Lights: LED vrs. Halogen?



On Sep 6, 1:19 pm, Dylan Smith <[email protected]> wrote:
> On 2007-09-06, [email protected] <[email protected]> wrote:
>
> > Ahh, I see now that the MR11 are HID. But at those low powers they're
> > much less efficient than LED. What they will have over LED is the
> > ability to focus into a much tighter beam.

>
> Surely that depends on the reflector and lens, rather than the bulb?
> Especially since you've got single LEDs rated at 4 watts these days.
>

Not really, High power LEDs achieve their high power rating by having
a large die area. So they don't even approximate to point sources. (I
guess one of the problems with making high power LEDs is avoiding hot
spots on the die). Therefore regardless of what lenses and reflectors
you use the beam is going to have a high(ish) divergence. (You can, of
course, create a beam with a low divergence by putting the source at
one end of a long matt black tube but you then achieve the low
divergence by throwing most of the light away.

Tim.
 
A

Alan Braggins

Guest
In article <[email protected]>, [email protected] wrote:
>There is a limit to the brightness you can get from a single LED - the
>Cateyes mentioned in the other thread (there are slightly newer/better
>ones than the EL500) are pretty much state of the art in this respect.
>[1]


If brighter means better, the Cateye Triple Shot is much better than
the EL500, not just slightly. But much more expensive.
Or, with a lot of work, you can build something like
http://www.enhydralutris.de/Fahrrad/LEDWerfer0402/#2

The EL530 might be pretty much state of the art for a compact 4-AA LED
light, but you can do much better (for some values of better).


>Multi-LED lights can be very bright but they won't give a good beam
>because the light source is spread out.


Multi-LED lights where each LED has its own optics can give just as good
a beam. And still be fairly compact, e.g.
http://www.ghostgum.com.au/misc/BikeLightV2.htm
Again, massively more light than a 4-AA Cateye like the EL500 or EL530.


>If you want something brighter (better beam) than a single LED light,
>look at what MTB riders use at night. Their requirements are rather
>different to road riders - they want extremely bright light but for
>short periods of an hour or two.


Some of them want light for all night endurance racing.


> They get this with largeish
>rechargeable batteries and halogen lights.


Or LEDs, like the USE Exposure, or Solidlights 1303 (or Cateye Shot).
Or HID, like the Cateye Stadium, for even more light.
 
A

Alan Braggins

Guest
In article <[email protected]>, [email protected] wrote:
>
>The highest efficiency high-power white LED is claimed by Philips
>Lumileds Lighting Co. with a luminous efficacy of 115 lm/W (350 mA).
>
>(Of course, 1W is considered high power in LED lighting.


The same Lumileds press release says 61 lm/W at 2000mA/8.3W

So they will run at significantly higher power, approaching the
HID low end, but efficacy drops off. And heatsinking gets really
really important.
 
D

Dylan Smith

Guest
On 2007-09-06, [email protected] <[email protected]> wrote:
>> Surely that depends on the reflector and lens, rather than the bulb?
>> Especially since you've got single LEDs rated at 4 watts these days.
>>

> Not really, High power LEDs achieve their high power rating by having
> a large die area. So they don't even approximate to point sources.


I haven't looked at the most powerful LEDs, but I have some 1 watt
Luxeon emitters. The apparent die size, even through the convex lens
(which will make it appear larger) only is around 1mm square. The
halogen bulbs I've seen all have filaments probably 10 times this size.

So surely an LED is more of a point source than a halogen?

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de
 
T

TimHenderson

Guest
On 6 Sep, 09:17, Peter Clinch <[email protected]> wrote:
> Artemisia wrote:
> > What lights are brighter, LEDs or halogens?

>


> I have a LED B&M Oval on the Streetmachine, and it's IMHO a little
> better than the (nothing wrong with it) Halgen I used to have, but I
> don't need to carry a spare bulb.
>
> Pete.


I like the sound of the latest offering from B&M - see the Lumotec IQ
fly under innovations at
http://www.bumm.de/index-e.html
 
M

Mike the unimaginative

Guest
Artemisia <[email protected]> wrote in news:1189061483.993980.119390
@r34g2000hsd.googlegroups.com:

> What lights are brighter, LEDs or halogens?
>
> For some reason, I can't find LEDs on sale in France. Only halogens. I
> have to get my lights through the UK which seems daft. Is there some
> stupid protectionist law in place?


I was in The Netherlands (Leiden) a couple of weeks ago, and although I
wasn't specifically looking, I don't recall seeing anything except LEDs on
sale
 
L

Larry Farrell

Guest
On Sep 7, 8:55 am, Larry Farrell <[email protected]> wrote:
> [email protected] wrote:
> > On Sep 6, 10:57 pm, POHB <[email protected]> wrote:
> >> On 6 Sep, 10:44, [email protected] wrote:

>
> >>>www.ayup.com.auwillsolve your problems. Fine lights
> >> Fine lights maybe, but the most irritating unusable website I've seen
> >> for ages.

>
> > Yes, I have to agree. Even less fun with a slow connection. Persevere,
> > it's worth it.

>
> I got "Server Not Found" repeatedly.
>
> --
> Posted via a free Usenet account fromhttp://www.teranews.com


Looks like the link joined to the next word. Try this
http://www.ayup.com.au/
 
M

Matt O'Toole

Guest
On Wed, 05 Sep 2007 23:51:23 -0700, Artemisia wrote:

> What lights are brighter, LEDs or halogens?
>
> For some reason, I can't find LEDs on sale in France. Only halogens. I
> have to get my lights through the UK which seems daft. Is there some
> stupid protectionist law in place? I've been following the other
> discussion on lights and think I may get that Cateye HL-EL500 so
> highly spoken of, for the trike, in addition to / instead of the
> dynamo.


I have an older Cateye Halogen, the HL-500 Micro, which is still
better than the newer LED models like the HL-EL500. LEDs may be more
efficient than halogens, but a 1W LED still can't compete with a 2.4W
halogen.

I once borrowed an HL-El500 to ride home from a friend's house, and found
it woefully inadequate. I couldn't see the curves in the road, almost ran
into parked cars, etc. The beam is bright but too narrowly focused to be
useful.

Battery life is moot when you're using rechargeables, which you should be
using anyway.

3-5W LED lights are great, but expensive.

Matt O.