Top performing LEDs
Posted by Matthew
The popularity of my previous article reminded me of some new record setting LEDs.
In the increasingly popular world of light-emitting diodes (LEDs), an emitter’s light output per given input (efficiency), heat management, and small footprint are critical. So if you can make dramatic advancements in just one of these three areas, you’ve done a lot.
LED performance is quantified by the input power (Watts) required and the output intensity (lumen). A lumen measures the luminous flux (light energy passing) through a particular surface. It accounts for light emitted in all directions. The new Luxeon K2 LED breaks all these barriers.
A white light output at a color temperature of 6500 K with 1500 mA of drive current and a forward voltage of 3.85 V produces 140 lm.
This corresponds to 4 W of input power and 35 lumen per Watt. Comparatively, a standard incandescent bulb emits around 855 lumen at 60 Watts or 14 lumen per Watt. Current LEDs perform at about 20 lumen per Watt. Most professionals don’t expect LEDs to be used for mainstream lighting until they reach about 100 lumen per Watt.
Matthew, am I reading the the Luxeon documentation correctly when I see the 350 milliamp version of the K2 white bulb producing 50 lumens per watt? 3.42 volts x 350 milliamps is 1.197 watts per emitter and each 350 milliamp emitter produces 60 lumens. 60/1.197 is roughly 50 lumens per watt.
However, I’m a software guy and I don’t know my amps from a hole in the ground. But if I do have it right, I may buy a few of these. I’ve been planning to build a lamp for my living room and I’d love to have a cool, dimmable, energy efficient solution.
Great blog, BTW. Very informative.
Yes, you are reading correctly. 50 lumens per Watt! You might be able to find something more cost effective, though. These guys are pretty pricey! (Of course they are also the coolest and most efficient)
One important thing to remember with LED lighting. High performance LEDs perform unreliably and inefficiently unless you provide the rated current and voltage. If you plan on dimming the LEDs, be sure to use pulse width modulation (PWM) instead of continuously reducing the voltage.
Also, check out Myths Busted, LED Lighting. A great article by Pat Mullins who conducts research in the area of outdoor LED lighting.
I have no direct experiencing building LED lighting, but I would not rely too heavily on lumens for calculating how many LEDs you will need in your array. Specific LEDs, fields of view, and environments can change these figures dramatically.
Thanks for the tips Matthew. Given the cost of the components and my lack of experience I think it might be worthwhile to build a lower power prototype using cheaper LEDs until I’m sure I’ve got it down. I’ll head to Fry’s tomorrow and see what I can find. Should be fun!
Does Fry’s sell LEDs, passive components, and IC chips? I’m in the northeast and there are no Fry’s near here.
The good thing about LEDs is that you can buy cheap ‘ultrabrights’ to see how everything works. Only the high-end LEDs are expensive.
You also inspired my latest post you may or may not know everything in there, but it is worth a read and possibly a digg.
I think I can effectively design a light bulb around a led for street lighting in signs.
Hi Matthew, I’ve been reading about the K2 for a DIY aquarium lighting experiment. They do seem amazing compared to the 65 lumen 3 watt leds. It would be made up of blue and white leds and each would have to be dimmable to emulate night and day and moonphases. What would be the best way to design a controller for all this daily dimming. X10? Also there would be many leds in a cluster. You seem like a GURU in this subject. How would you design such a system. I’m not gonna lie, I have hardly any electrical experience. Just worked with LED’s while building PC’s. Thanks for any help.
Forgot to mention that the first LED lighting system for aquaria has just been released by PFO lighting. It uses 3 watt LED’s and people are reporting good results. PAR numbers have been higher that a 250W 20K Metal Halide Fixture. Here is a link to PFO’s LED solution. Very expensive. http://www.solarisled.com/
I’m a little late finding this article, but I loved it.
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