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Old 18th April 2011, 12:08 AM   #21
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Here's a relevant tidbit I found today:
"In a nutshell, a 100W incandescent bulb produces around 12% heat, 83% infrared, and just 5% visible light. By way of camparison, a typical LED could produce 15% visible and 85% heat." (source: LEDs Magazine)
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Old 18th April 2011, 12:29 AM   #22
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If you're interested in LEDs you could do worse than look at candlepowerforums.com, and if you want to buy Cree or Seoul Semicon LEDs look on dealextreme.com.

w
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Old 18th April 2011, 12:53 AM   #23
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For home lighting, I'm not interested. The info in my post above says that a 60W ICL will put out more light and less heat than a 10W LED. In San Antonio, I only need extra heat about 10 days out of the year.
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Old 18th April 2011, 01:42 AM   #24
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Quote:
Originally Posted by sofaspud View Post
Here's a relevant tidbit I found today:
"In a nutshell, a 100W incandescent bulb produces around 12% heat, 83% infrared, and just 5% visible light. By way of camparison, a typical LED could produce 15% visible and 85% heat." (source: LEDs Magazine)
Indeed, I was going to say, from my experience high power LEDs are ~20% efficient. You might have 15 watts of power going into your LEDS but only 3 watts of this is actual light, the other 12 you have to provide heat sinking for.

The heat issue with LEDs really only comes into it when you're trying to design a replacement bulb for a standard fitting. If however the lamp is designed from the start as an LED light, then the heat sinking can be easily incorporated into the design (This is of course if we're talking about a standard decorative consumer lamp).

The LED array that digits posted about I've had my eye on. This thing driven at 1 amp would need about a 2 degree/watt heat sink to work within the specified temperature range. At 1 amp the thing draws about 45 watts and used at a CCT that looks nice, will produce around 2500 lumen. For comparison a normal 60 watt incandescent is around 800 lumen, so the LED is roughly 4 times as bright while using 5.3 times less power then the 4 incandescents combined.

LED lighting really isn't at the point where people think it's at. Compared to the best fluorescent and CFLs LEDs are roughly about the same in terms of efficiency. Trouble plagues cheap CFLs, but these same troubles plague cheap LEDs too. Typically, poor quality driver circuits, with crap power factor correction leading to significant power being wasted before it's even reached the bulb. Then the bulbs don't last anywhere near their specified lifespan.

Where a good LED bulb wins vs a good CFL is in the lifespan, but also in the clean up, they are far less of a hazard to the environment. The problem is the price though, LEDs ain't cheap! Ironically, of the good quality LEDs available, Cree happen to make some of the best and some of the most affordable too.
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Old 18th April 2011, 01:45 AM   #25
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Digikey has a ton of info on this subject in their TechZone area

Lighting Solutions | DigiKey Technology Zone
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Old 18th April 2011, 01:55 AM   #26
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Quote:
Originally Posted by sofaspud View Post
For home lighting, I'm not interested. The info in my post above says that a 60W ICL will put out more light and less heat than a 10W LED. In San Antonio, I only need extra heat about 10 days out of the year.
All the energy ends up as heat. In both cases.

LEDs are currently ~as efficient as sodium street lighting, which is as good as you can get in efficiency terms, the quality of light is better, and they are increasingly being adopted for street lighting. They will get better in future. They offer the possibility of near complete conversion of power to light (in the first instance), which means a cold luminaire.

The other advantage is that their lifetime is considerably longer than any other lighting device.

And anyway, I didn't offer the information solely for your benefit.

w
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Old 18th April 2011, 02:23 AM   #27
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My information was directly related to the question posed in the thread title. It wasn't about thermodynamics quibbling or future prospects.
Take a hit and chill, bro.
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Old 18th April 2011, 02:30 AM   #28
18Hurts is offline 18Hurts  United States
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I've been playing around with high power (1+ watt LEDs since 2002

They make great bike lights and don't blow out like hot wires. From what I gather, the max output--the 100% efficient blue/phospher LED will put out 330 lumens at one watt. My Cree XP-G bin code R5 LED puts out around 140 lumens at one watt but I run it at 2.2 watts for 285 lumens. At the higher drive rate the efficiency goes down (just like a speaker) I'm sitting at around 130 lumens per watt. Not bad, around 40% efficient and 60% heat.

Cree has a LED in their lab that puts out 210 lumens at one watt or 64% efficient--four of those at 4 watts will put out the same amount of light as a 60 watt incandescent bulb but only 1.5 watts of heat. Granted, the "bulb" has to run on DC so you'll lose power through the AC to DC conversion but even at 5 watts--much better than 60 watts!

Technology is getting there, back in 2002 my Luxeon I was pumping 17 lumens per watt and I was amazed! Eventually, your walls will be OLED wallpaper for video displays and room lighting. Adjust the output and tint to your liking then use the other wall for Horn Response.
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Old 18th April 2011, 05:55 PM   #29
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To anyone interested: as far as the LEDs meant for home use, do they exhibit any visible flickering like those LED-based Xmas light strings or the ones used in many automotive tailamps? I hope not.

That's one thing about incandescents I definitely like, and that's their pleasant and "relaxed" light they emit. An example on a much larger scale was on display 2 years ago at a local - and old, about 60 years IIRC - high school gym where I attended a sporting event. I wasn't specifically looking for this effect and we were seated a couple minutes when I realized something was different about this room. Everything was perfectly visible but looked, well, relaxing. Looking up, I realized that the light was being provided by enormous incandescent bulbs, the kind I haven't seen since I was in elementary school in the early 70s (Google tells me these were probably in the "PS35" bulb category). Just a very nice experience, especially compared to the nasty & "sharp" effect that typical modern gym lighting produces.
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Old 18th April 2011, 06:19 PM   #30
tomchr is offline tomchr  United States
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Quote:
Originally Posted by River757 View Post
To anyone interested: as far as the LEDs meant for home use, do they exhibit any visible flickering like those LED-based Xmas light strings or the ones used in many automotive tailamps? I hope not.
Depends. Incandescent bulbs have the advantage of the thermal mass of the filament smoothing out the AC and produce a light with minimal flicker. LEDs and CFL's are much faster devices. Some el-cheapo Christmas light strings run half-wave rectified, hence, are off for half the AC cycle. Many people are bothered by the flickering of those. The better light strings run full-wave rectifiers. They still flicker, but they do so at 120 Hz and are only off a tiny fraction of the AC cycle, hence, the flickering is very hard to notice. Of course, all you'd need to eliminate the flicker would be a small cap on the output of the rectifier...

As for LED bulbs, the ones I've tried haven't flickered. In the "old" days with CRT monitors, I would be bothered by 60 Hz refresh flicker so I think I'd notice if an LED was flickering at that frequency. As far as I understand it, the LED driver ICs are essentially switchmode supplies that pulse width modulate the LEDs at some frequency well above the audio range. You shouldn't notice any flicker with those.

My only complaint about LED lighting is the color temperature. The warm glow of an incandescent bulb is nice. But a quality LED bulb should get pretty close to that...

Times change. I'm sure a lot of people were missing the pleasant warm glow of carbon filament bulbs when they went out of fashion and were replaced by the more efficient tungsten filament bulbs.

~Tom
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