low power eff: 5mm or luxeon

which are better for 5mA or so?

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AilSnail said:
which are better for 5mA or so?

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I believe that it will vary with the particular samples compared. I suspect that statistically the Luxeons would do better on average, especially if compared on the basis of power efficiency rather than current efficiency.

cool, many thanks /ubbthreads/images/graemlins/grin.gif

Yea I guess luxeons have lower Vf generally, at that power level. then I guess I'm back to the low power: 1w/3w efficiency question /ubbthreads/images/graemlins/tongue.gif - any data on that?

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AilSnail said:
cool, many thanks /ubbthreads/images/graemlins/grin.gif

Yea I guess luxeons have lower Vf generally, at that power level. then I guess I'm back to the low power: 1w/3w efficiency question /ubbthreads/images/graemlins/tongue.gif - any data on that?

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The only low current data I have for a 1W/Lux III comparison is for 6 Q bin 1W and 4 S bin Lux III. Test current was 92 mA. The outputs of the 1Ws overlapped with those of the Lux IIIs but the average of the 1W group was lower than the Lux III group by about 10%.

5ma? If I remember right...the original Infinity runs the led at 20ma...after the step sucks up it`s part. I may be wrong, but I would question if a LS would even glow at 5ma. My guess is the 5mm or even a 3mm might be brighter at such a low level.

Ken

Running a White 5mm, and A luxeon in series at 20ma
They both light up, but the 5mm Part is much brighter

I was going ot say under 20mA I would think the 5mm would be brighter. I have a 5mm running at about 5mA off 3 D cells in the baby's room, it lasts forever and is more then enough to see by at night, and no cords /ubbthreads/images/graemlins/wink.gif The batteries are hidden bedind a little stuffed bear.

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INRETECH said:
Running a White 5mm, and A luxeon in series at 20ma
They both light up, but the 5mm Part is much brighter

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Brightness is not actually a recognized photometric unit but it appears that many people use it casually to mean luminous intensity [think candlepower]. A typical 20 degree 5mm part will certainly have a higher on-axis intensity than a luxeon. Total radiated flux is another matter. It is very hard to make accurate eyeball comparisons of total flux of two sources with radically different distribution patterns such as a luxeon vs a 20 degree 5mm part.

Tis true, but I would still be willing to bet a Luxeon at 5mA and a 5mm at 5mA, the 5mm would produce more lumens. Also doesn't the Luxeon require a higher voltage, meaning if they were both driven at 5mA the Luxeon would require more overall power?

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Brock said:
Also doesn't the Luxeon require a higher voltage, meaning if they were both driven at 5mA the Luxeon would require more overall power?

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No, definitely not.

I stand corrected.

Thanks

To me the Luxeon definately put out more photons than a 5mm Nichia even at low levels. A Luxeon driving at 20mA typically has lower Vf than a 5mm driving at the same level. Because a Luxeon die is 10+ times bigger than a 5mm Nichia die, you are looking at much lower current density, which gives you lower Vf, lower die temperature and higher efficiency. IMO the problem of using a good Luxeon at such a low level is more associated with the cost/performance ratio.

[edit: took too long to reply /ubbthreads/images/graemlins/tongue.gif ]

In relation to the Vf question:

The luxeon typically has a lower Vf relative to its rated current.

at 5mA, I would guess a luxeon would have a Vf of around 2.7V. Looking at the Nichia data sheets, 5mm have a Vf of about 3.2V at 5mA.

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Brock said:
Also doesn't the Luxeon require a higher voltage, meaning if they were both driven at 5mA the Luxeon would require more overall power?

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At 5mA my Q2H's only need about 2.7V. A Luxeon MOST certainly WILL light up with only 5mA. That's about the level I have as the nightlight setting of my uFlex driver.

At 5mA you get quite a decent amount of light out of a Luxeon and as Doug S mentioned - it is a WIDER beam than a 5mm LED.

I'd put my money on a Luxeon putting out more photons at 5mA and doing it more efficiently.

george.

I saw a paper by a young college student who used an array of 100 luxeons and 100 5mm Nichias, all at a low current (5-10mA), and as I recall, he got nearly 2X the light out of the Luxeons.