I've been considering LED side lights but don't find any suitable for a
sail boat. Is this because they are too directional or what?
Gordon
"greenrayled" wrote in message
...

Ah, now I understand. But this has no benefits. A LED that is
continuously
on at, say 20mA, will appear to have the same brightness as when
strobed
with a 20% duty-cycle (1/5 of the time) at 100mA (5 times the
current).

Meindert



Actually not quite. If you talk energy consumption then you are
right.
But you can viciously overdrivve LEDs to get far more brightness out
of then than they normally can give.

There is also argument that your eye and brain think that the led is
still alight and this can fool you into seeing a brighter LED. I
would
reckon this would work best for LEDs being looked _at_, rather than
thiose used as a source of illumination.[/i][/color]



I have been designing such pulse driven led lights commercialy for over
seven years. I have designed and made (still make) all the various LED
navigation lights, including anchor lights, and cabin lights too, but
some of the cabin models are not pulsed...pulse drive works better for
*visibility*.

Yes, pulsing can increase PERCIEVED brightness, if the correct paremeters
are followed, it is a well documented human perception phenomena. You
don't really need to "overdrive" the leds either, just stay within their
temp/current ratings for a given duty cycle. The led driver I use now
takes into account input voltage, temperature, and type of led used, and
without ever pushing more current through the led than it was designed to
handle it produces a pulse train of a frequency, output voltage, and duty
cycle such that from a very low voltage to a very high voltage (input)
the led will be at a relatively uniform percieved brightness for a power
consumption of about 60% of that required to get similar percieved
brightness from continusly driven leds. Pulse driving with a carefully
controled variable pulse is by far the most efficient way to get maximum
percieved brightness, as not only do you utilize the inherently efficient
design of switching control (either on or off, no wasting of electricity
by turning it into heat) but you can take advantage of the perception
factor and get a further boost in performance that makes this design
concept superior.
The led nav light drivers I design also incorperate such features as
transient, spike,and overvoltage protection, (I have tested the 12VDC
light on 115VAC, it shrugged it off) day sensing, bi-polar operation,
ect. into retrofit-able led 'bulbs', with the result that when used in a
standard fixture they give the same or often even better visibility than
the normal incandesecent bulb that they are designed to replace, IE
greater than 2NM visibility, but with better functonality, features, and
reliability. In fact, they are about as bright as other newer model led
anchor lights that use a DC-DC converter to drive their leds, but the
pulsed model uses only a small portion of the power that the DC-DC model
does. I have reasonably good pictures taken at night with a digital
camera that show pretty close to what the eye sees, comparing anchor
light fixtures containing both incandesecent bulbs and continuously on
leds with the pulsed model that bear this out.
A normal boat could anchor, turn the anchor light on, go away for the
summer, and come back and start the engine in the late fall with no
worries.

If anybody would like more information about led boat lighting design, I
would be happy to send some to them off-list...it is kinda long. I can
get carried away. ;-) -Ken


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greenrayled[/i][/color]