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Old 04-08-2007, 05:11   #31
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Quote:
Originally Posted by 44'cruisingcat
The link didn't work for me
it works for me, but it is at alpenglowlights.com
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Old 04-08-2007, 13:46   #32
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Hellosailor, my boat is a multihull, with a heel angle of about 12-15 degrees, but even a "leaner" usually isn't too much more than that. In big seas, the wave height will often obscure the deck lights, less likely a masthead unit. Since I am only concerned with another vessel seeing my nav lights on the horizon, all of those factors you expressed are resolved by the manufacturer, Dr. LED. I suppose an airplane or satellite passing overhead might have some difficulty making out my bearing, but I am not overly concerned. Aquasignal's bulb base curiously matches the alignment of the color sectors of the tricolor LED bulb I use in my masthead running lights. Do you suppose they do this purposely? In my cockpit nav light switch, I use a waterproof on-off-on switch to select between masthead LED running lights under sail, or incandescent deck lights for power. It allows me to not worry about energy consumption during a long night's passage, or having to go to the masthead to change out a bulb. The deck lights are easy to get to, and allow me to use up my spare series 40 bulbs while I'm generating electricity.

Additionally, I use low intensity red LED lights as my "night lights", illuminating the companionway steps, the head floor, the galley counter, and some other locations that I need from time to time during the night. They are switched from the cockpit so I can pop down into the cabin without waking the offwatch. Since the power drain is negligible, I'm even considering placing them inside my floats and deck hatches to make it easy to check out the boat on my occasional night inspections. I love these things. I'm also going to install some high output white LEDs near my seawater impeller pump so I won't need to hold a flashlight while making inspections. The number of potential uses just keeps growing.
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Old 04-08-2007, 15:00   #33
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Yes dry cells run down, but their peak power is totally limited . There is no chance of a spike.
Will low voltage kill an LED? That in itself would make them unreliable.
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Old 04-08-2007, 18:40   #34
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Ooops I haven't been following this thread. So sorry if I am going over what someone has already stated.
LED's a Current devices. Not voltage. You can have any voltage (within reason) but the current must be the required amount to operate the LED. Voltage pulsing was found to be a way of increasing the brightness of an LED without losing to much of it's life. I am not entirely sure what they do, but it seems to work.
Back to the current thingy, the LED requires a certain current to illuminate. Once it has reached full output, and additional current supplied simply produces heat, not more light. Eventually the LED fails. A resistor is a simple current shunt. In other words, current is lost across the resistor as heat and the rest is what powers the LED. If the current is low and the LED dull and then the current is raised the LED will illumiate brighter. Till the point of max current draw of the LED. Once it reaches max output, the resistance of the LED starts to brick wall. The resistor has to disapate more current as heat untill either devices finaly fail.
An electronic regulator is a clever way of giving the LED max light output with the least current being disapated as heat. A good regulator should be far more robust and more fail safe than a simple resistor.
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Old 04-08-2007, 21:22   #35
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Roy, I'm all in favor of LEDs. Although, personally I'd probably use amber (aka yellow) instead of red below. If the ones you use in your nav light are sufficient to do the job--that's all they need to be. My point is just that they are neither simple nor universal replacements for all users and all cases. But then again...those "perfect" tungsten bulbs are also guaranteed to burn out at the least convenient moment.<G>
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Old 04-08-2007, 23:26   #36
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Is there a specific reason for amber and not red??
I was thinking of a Red led light for my night light in the Pilot house. My thinking was the more "pure" red from the LED may be better than a red bulb.
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Old 05-08-2007, 01:35   #37
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Executive Summary: LEDs with properly-designed regulators are reliable and efficient.

Quote:
Originally Posted by Louis Riel
Yes dry cells run down, but their peak power is totally limited . There is no chance of a spike.
Will low voltage kill an LED? That in itself would make them unreliable.
brent
Low Voltage will not kill an LED, it will just reduce the light output when using simple resistor regulation.

The trick with resistive regulation is that you don't want to throw away any more power than necessary, so you are tempted to design for the nominal battery voltage. Unfortunately this means that you are running too much current when the battery is fully-charged, and the light quickly dims as the battery depletes. This can be a problem even with dry cells, as you saw with your cheap flashlight. You can minimize the variation, but at the expense of efficiency.

This is why better designs use active regulation, which can hold the current through the LED constant, or even compensate for temperature variations. This gives you much better overall efficiency, reliability, and steady output.

