Some questions for the LED savvy members

Yes.

Sure.

The control circuitry is practically free.

Of course, the LEDs will come in at around $100/$160 per bulb equivalent. And will probably need a fan, or heatsink per.

You may need a bunch of them. But they could change colors as well as just brightness. Using RGB LEDs, you could get a large number of effects. Or just white. The color temperature of white LEDs tends to be higher than that of even halogen incandescents.

Sure.

Maybe less, they'd need a low voltage supply (like a LV Halogen) and some control circuitry. Depends on what this "random" thing is all about, but it's not difficult to get that kind of effect with LEDs.

Just for fun, I whipped up a green and white LED "spooky light" for inside a ghostly-white pumpkin just before Halloween. It would be similar, but on a larger scale. I just used a microprocessor (running a little program I wrote) and some transistors to drive the (about) half a dozen super-bright 5mm LEDs I used.

Best regards, Spehro Pefhany

Luxeons are the brightest LED's by far. They're about twice as efficient as indandescants, so a 3-watt Luxeon would be equivalent to about 5 or 6 watts of incandescant light -- if it's white light. If it's colored light (red, green, blue, etc) then the Luxeons are more effective: a 1-watt red lux is about equivalent to the 12-watt 1157 brakelight on a Chevy truck. A 3-watt red Luxeon probably would be comparable to a color-filtered 25-watt incandescant. Color filters significantly reduce the brightness of incandescants, but colored Luxeons emit all of their lumens as light of the particular color at hand -- no filter.

3-watt Luxeons are about $8.50 each. Lifetime to 50% brightness is 20,000 hours if run at 1 amp, 50,000 hours to 70% brightness if run at 0.7 amps. Yes, with electronics they are dimmable -- and they don't change color when dimmed, liked incandescants do. With multiple colors, both brightness and color could be varied. Electronics for use on mains could be very inexpensive if optimal efficiency isn't a big deal.

Depending on the situation, you may find that the light can be directed well enough with available inexpensive ($3.50) molded collimators that you don't need as many watts (lumens) as you think

-- particularly if you use colors.

There is an upscale apartment in London (Chelsea) that did some interesting illumination with Luxeons. Check out

Email me if you'd like to discuss Luxeons and/or elex to drive them further. I'm fascinated with them!

The easiest way to dim a LED in your case would be to use a light dimmer module in the wall and use that to drive a low voltage transformer that will put out only enough voltage to light the LED to full brightness at line voltage input. You need to turn the output of the transformer into DC voltage but that is easily done with a bridge rectifier and a large cap. if you desire. If you do this, lower voltages will end up making the LED dimmer.

-- Why isn't there an Ozone Hole at the NORTH Pole?

"Bob May" wrote: (clip) You need to turn the output of the transformer into DC (clip) ^^^^^^^^^^^^^ Just out of curiosity, what would happen if you applied AC? Would the light go dark on the "wrong" half cycle, or act like a short and burn out?

Thanks; Googling around the web I was coming up with similar numbers.

But, this is for a very public space here in Chicago and the array would contain 60 or 70 elements. In incandescent that would probably get listed as 60 of 70 separate electrical fixtures. Half that cost could be saved in permit costs alone.

Plus, it is gonna cost them at least a hundred bucks every time they have to get somebody on a lift to change the bulbs.

Paul K. Dickman

An interesting idea. She did not even know what an LED was when I suggested them. I think she'll stay with white at this point, just to keep her confusion down, but it would increase the possibilities for future projects.

I think she just wants to have about 50% lit at any one time, each randomly selected piece would go from off to fully lit to off over a period of 15 to 20 seconds.

Thanks Paul K. Dickman

I looked at the luxeon info. It was pretty impressive. Their flood arrays looked like they had the right jazz and their dispersion pattern looked like a good match for the shape of her objects.

I think the translucency of the glass used for the objects and the fact that the sculpture is behind a south facing window will require as many lumens as we can muster.

Very interesting stuff

I probably will.

Thanks Paul K. Dickman

An interesting concept, and one I'll keep around for my own use (maybe I'll come out of this with a pocketful of LEDs) but, as I mentioned in another post this is for a very public building in a big city, I imagine we'll have EE's from the dept of construction and permits, crawling all over this.

Thanks Paul K. DIckman

Greetings Paul, After reading the above post about permit costs it made me wonder if the permitting would be easier and/or cheaper because the LEDs use low voltage. It sure makes a difference where I live when it comes to putting lights along the driveway and similar situations. With the low voltage I don't think it even needs UL approval. The power supply, which has a high voltage input needs UL approval, but that is store bought. Everything that's connected to the output is not considered a shock hazard. Like those halogen track lights that are suspended from uninsulated wires. ERS

That's my thought. Plus wiring would be a lot simpler. No running conduit or bx, just running low voltage wires through the walls.

And the things have a low enough profile, that the fixtures themselves could be surface mounted.

As an added bonus, this is for a corporate "Green building" The energy efficiency of the LEDs could help sell it.

Paul K. Dickman

I remember from doing many trade shows in Chicago that they are really fussy about anything that could cause a fire. They've had problems in the past, as I understand it.

Best regards, Spehro Pefhany

Which reminds me of a friend of mine who got a contract to build a bunch of those signs with the flashing lights that the road works people use to warn drivers to merge lanes and such.

You know the ones. Big yellow arrows flashing in sequence...

He did them using leds and everything worked great until the sun came out.

They ended up in the dumpster, and I don't recall what my buddy said about who paid for what!

Now this is some time ago and there were no super brights at the time but...

DOC

Paul, I've been doing some research on low voltage lighting for one of my clients and "IF" I remember correctly, low voltage circuits (50v or less) have much less stringent requirements as far as conduit and fixtures than "mains" voltage. My sources are ICC and NEC. In the next couple of days I will get chapter and verse for you if you like. I am currently working on several low voltage lighting projects and the company I am working with are quoting a light output ratio of incandescent to LED of about 8 or 9 to 1 (their claim not mine). If you like, I would be happy to discuss some options with you off group. They might be interested in your project, they are currently going a huge light sculpture in a shopping center in Asia.

Mooo.

Jim

there is a device you can buy that is called "sauce" - you can buy it at some retail stores - a bunch of LEDs and a microcontroller that put out varying color light.

jim rozen wrote in news: snipped-for-privacy@drn.newsguy.com:

Nah, it (McCormick Place) burned to the ground while a housewares show was being held there.

of the worst fires in the cities history.

Dan

Thanks for that link.

Best regards, Spehro Pefhany

(snip)

That claim must be based on LEDs of various colors compared to incandescants working thru color filters. It's not true with white.

2.5 : 1 would be more in the ballpark.

A typical 25-watt halogen lamp produces about 200 lumens. Ref:

's about 8 lumens/watt. A white Luxeon III nominally produces

80 lumens at about 3.9 w (1 amp at 3.9 volts). That's about 20 lumens per watt, giving a ratio of about 2.5 : 1.

Bottom line: three white Luxeon III's would be brighter than an unfiltered 25-watt halogen incandescant light, while using less than half as much energy.