The heat argument is a little misleading. These LEDs don't generate
much heat only because each unit consumes a mere 65mW. With 240 devices
they will be dissipating a lot of heat. Lamps are measured by luminous
efficiency. At 20-deg beam angle, 30000 mcd is equal to 2.8 lumens. So
the luminous efficiency is 43 lumens/watt. For comparison, fluorescent
lights are about 50 lumens/watt, and some HID lamps are 50-100
lumens/watt.
In addition, with 240 devices packed in close proximity, the efficiency
is unlikely to be the same as a solitary device. I would guess it would
be around 25 lumens/watt, in which case you will be pretty close to the
Luxeon V LEDs.
--- rparigor@suffolk.lib.ny.us wrote:
>
> Hello Ira
>
> Not going to OSH this year.
>
> Its true 5 watt LEDs need great cooling. The LEDs I am proposing are
> not
> drawing 700 mAs each, but 20 mAs each. Heat is not a problem with
> even
> continuous use. That said, many new 5 watt LEDs as offered by Best
> Hong
> Hong live on a fairly large star of aluminium (heat sink) and that
> aluminium can live on a piece of conductive metal.
>
> Its true that my idea of a removable landing/taxi light could
> possibly be
> accomplished with some 5 watt LEDs with a 10 degree reflector, could
> put
> in a tube in same area under cowl, and have some air pass through,
> larger
> bump, a lot more heat and a lot more amp draw.
>
> There is no question that a Beechcraft 100 watt, I think 5+1/2"
> landing
> light does a great job. A 3.5" Cessna 100 watt does a good job. A
> 3.5"
> Halogen Cessna 50 watt 3.5" does close to the net usable of the 3.5"
> 100
> watt.
>
> 100 watt lamps, and 50s make heat, and lots of it, not great for
> composites. Where do you put one on a Europa?
>
> I am proposing a field of approx. 10 square inches of 20mA LEDs, ~240
> 10mm
> 12 degree 20mA, and between them ~60 5mm 20 degree 20mA. It will not
> light
> up a path wide enough or forward enough for landing C-130s at
> Gabreski,
> but probably adaquite for a Europa to do a low pass to see if there
> are
> any deer on Gabreskis runway, and see well enough for take off,
> landing
> and taxi.
>
> The arrangement does not need to be square, it can conform to shape
> of
> lower airscoop of cowl, narrow and long, will be adding bout
> thickness of
> a finger to the cowl. Again only take the increase drag when you need
> lights, and it will work on both short and long wings.
>
> I have LEDs at hangar, come on over one night and tell me what you
> think.
>
> The Net light output of the 10mm LEDs I want to use supposedly
> require
> only 1/5th the power in compared to Halogen lamps. Can put 4 or 5 in
> series when using ships power.
>
>
> Ron P.
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
Andrew Sarangan
http://www.sarangan.org
|