Interesting use of Luxeon in Runway Lighting.

Just tripped over an interesting light fixture at work. Spotted a runway lighting fixture sitting on a shelf that appeared to have some electronics in it. These usually have halogen lamps in them at about 50-80watts. So I looked closer. It has two little heads pointing each way, that have SE Luxeons in little (1.2" or so) reflectors!

This fixture is designed to be set into the runway so the pilots can see the various 'lines' when landing. I think this was a centerline light. Looks like an iron frizbee with an aluminum sour cream container underneath. 747's nose wheels land on these.. They run off of a 6.6amp constant current loop. The electronics obviously converts this to something tastier for the Luxeons. I'm going to try to borrow this and play with it a bit. Bound to be interesting. Can't tell yet what wattage they are..
Anyone else ever seen something like this? Really nice little reflector assys..

Yours, drs the crazed. /ubbthreads/images/graemlins/grin.gif

Seen a few people go for airfield lighting with LEDs, looks like the ideal application for resitance aginst vibration and sudden shock loads, like a 747 landing on top of it.

What I don`t fully underestand is the use of constant current loops for feeding the lighting, what is the advantage?

thanks
Adam

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LED-FX said:
Seen a few people go for airfield lighting with LEDs, looks like the ideal application for resitance aginst vibration and sudden shock loads, like a 747 landing on top of it.

What I don`t fully underestand is the use of constant current loops for feeding the lighting, what is the advantage?



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I'll have to ask again, but I'm pretty sure it has to do with cable length and voltage drops. (Some of our cables are 8 miles+) simplicity in wiring and maintenance, and the ease of using low voltage bulbs. (Heavier, sturdier filament so those nasty airplanes don't jar 'em loose..;-)
Constant brightness, too. (Like the Milkycandle /ubbthreads/images/graemlins/grin.gif

The wire size'd have to be amazing to get the power out there. We have up to 75KW regulators. Lots of juice. Each lamp, tho, eats between 3V and 12V at 6.6A. And yes, they do have tricks like shorting lamps and 'pills' etc, to keep the string lit. Works pretty good. Wouldn't mind having many thousands of Luxeons to play with, either. (Not on the airfield, tho. BIG no-no!)

Back to my pile o' project..

Yours, DRS the crazed

Talked to the guy in charge of the item in question. The one I was looking at is a infant mortality failed sample. Three more are out there running fine. (Taxiway centerline. Green SE Luxeons. Don't know the rest... Yet.... /ubbthreads/images/graemlins/naughty.gif

He let me hook it temporarily. I'll check it out, try to figure the failure mode, and play with the bright, shiney things.. Will post pix of the guts when I get a little time. Has a 6.6A converter in it, with a microcomputer and some switches and stuff, so I'm rather curious..

Considering that each pair of luxeons is taking the place of a 62 watt halogen (With a green filter, tho), it's probably rather potent...

Looking forward the messin'!

Happy Holidays!

Yours, DRS the shineyaddict..

Pictures, pictures, pictures!!

Very interesting design based on constant current loops. There is a similar advantage when using 4-20mA process control loops. Voltage drop due to cabling or sensor power "stealing" does not affect the accuracy. the high current I am guessing is so the halogen lamps can be low voltage yet high power. If all the lamps were LED, a much lower current could probably be used.

My first guess is that a shunt resistor is used to bypass much of the current (and provide fail-safe operation for the entire loop) and the resulting small voltage drop is used to drive a regulating converter operating the LEDs.

DRS: PM sent...

The only approved LED's for use on the airfield are for obstruction and taxiway lighting. LED doesn't put out the intensity required for most all runway lighting situations. The FAA is currently testing LED fixtures for cenerline lighting as well as runway edge lighting, but the required intensity just isn't quite there.

Any LED fixtures DRS has found are a test, possibly by the FAA. I have two LED Taxiway lights at my desk as well as an LED obstruction light. The obstruction light is bright as hell, and is loaded with 1W red Luxeons. The taxiway lights I have are a 6.6A and a 120V version. Obviously, I don't have a power source for the 6.6, but I do for the 120. I use it to light up the air vent above my cube.



Keep in mind, that is directly next to a fluorescent light fixture and our office is VERY well lit. That will give you an idea how bright it is.

6.6 Amps is a standard for airport lighting and each circuit is run off a CCR (Constant Current Regulator). The regulators are used (as DRS thought) with the 6.6A due to the miles of cable that may be on one circuit and the resulting voltage drop. I just completed the design of the lighting, signage, and pavement markings for a large airport. The runway is over 7000' long, with at least 4 different circuits and systems for runway lighting alone.

The LED taxiway lights are primarily being used to extend existing circuits without putting a large enough "new" load on the CCR to warrant upgrading it to the next size. I suspect my next job (which happens to have about 4 miles of new taxiway) will incorporate the new LED taxiway lighting so long as the client likes it.