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Sulaiman

Sat Mar 28 2009, 03:10PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Would it be possible to show a normal filament lamp at similar power for reference?
I can't think in kCandlePower !

Looks promising ...

Is each cell a blue led with a phosphor like the 5mm eBay China ones?
or is it something else?

Dr. Dark Current

Sat Mar 28 2009, 03:21PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Sulaiman wrote ...

Is each cell a blue led with a phosphor like the 5mm eBay China ones?
or is it something else?

You can only get white light from LEDs by using phospors (99% of white LEDs) or by using RGB LEDs. So I'm pretty sure this one uses blue LEDs with phospors.

Electroholic

Sat Mar 28 2009, 04:26PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

yes, the yellow stuff is the phosphor, but these chips are a lot bigger than the ones in normal 5mm leds, these are more like chips you would find in a 3W luxeon or something.

Tesladownunder

Sat Mar 28 2009, 05:29PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

This is a 100W LEd made from a 100 x 1W LED's. Output is 7000 lumens.
Since 1W = 683 Lumens for 100% efficiency then this LED is about 10% efficient. ie produces 90W of heat.
Typically 34V at 3.2 A. Obtained from eBay store here.

This is a pic of my shed lit with one plus a 150W incandescent globe for comparison.

Dr. Dark Current

Sat Mar 28 2009, 05:55PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Talk about stupidly bright

The luminous efficacy is 70lm/W but this does not say anything about how much power it converts to light. This is because luminous efficacy is weighted according to the photopic sensitivity of the eye, which is the highest at green light and falls to the blues and reds.

Even if the LED did radiate ALL of its power in the reds, its luminous efficacy would NOT be 683lm/W. (at least thats how I understand it).

So the power-to-visible-light (400-700nm) conversion efficiency of your LED is probably quite higher, so it radiates less heat. Also some of the spectrum might be radiated in the near-infrared, which I don't know if can be classified as "heat".

tesla500

Sat Mar 28 2009, 06:43PM

Registered Member #347 Joined: Sat Mar 25 2006, 08:26AM
Location: Vancouver, Canada
Posts: 106

For white light, approximately 250lm/W is 100% efficiency, but that may change depending on the spectral content of the light. So your LED may be about 28% efficient. Still nowhere near that of the light source it replaces, high pressure sodium lamps are about ~100-160lm/W depending on wattage, higher wattage being more efficient.

I also read somewhere that low pressure sodium lamps are up to 80% efficient, but they're not used much because they produce one wavelength of orange light only, and nothing else. As an example of their efficiency, they need to be run inside an evacuated glass "thermos" to keep them warm enough during operation.

David

Steve Conner

Sat Mar 28 2009, 07:06PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Nice LED, Peter! Looks like it sparked the old debate on how efficient white LEDs really are.

For a start, they are handicapped by having to be white. This wastes power in wavelengths that the eye isn't particularly sensitive to.

One important reason why those low-pressure sodium lamps are so efficient (or efficaceous, rather) is that they emit all their power at one wavelength near the peak sensitivity of the eye. So they score highly on lumens/watt, the downside being that everything looks either yellow or black.

We used them extensively for streetlighting over here, up until a few years ago when the city council mysteriously changed to HPS and metal halide. I have one of the old 90W LPS streetlamp tops that I found by the roadside, and yes, the bulb has a kind of thermos-like outer, and switching it on in the living room is pretty unpleasant.

Tesladownunder

Sun Mar 29 2009, 01:22AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I was falling asleep last night when I did the last post so didn't include the info about luminous efficacy or some of the pros and cons re street lighting. Many US cities including LA and NY are doing feasability studies on replacing their 100,000 plus streetlights. Low pressure sodium is unpleasant because of the monochromatic yellow but very efficient. High pressure sodium is more white but less efficient. LED's are about as efficient but have lower maintainence. There are other advantages in smaller packaging and better beam direction to reduce wastage. For example there are different beams for a street than an intersection or junction. All this does stack the data in favour of the LED. Cost being the main difference.
A range of streetlights is here up to arrays of 200W.
I did get to use it at Earth Hour and briefly turn most of the other lights off.
I built it up into PVC tubing with a rectangular connection that just nicely fitted the heatsink/fan. I was making the shaft to accomodate 3 SLA 12 batteries. Then I thought it might look interesting as a mechanical arm attachment vaguely reminiscent of Iron man or one of the Transformers (robots).

Avi

Sun Mar 29 2009, 02:05PM

Registered Member #580 Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410

LED healing (sarcastic, like sci fi films)

aonomus

Sun Mar 29 2009, 05:13PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Is it time for the obligatory 'I'm charging my laser'?

Regardless, for $300US, was it really worth it for 100W? At $3/W, I suppose its par for the course for 1W luxeon stars, (although 3W's seem to be a little better for $/W ratio). Not too sure about the newer Rebel stars, etc, but for the convenience of the package, I suppose it was worth it...

Mount it to a bicycle and blind motorists...

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