based flashlight (Surefire E2e w/ KL1 head) has *much* better optics & beam
pattern.

what's the beam like? any potential for bike use? whenever i'm ever feeling fiscally
irresponsible, i think about getting a SureFire KL-3 LED head, and adapting it for use bike use.
i wish they published beam pattern info. BTW, they a pretty good info section.

I'll try to take some pictures next week.

I took some pictures of the Planet Bike and Surefire beam patterns that I'll share if others are
interested. I don't have a webspace to post a jpg to, so if someone has such resources, please
contact me and I'll email you the picture.