Luxeon's at 3v

Mutie

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Dec 12, 2002
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Luxeon\'s at 3v

I bought my first Luxeons two months ago. These are blue LS/O, direct drive off 2 AA, no heat sink, mounted on the palms of my LED fingers. I'm quite happy with the results.

However with everything I've read on here I feel like I'm wearing a headlight at the mall. Before I got them I read the spec sheets and the thermal design specs and I was really worried about the heat issue. But it was all theoretical and I had to see for myself so I got 2. My neighbor does all the repair and maintenance for Warner Bros Recording and has all the right equip and was also curious so we ran our tests on his equipment. We ran from minimum to maximum specs using a current regulated supply at 350 ma. There was not really any noticeable difference in either brightness and the warmest the LED got was lukewarm. I notice everybody here overdrives and/or uses dc to dc converters even though 3v seems to be quite within specs. So what am I missing and how much brighter output are you getting to make it worth all the extra hassle? I also clocked 12 hours of run time with great brightness before I forgot to turn them off and killed the batteries. That also seems to go against what I'm reading here.

Also having read about the Royal Blue 5 watts on here I'm anxious to get and try some. Same fears and questions really that I had with the 1 watt. Also specs seem to indicate that 6v is within specs but somewhere on here I read 6.8v to even fire. How hot do these really get when driven within specs? With my design constraints I really don't want to go with converters or heatsinks unless I have to. Obviously if I have to then I'll adjust my designs but I'm really hoping that like the 1 watt it will work.
 

EMPOWERTORCH

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May 1, 2002
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Re: Luxeon\'s at 3v

I think that you could safely drive the LED in a 3 cell. My Luxeon converted 4D mag torch runs on 5 C cells. The Luxeon installed is 5W. cyan. Since I didn't mod this torch, I don't know whether waynej used a resistor or not.
 

highlandsun

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Aug 11, 2002
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Re: Luxeon\'s at 3v

With alkalines the internal resistance will keep you in the safe zone. I hooked up a white LS to 3 1.2V NiMH AAs and measured 900mA at 3.45V. I only let it run for a couple seconds, after shutting it off I could see a little bubble in the yellow phosphor coating; I think it was melting/flowing/redistributing itself.

If you're only using two cells you should have no problems either way.
 

Jonathan

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Dec 14, 2001
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Portland, OR
Re: Luxeon\'s at 3v

Originally posted by Mutiny Sfears:
Also specs seem to indicate that 6v is within specs but somewhere on here I read 6.8v to even fire. How hot do these really get when driven within specs? With my design constraints I really don't want to go with converters or heatsinks unless I have to. Obviously if I have to then I'll adjust my designs but I'm really hoping that like the 1 watt it will work.
<font size="2" face="Verdana, Arial">I believe that you are reading the specs incorrectly.

If you feed 3V (for the 1W devices) or 6V (for the 5W devices) to a Luxeon it will not necessarily be driven correctly. Depending upon the particular device in question is might be overdriven or it might be underdriven.

Basically the Luxeons are specified to be driven at a particular _current_ level. The datasheet specifies a range of voltage levels which may be required to get the specified current to flow. For example, a white 1W emitter might require anything from 2.79V to 3.99V in order to be driven properly, and the exact voltage required will be different from device to device. If you happen to have a device which requires 3.8V and you feed it 3V, it will be quite dim.

Now, the Luxeons will be efficient and will produce light at less than their rated current, which means that if you give a Luxeon less than its 'spec voltage' it will still function and produce light...just less light than at full specified current. Additionally, member experience here suggests that the 1W Luxeons can be driven at considerably more current than the spec 350mA.

Good luck with your experimentation!

-Jon
 
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