On Sat, 26 Jul 2003 11:39:53 +1000, "stu" <
[email protected]> may have said:
>>The reason this works is that with a 3W conventional bulb, only about one quarter of the energy
>>used (at best, and generally much less) is converted to light; with an LED, it's more on the order
>>of two-thirds.
>LEDs and quartz halogen have about the same lumens per Watt.
My lightmeters disagree. The comparison is more like 3 to 1 in favor of the LED, compared to 6 to 1
for a conventional incandescent. This is taking readings from several angles and averaging them
together. The data in one of the LED manufacturers' spec sheets suggests that my estimates are off
by a good bit in the halogen's favor, but I'll take mine. They suggest a ratio that seems absurdly
good; the halogen would have to be using less than 4% of its energy consumption for light production
for the figures to be correct, and I think that's probably a bit low.
>Leds don't needs as much focusing because most of the light comes out the front anyway.
Good news and bad news there; the beam *can't* be focused very well by the use of additional
reflector elements; the lens is all you have to work with. This isn't optimal by any means.
>So for a nice wide beam they work great. If you want a pencil beam you will have trouble. and for
>the same sort of output you are talking lots of $.
Higher than incandescent initially, yes, but cheaper in the long run in appropriate
applications...and frankly, the site you mentioned is horribly overpriced. I can get many of the
same items locally for about one third of those prices. Not everyone knows where the stuff is
available, so they probably get a lot of business from folks who just don't know of any other
source. Many of the local truck lines have entirely swapped over to the LED tail and signal lamp
assemblies because the price for that long-life unit is about half the cost of the conventional unit
with two years' worth of maintenance added in.
>See MR-16 about halfway down the page only $80each(l think you would need about 4 of them to
>replace a 15W halogen)
http://www.theledlight.com/dcbulbs.html and there figures are a little umm
>misleding (leading get it)
>>60mA at12vdc; 180 lumen; approximately 15 watts.
>the 15watts they are talking about must be an incandescent bulb, which is a little misleading being
>that it is a replacement of a halogen bulb
The lumens thing is also a bit difficult to make a comparison on; the halogen bulb's output can, at
this point, be utilized more efficiently with reflectors that are already well understood and in
production; if, however, the lamp assembly is designed for the LED light source, useful illumination
levels which are comparable to those from halogen bulbs can be achieved with less than one third of
the power consumption of halogen, just nowhere near as cheaply. On the other hand, the LED assembly
will be far more reliable. There are tradeoffs everywhere.
>some more interesting stuff on LEDs
http://www.theledlight.com/ledbulbs2.html
What they don't say (probably since I doubt that they know) is that white LED units with a
brightness adequate for automotive headlights should be in mass production within the next 6 years,
and should appear in automobile and truck applications soon thereafter. There are fundamental
headlight design issues which must be addressed, and it is considered unlikely that a DOT-approvable
LED conversion for existing headlamp bulbs will be marketed anytime soon, if ever. On the plus side,
it's not expected that the LED headlamps will be anywhere near as hideously expensive as the
high-frequency Xenon strobe units that are currently available. They very well may reach the level
of standard equipment on low-end vehicles within 10 to 12 years. Since it's likely that the average
LED headlight will outlast the car that it's delivered with, they probably won't be something that
you'll find on the shelf at every parts store.
--
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