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From: Ken James (no email)
Date: Mon Apr 07 2008 - 01:09:14 EDT
Kris Coward wrote:
> On Sun, Apr 06, 2008 at 08:56:23PM -0500, Ken James wrote:
>
>> Here is a brief explanation of why buying a 20$ LED light is not a good
>> way to get the most for your money, and why buying a light that is more
>> expensive "up front' can give you much more light per dollar.
>>
>
> Yes, but buying a pre-fabricated LED light, regardless of price, helps
> avoid the headaches associated with temperature and moisture management
> when designing your own LED light with high-end LEDs, or at least that
> was the opinion I formed when back when the X-Lamp first exceeded CFL
> efficiency.
>
But that is part of my point...there already ARE prefabricated such
lights that use the new LEDs!
(I am not familiar with the X lamp, but only recently have LEDs become
more efficient than CFLs, and the LED that accomplished this in spades
is the Lumiled Rebel, top in the wold right now and far, far ahead of
cheaper LEDs.)
> Ideally, I'd love to have bulbs consisting of 6-LED arrays, using the
> high-intensity, high-efficiency LEDs, angled slightly away from each
> other to get good broad coverage, run 3 to a series on an efficient
> enough voltage regulator to keep them at 350mA under any non-depleted
> charge condition of my batteries.
You don't need six of these LEDs to get more light than ANY normal boat
incandescent fixture. Just ONE of these LEDs can make as much light as a
20 watt halogen bulb, and the larger model of these Rebel LEDs can make
more light than a 60W bulb (some are now being used as car headlights).
Making a single light fixture too bright is not a good idea anyway as it
makes too much 'glare'.
Also, you don't need to angle the LEDs as they will make a 140 degree
beam pattern, or that is wider than most fixtures can use.
Many efficient driver designs, such as dc-dc conversion switch mode, do
not require the LEDs to be connected in series. And the best way to
drive the LEDs is NOT with a voltage regulated driver, as if you do that
as the LEDs heat up they will draw too much power, a constant current
driver is a better choice, but then you must allow for the effects of an
LED opening or shorting.
Also, with the new LEDs, thermal considerations become critical, if
these are not taken into account the design may well fail prematurely,
even though these LEDs themselves can take 350 deg F.
I use a propriety variant of a pulse width modulation driver, I call it
Variable Pulse Width design or VPW and it sidesteps many of the issues.
It has transient, over voltage, and over current protection, and short
circuit protection on both input AND output built in, and LED array temp
feedback built in also as well as being an extremely efficient almost
constant current switch mode type of driver that makes NO RFI or EMI.
It is very tough and compact and makes almost no heat.
> All this suitably housed to prevent
> any thermal or moisture problems,
The lights I make are potted, better models of lights similar to mine
are also coated and or potted, so moisture is not a problem.
> attach to the light fixture I want to
> use, and take the already reasonably broad light pattern, and spread it
> even more evenly (I'm willing to accept some loss of luminosity to get
> this,
No loss occurs with the new Rebel LEDs, they have an amazingly uniform
light pattern that needs no 'spreading' at all.
> so a solution like shining the light at the back side of a piece
> of paper is fine with me).
>
But right now, I'll acknowledge that this IS too much to ask for,
NOT AT ALL, variations of such a light that can EASILY fulfill ALL your
requirements of luminosity and beam pattern, as well as choice of color
temps, color selection choices of red, blue, green, amber and others,
very high level of electrical protection, fully sealed and potted for
environmental protection, super high efficiency, dimming function, and
un-equaled compact size is available right now.
Several manufactures offer such lights (I am one).
And these lights will make a good deal more light for the $ than the 20$
lights. -Ken
>
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