My missus is having some problems seeing things on the road now that she 
is riding her (motor) cycle home in the dark.
I was wondering how 2 of these things mounted beside the main light 
would go in terms of enhancing the "near field" illumination something 
in the order of 20-30 meters or so would be the upper limit of what I 
was hoping for, this is in addition to her existing light.
Aimed fairly downwards so as not to get in the face of other drivers.

Of course the 3rd one goes into a teensy torch with an A123 cell 
powering it ;->

Apptech wrote:
>>> They make the point that the radiation pattern and 
>>> focusability
>>> allows an even greater improvement than this over CFLs on
>>> terms of end user light.
>>>       
>
>   
>> Ah, so this would be a suitable bulb to use in desk lights 
>> or those stand
>> alone over-your-shoulder type lights. CFLs work horribly 
>> in those.
>>     
>
>
> Yes. It has a fairly brought angle (about 140 degrees 
> between half power points) and a somewhat fatter than 
> Lambertian radiation pattern which is appropriate for this 
> sort of use, so would be good for that sort of lamp as is 
> and could be lensed down. Increasing angle with lenses is 
> something that some attempt but which is largely not 
> successful. You can use other optical devices to do this. 
> Starting as wide as you want or wider is usually best.
>
> Alas the LED at present costs about $US25 (Mouser /100) or 
> if you must buy it from them Euro 25 :-) from somebody else. 
> About $US30/1.
> No doubt the volume price will be somewhat lower but it's 
> still rather dear. At even $US20 that's $2/Watt which is OK.
>
> It would make a nice "torch" :-). 6 x 2500 mAh NimH would 
> last for about 45 minutes with a good buck regulator. A 12V 
> 7AH SLA brick would last for 6+ hours. It would take a 10 to 
> 20 Watt solar panel to service it well with a 12V 7AH SLA 
> but would be a very very good lightbulb replacement.
>
> IF the life is guaranteed it's OK, but this is by no means 
> certain.
>
> Luxeon have a "lumen maintenance" specification which is 
> essentially a guarantee against degradation. The 10 Watt LED 
> has no lifetime data that I can find so far. Dome is 
> "silicone resin", which is a good start.
>
> Looking at a data sheet for some Seoul Semiconductor 20 mA 
> 14 degree 18,000 mCd LEDs revealed a disturbing fact. In the 
> test data they run them at 30 mA (the max rating) and test a 
> batch of 18 (it seems) for 1000 hours. The spec is for 0 
> failures in this time within test limits. Some parameter 
> limits are fine BUT the flux limit is 50%. So they are 
> saying that all LEDs in the test did not degrade by more 
> than 50% in 1000 hours. I would certainly hope not !!! This 
> limit is disturbing as they have obviously [tm] set it low 
> enough to ensure no failures in 1000 hours. That suggests 
> that  a limit of say 60% or 80% or 90% was too tight. With 
> lifetimes loosely quoted as 100,000 hours and real lifetimes 
> of 10,000 hours plus I'd certainly expect FAR better than 
> 50% degradation in 1000 hours, even at max permissible 
> current. .
>
>
>
>
>         Russell McMahon
>
>   

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