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Re: [EVDL] LED Taillights - a money saver in gas cars? -rangeextenderin EV's? - an an

Danny Miller wrote:

> A 3W red Luxeon sounds excessive for a taillight.

Yes, I was looking at the 1157 replacement. It uses the Luxeon at a
much lower power level for the tail lights and full power for brake

> Lumens are different in 2 ways. First off a white taillight bulb may
> produce 400 lumens of white, but the red filter only makes the
> light red
> by blocking more than 2/3rds of the light energy because the blue and
> green components are useless (a filter does not change photons of one
> wavelength into another).
> Then the bulb throws those remaining lumens at 360 deg. Half will
> strike the back, which may be silvered so at least some of it will end
> up getting thrown forward again.

A couple of very good points. I may get as much red light out the
lens with 240 lumens of red LED with a 130 degree spread as I can get
with a 1157 bulb. The question becomes how much of the light from an
incandescent tail light is wasted. Car tail light bulbs are generally
"warm white." Just how much is red, and how much the reflector
looses, are questions I haven't found any documented answers to.

> It is possible for an LED to be excessively bright only in the center.
> Even in "wide" spread LEDs, like 130 deg, the intensity is greater
> straight ahead, decreasing substantially as angle increases. This can
> result in a very bright spot projected onto the middle of a
> taillight lens.
> Multiple 7.6mm P4 pkg are a really good option. They get used a
> lot in
> commercial taillights. Since the pkgs can be spread out, they won't
> make a single bright spot. There's also far less thermal issues when
> it's done this way.

There will be no cutting up of '66 Datsun tail light assemblies!
Either it works acceptably well (equally bright, not to directional,
not to "spot light") or I put the 1157 bulbs back in. I have looked
at LED bulbs for it, but its not the current priority. Its a garage
ornament at this time and that needs to be taken care of before I can
really rate the effectiveness of LED bulbs for it. (real world with
my wife following me)

Paul Gooch

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