LEDs are mature

I have a couple of street-light grade LEDs. At 12 volts/1 amp, they look like welding arcs. Blinding.

If you need a tiny spot of light, they are blinding. But, for area lighting, pulling the round number 100 lumens/watt out of my ass, you've got 1200 lumens. 100W incandescent can do better than that.

If you need a tiny spot of light, they are blinding. But, for area lighting, pulling the round number 100 lumens/watt out of my ass, you've got 1200 lumens. 100W incandescent can do better than that.

Most modern high power LEDs can now easily achieve 125-140Lm/W. The mid power chips we use are rapidly approaching 200Lm/W! Incandescent is still well

Some of them the active LED die is now approaching the luminosity of the solar photosphere when running flat out on a decent heatsink. It tends to degrade the phosphor and darken the plastic at that intensity.

You must live on a different planet then! The melting point of tungsten limits incandescent lamps to typically no more than 20Lm/W round here (and 15 is a good working number).

A few projection bulbs do better Lm/W with forced air ventilation and short working lifetimes but incandescents are much less efficient.

LED efficacy at converting electricity into light is fast catching up the ultimate monochromatic low pressure sodium lamp in terms of Lm/W.

It is not completely fair to compare 100W to hot wire and 12W to LED.

I think the point was that a 'street-light grade LED' at 12W would give about 1200 lumens, which is comparable to a 100W incandescent, and might seem a bit low for street lighting.

The lamps I took from street lights as a kid were 150W, so in fact 1200 lumens of LED would be in the right ball park, particularly with the better control over the lit area.

Cheers

It's also not a tiny spot of light. It's more like a car headlamp, if not brighter.

Running a LED well below rated current, it is possible to achieve

For such life expectance, the LED needs to be run below 1/3 of the rated current. In fact, the life expectance of the control electronics (especially electrolytic capacitors) may be the limiting factor.

Currently discharge lamps have to be relamped every few years due to light output degration. Avoiding this would compensate the cost for larger number of LEDs in the fixture.

Sounds like it's finally possible to use them as a strobe, though a flash tube is still probably cheaper.

The claims from reputable LED manufacturers (eg. Philips) are more like 2-3x the life of the most popular discharge technology (Sodium)-

Minimum duration of flash for a given total light output may be disappointing if you don't grossly exceed the specs.

We've used them for human vision strobes.. 10-100 ms on times (not sure of the exact number.) But not for stop action photography.

George H.

Yup. Overcurrent causes migration of defects and interstitial atoms--you can see it in the 1/f noise. The die basically disassembles itself. High temperature aggravates that.

Cheers

Phil Hobbs

My billboard LED drivers (25mA) are spec'd at 25ns max TR/TF. I don't know about light output, but I've had a recent inquiry to quote using my (patent-pending :-) scheme for cellphone camera flash. ...Jim Thompson

Not my design, but the issue was not on/off speed (in this application) but getting enough photons into the eye. (used to measure the angular frequency of a pool ball rotating in a spherical air bearing.) In room lights.

George H.

You're missing my point. It's not about efficiency. I merely used some random efficiency numbers as a back door approach to guesstimate how much light might be coming out of the LED. I compared that to a 100W incandescent and suggested that the LED in question ain't "blinding" when used as area lighting.

I got a nice LED flashlight for Christmas. I looked at the LED, thought "oh how cute", and turned the thing on. OW!

So, now I have it internalized that LED's are _different_ in the 21st century.

outside. With the beam on its highest regular setting coming from eye level, I could see what looked like moderate to heavy snow with the "snowflakes" probably being teeny tiny little specks of pollen.