LED headlights?

Steven M. Scharf wrote:
optics improve, then LEDs may have a future in high brightness bicycle
lighting. For now, they're "being seen" lights only.

That's odd; when we started, you thought that one needed bright lights to
be seen in urban situations, and in the country weaker lights would
suffice. What changed?
--
David Damerell Kill the tomato!

"B.C. Cletta" wrote in message
om...
"rosco" wrote in message
ink.net...
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.

(B.C. Cletta) wrote in message . com...
"rosco" wrote in message ink.net...
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:
http://elektrolumens.com/Tri-Star-Bike-Light/Tri-Star-Bike-Light.html

"Steven M. Scharf" wrote:

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.

http://www.lumileds.com/luxeon/products/star_index.html

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

On Sat, 10 Jan 2004 10:40:39 -0500, David L. Johnson wrote:

Following some of the advice, I*ordered the Planet Bike Super Spot 1W led
light. Unlike someone else on this thread, I think I will keep it. No,
it is not as bright as my nightrider. I just went outside to compare
them, and the LED was useless beyond say 10 meters, while the
nightrider still would illuminate the road well beyond that distance. But
the LED was certainly bright enough to illuminate the road up close, so
you could use it to see if needed, at a slow but reasonable speed. And it
definitely was enough light to be seen under any conditions. Certainly
useful as a backup, especially if it gets the 30 hours run time it claims.

--

David L. Johnson

__o | the people can always be brought to the bidding of the leaders.
_`\(,_ | That is easy. All you have to do is tell them they are being
(_)/ (_) | attacked, and denounce the peacemakers for lack of patriotism
and exposing the country to danger. It works the same in any
country. -- Hermann Goering

"Chalo" wrote in message
om...

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.

http://www.lumileds.com/luxeon/products/star_index.html

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 wrote:


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.

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

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"]

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.

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.

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.

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..

http://www.tirsys.com/corporate/corp...tion=details&i
d=10

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




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" wrote in message
hoo.dsafds.com...

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" wrote in message
ink.net...

"B.C. Cletta" wrote in message
om...
"rosco" wrote in message
ink.net...
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.