By Ken James- Elberta, Alabama - USA
LED Navigation Lights
Ken James of www.firststarled.com
read an article in Duckworks about LED navigation lights and sent us this letter. We print it here with his permission.
I felt I must comment on your information about LED marine navigation lights.
Since nearly a decade ago now I was the first in the world to develop, manufacture and market LED marine navigation lights, the FirstStar anchor light and other navigation and cabin lights. I still make the most rugged, reliable, and efficient retro-fit LED light 'bulbs' today.
While I feel my lights represent a very good solution, I know others may want to tinker around... after all, that's how I got going! In 'light' of that <G>, I would like to point out several issues I see with the approach to a DIY LED multi color navigation light on your website.
First, using a 'white light' LED behind a colored lens or filter is inherently inefficient and will result in a dim light for the amount of light emitted by the LED, in fact it will be hard to get a light that is reliably visible at the required distance with this method. The reason for this is that 'white light' from these LED's is not really 'white light' as in from a normal bulb, but instead it is a light that is made up of mostly blue and yellow light but looks white to our eyes. This light will have as much as 50% absorbed by a green filter and 80% by red. The solution to this is to use colored LED's, then over 95% of the light gets through the filters.
But there is an even bigger problem with the usage you show. That is one of sector cut off or bleed over.
You do not want to confuse somebody as to what you are or what your heading or intentions might be with lights that do not show the proper color sectors.
The design you show can create just such confusion because the LED's will emit a cone of light coming from well on one side of each filter heading out of the fixture at an exit angle quite a bit off perpendicular through the center line, where it needs to be in a perpendicular direction at the center to assure no color overlap.
This usage as shown will instead create a lot of color overlap, so instead of having a crisp sharp cut off, as the rules require and as is needed, you will get a 'nushy' "zone of confusion" where the two colors will mix in large quantities producing a broad yellow stripe at dead ahead slowly fading to green or red.
This would happen even if the LED's were colored unless there was some optical element included or the LED's had a VERY sharp 'edge' of pattern emission and that edge was placed directly behind the center so they emitted straight ahead.
The aft sector sides won't be so bad as they will be just one color but will lack the crisp cut off needed.
Of course, a normal bulb gets around this overlap problem by using a very small diameter vertical filament placed in the center, but even so you will notice this "zone of confusion" to some extent on a bow combo red/green light. But a good LED based design can reduce that over what a normal bulb will produce.
All this is in addition to the fact that such lights based on a simple design that uses an LED array connected to a current limiting series resistor have NO over voltage or transient protection, and will become very dim at normal low battery voltages. These LED lights just were not designed for this critical application!
In sum the design is potentially dangerous because it can create confusion, will likely not be visible at anywhere near the required distance, is not reliable or robust electrically or physically, and will become dim early.
I would be happy to help any DIY'er to make LED navigation lights that will overcome all these difficulties. Just email me and I will supply whatever information etc. I can.
Or go to the tech page on www.firststarled.com for some information that may prove helpful to design your own LED navigation lights.
I know I won't sell everybody one of my LED navigation lights, some want to DIY, but at least maybe I can help keep folks out of trouble! -Ken