Luxeon Rebel LEDs

[JamesJackson]

Recently, a salesman dropped off a few of these for us to evaluate. I spent some time wiring up a constant current LED driver, and decided to check it out today, hooked up to one of these Luxeon Rebels.

For those who may not be aware of them, they are very small surface mount LEDs that will work at several currents... 350mA, 700mA or 1A. The light gets increasingly bright, too. I believe at 350mA, they are about 100 lumens.

Well, I soldered the LED to a heatsink, crossed my fingers, and powered it up.

First impressions... it's bright! Blindingly bright!

I have not measured the light output with a lightmeter, yet - but I can tell you that there is a lot of intense white light coming from a very small die.

I have had it lit - at 750mA - for about an hour or more - and it is still working. The heatsink that I mounted it on, seems to be keeping it cool enough. It is warm to the touch - not too hot. That's a good thing, too.

I am going to try to finalize the constant current circuitry - and have pc boards made - to make it easier to mount parts on.

I figure 3 of these rebels - at 700mA - should be a good light for testing - and using - for a while.

Regards,

James Jackson

[richhagen]

I have been experimenting with their main rival, the 80 lumen per Watt LED's from Cree.  I have a few of the older lumileds, but they are less efficient.  So far I am impressed with this latest generation of LED's.  I think manufactureres will adopt them in short order for a variety of uses.  Like you, I have not measured the light output, in my case I do not have the equipment, but I have measured their consumption and compared them against other sources.





An mr-16 version drawing 2.97 Watts per my meter.  The older led light to the right is drawing just under 5 Watts and is much dimmer.  

[JamesJackson]

Thanks for your input. Nice photo.

I ran the LED at various currents, and here is what I was measuring...

At 350mA - 2.4V

.. 700mA - 3.2V

.. 750mA - 3.3V

.. 1.0A  - 4.0V

One thing that I also discovered. It helps to wear a pair of BlueBlocker sunshades when working around these bright LEDs. The shades help mute the bright light, and your eyes will thank you later.

Regards,

James Jackson

Oztronics

[DamonHD]

Are these 'cool' white (blue LED + yellow phosphor)?  I have to say that I'm not over keen on that colour if so!

Roll on efficient warm white for evening working I say!

Rgds

Damon

[JamesJackson]

Damon,

These are the 6500k LEDs. (LXML-PWC1-0100)

I like these, as they are 'whiter' in color. They are supposed to be approximately the same color as the sun at noon - if I understand color temps correctly.

At any rate - I prefer the 'whiter' over the 'oranger' colored lighting - even in fluorescents - as it is less harsh on my eyes. I find that the more orange hued lighting - personally - causes me to have eye fatigue.

Regards,

James Jackson

Oztronics

[DamonHD]

I think it does have to be a personal preference.

I'm working by the light of a (solar PV 12V) "warm white" CFL now, and found the "daylight" alternatives that I have tried in various arrangements (CFL and LED) made me feel as if working down a well and quite claustrophobic!  (My g/f is not at all keen on the "daylight" LED lamp (Cree I believe) 5x1W that I have experimentally put in our kitchen alongside some warmer CFLs, for example.)

There is recent research suggesting that it is healthier to work in the evening by a 'redder' light since a 'bluer' light forces your brain to put back its clock too much, but who knows what the actual LED/CFL spectra trigger?  B^>

Rgds

Damon

[JamesJackson]

Damon,

I guess the bottom line is that it IS preference.

One thing that I want to make clear is that the LEDs that I am using are 'white'. Not 'blue'. I know what the blue ones look like, as I built a flashlight using a 'blue-white' LED from Lamina Ceramics. It's a great flashlight, but the blueish hue is a bit... well, I am not fond of it.

The newer LEDs like I am using to light my living room are 'white'. It's a real odd appearance - you are able to read clearly - and do things in the 'white' light. Very different from CFL 'white', too, as it is a more 'pure' white light than CFLs.

Regards,

James Jackson

Oztronics

[DamonHD]

Do you have a diagram of the spectrum and/or the LED construction.

If they are not using the standard-ish blue+yellow construction it would be interesting to know.  Certainly I might want to buy a couple of samples...

Rgds

Damon

[JamesJackson]

Damon,

I did a bit of research on this. I would recommend going to Luxeon's web site and getting their datasheet on the Rebel LED.

It appears that nowadays, they are going towards the CIE 1931 color chart to describe the colors better - which is understandable when you get into 'white' colors.

http://www.biyee.net/v/cie_diagrams/index.htm

For example, the LEDs that I have are described as 'cool white' and range from 4500 - 10,000K (mine is around 5300K).

On the 'pie' color chart, .33 X and .36 Y are very near the 'white' line that runs up the right side.

The color temp that you describe is called 'warm-white' (2670 - 3500K), and its' color coordinate temps are .43 X and .41 Y - which puts the color over in the orange/yellow/red section of the 'pie'.

This also gets into the area that they are leaning towards - and that is 'color mixing'. Cypress's PSOC has the ability to do this, and - if I recall correctly - using an RGB LED array - one is able to select the color one wants - based on this 'pie' color chart. (We had this demoed for us one afternoon. It's pretty cool!)

I'm kinda new at this, and am still learning - but that's how I see it. You may see it as something different.

Regards,

James Jackson

Oztronics