There are different types of active regulators (switching or linear), with the switchers being more complex but more efficient. Any of these should be at least as reliable as the LED itself.
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Old 05-08-2007, 10:55   #38
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Alan, I believe the reason for red lights over amber has to do with the response of the rods and cones in the retina. It's been awhile since I studied optical anatomy, but I recall that the red doesn't leave a "memory" image, and that anything on the spectrum that is beyond red causes the pupils to contract, making the observer wait for a period of time to adapt to low light levels. Besides, it makes me think I'm on the bridge of a ship.
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Old 05-08-2007, 14:00   #39
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Thanks Roy, yes I understand that. It was the amber I didn't. I was wondering if the amber was something I had missed, but I suspect the Red would be better than the Amber.
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Old 05-08-2007, 17:15   #40
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The choice of light color is somewhat personal. Some military night lighting is amber-green, no longer red. Among other things red is supposed to turn on the adrenalin, not a good thing to waste unless you need it. The red is perceived by the "colorblind" night vision parts of the eye, but the amber comes close to the spectral range where your eye's color vision is MOST sensitive, so you can use low levels of amber (or green) light and because the level is low enough--not affect the night vision.

Technically the eye is most sensitive to an "amber-green" section of the specturm, so there's still debate over which way (amber? green?) to go.

It is cheap enough, and easy enough, to buy a dollar's worth of each color and see which ones suit you best, personally. And which ones give you "some" color perception, as well.

You'll notice a few car dashboards are lit up with red lights--supposedly for better night vision. But most use a greenish color, and with the dimmer...the funny thing is, it does work just as well. Without triggering any mental response to red.
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Old 06-08-2007, 03:24   #41
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Total brightness, or illumination level, of the light has a potentially more significant effect on night vision retention than does the choice of colour. Choose the dimmest light, which will do the job. The brighter the light, the more negative impact on night vision - both in our capacity to see, and in how long it takes recover optimum night vision. This is true regardless of the colour of the light source.

For the reasons Roy M & hellosailor suggested, amber or green night lighting is probably the most efficacious choice for tasks requiring visual acuity & colour perception (chart reading, etc):

It takes a while for true night vision to be recovered after exposure to light . About 10 minutes for 10%, 30-45 minutes for 80%, the rest may take hours, or even days. The issue is the chemical in the eye, rhodopsin - commonly called visual purple, is broken down quickly by light. The main issue then is intensity; color is only an issue because the rods (responsible for night vision) are most sensitive at a particular color. That color is a blue-green (507nm) similar to traffic light green . It would seem that using the lowest brightness (using this color) additional light needed for a task is the best bet to retain this dark adaptation because it allows rods to function at their best.

There are three operational modes of vision; photopic, mesopic and scotopic.

Photopic (day) vision occurs at high light levels and is characterized by:
(1) heavy dependence upon cone photoreceptors
(2) low light sensitivity
(3) high visual acuity
(4) color vision.

Mesopic (twilight) vision, which is a state of photoreception where the bottom of cone and top of the rod operating levels overlap.

Scotopic (night) vision occurs at very low light levels and exhibits:
(1) use of cone photoreceptors
(2) high light sensitivity
(3) poor acuity
(4) no color vision.

Some excellent reading:


Surviving the Nightshift - Low Light Visual Adaptation
Surviving the NightShift III

Night Vision ~ by Marc Green
Visual Expert Human Factors: Night Vision

Seeing Red - Astrolights for Visual Work ~ by Doug Kniffen
Doug Kniffen's Green Astrolights

Human Vision and Color Perception ~ by Michael W. Davidson, Mortimer Abramowitz, Olympus America Inc., and The Florida State University
Molecular Expressions Microscopy Primer: Physics of Light and Color - Human Vision and Color Perception

Light and Dark Adaptation (Psychophysics of Vision) ~ by Michael Kalloniatis and Charles Luu
Part 9, chapter 4 of WebVision - an online resource that describes the nerve cells and functional pathways of the vertebrate retina.
Webvision: Light and Dark Adaptation

NIGHT VISION ~ Search and Rescue Society of British Columbia
SARBC - Night Vision

Green or Red for Better Night Vision?
EQUIPPED TO SURVIVE (tm) - Green or Red for Better Night Vision?

Night Vision - The Red Myth
Night Vision - The Red Myth

The complete WebVision site: Webvision Home Page
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Old 06-08-2007, 12:22   #42
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Nice research Gord!
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Old 07-08-2007, 03:35   #43
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Have just got back from my boat.... turned on the lights...and guess what....they all worked !! Oh by the way they are home built LEDs and they have been in service for five years. They have not been touched since they went in. Nav lights Deck mount Port / Starboard , Stern and red over green top mast, Anchor light , and interior lights. The only other light I use is a small fluro if I need a bit more brightness. With all LED lights on (in and out) and the radio (music) I draw half an amp. Thats why I like LEDs !!
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Old 13-08-2007, 07:36   #44
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Have been using a LED Xmas lights set in the garden at night powered by a 12 volt car battery. Works fine and can regulate the flashing as well. Very cheap way of creating a stylish lighting scheme in a boat. XPeriMental.

Give it a whirl.

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Old 13-08-2007, 13:59   #45
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LED's are great, but IMHO they aren't very good for reading yet. I just bought a bunch of CCFL's which I think are much more suitable. The "marine" ones are quite expensive, but you can get these Super Bright White 12" Dual Tube CCFL Kit that the computer geeks put inside their computers for real cheap, and they run off 12V.
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