LED Lights

[Cal Breed]

Anyone used the LED bulbs to replace the halogen bulbs for track lighting? They are pricey, but last forever and use very little electricity. I am worried about the color of the lights looking wierd like a headlamp light and affecting the look of the glass it is lighting.
Cal

[Tom Fuhrman]

I believe that the LEDs are being produced in different colors. It may take some hunting but I've read where they are available in the standard incandescent color, i.e. 2800K, and in many other colors up to 5500K, which is getting close to daylight. It may take a combination of different colors to make it look the best, just like using different colors of fluorescents. See if you can get the specs on the CRI, color rendering index, on whatever you decide to try. Be aware that CRI is not always the best indication of how things will appear when displayed. Some appear better in what we normally see as incandescent lighting and some in what we refer to as daylight lighting. The beam spread angle on these will also have a major effect on what you are trying to illuminate and the amount of light you get on the piece. I think the standard MR-16 or MR-11 12V track fixture with an open back will still give some of the best light for display purposes and fairly long life to the bulbs. I have these all thru my house and have got many fixtures that have had the same bulbs burning for over 8 years. The best thing is to not have fixtures that encapsulate the heat. That's what burns out bulbs. also, use the very narrow beam spread bulbs and illuminate from as far away as is possible since they have very high lumen output but in a very small beam.
Tenn. Tom , illuminating engineer in a former life.

[Michael Mortara]

We have looked but never found one that did the job, LED's have a very low lumen output. Your best bet is flouresent floods.

[Tom Fuhrman]

There are new LEDs with higher wattages, i.e. 3 watt, and also spot bulbs using as many as 24 leds for the light source. I'm involved with some lighting companies that are even making prototypes of leds used for factory lighting and possibly street lighting. Technology in this field is moving very fast. I saw many fixtures using leds at the Lightfair show last year that were mind boggling. Some with hundred of leds amassed together. Try to get ones with the very narrow beam spread. I think the newest are still overly priced for what they deliver, but will come down in price drastically in a year or 2, just as the compact fluorescents have done.

[Brian Wong Shui]

Check these out.

Quite Expensive but color corrected with a feedback loop to maintain constant color output.

LLF Inc. (http://www.llfinc.com/index.aspx)

You can also check out

LED Workplace (http://www.ledworkplace.org)

For state of the art LED devices (if you are designing your own)

Lumileds (http://www.lumileds.com/)

If you do design your own, you are going to need secondary optics to cope with the "spottiness" of the led. You are going to need at minimum a collimator and a diffuser. Also there are thermal issues to manage because a 5 watt junction gets really hot so you are going to need some sort of heat sink. Typically the LED's are mounted to a aluminum core printed circuit board which is thermally bonded to a heat sink.