Overdriving a LS

[NightShift]

Can you overdrive an LS safely if its attached to a heatsink. I have one attached to a heatsink and running at about 870mA 3.4v

? and the heatsink gets hot...too hot to keep your fingers on it after about 5 minutes at a steady temperature of 135 F.

 

[KenBar]

Like living on the edge..

!!

I have mine attached to a HIGH quality heat sink,LOTS of heat sink compound, firm mechanical connection while only running at at 300ma and 3.2 volts.

 

[Quickbeam]

I'm finding the same thing.... These things tend to get too hot to run on more than 3V in a flashlight unless you have really good heatsinking and ventilation or you can regulate the current rather than the voltage. Check the specs for the temp where they toast - I don't remember the numbers but it's quick to get there even if it isn't "overdriven" unless precautions are taken.

 

[snakebite]

anyone mount one on a peltier cooler?
but you could buy a whole bunch of smoke bombs for the cost of one ls

 

[NightShift]

So what do you think about 800+mA....will that kill it in no time?

 

[NightShift]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by videocal:
I don't know, but are you going to keep that setup running for awhile?<HR></BLOCKQUOTE>

Well, I only jumped it directly to the batteries for 5 minutes to see how hot the heat sink got (while crossing my fingers). Right now its running off of the resistor unitl i could figure out if it was safe or stupid.

 

[vcal]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by NightShift:
Well, I only jumped it directly to the batteries for 5 minutes to see how hot the heat sink got (while crossing my fingers). Right now its running off of the resistor unitl i could figure out if it was safe or stupid.

<HR></BLOCKQUOTE>

OK.....
But can you tell if the resistor is getting hot?

 

[NightShift]

The resistor never gets hot....or even warm...

 

[JoeyL]

The luxeon website says the maximum current should be 350 ma, with a peak pulse of 500 ma. They dont say what will happen at higher levels, but that the maximum temperature at the aluminum core should not exceed 105 C.

The 350 ma might be a rating without the heat sink, so the heat sink could allow it to take more current, but I'd wager it wont last too long at 800 ma. (at least not 50,000 hours!)

You should look at the data sheets at www.luxeon.com. What I don't understand is that the only graph they give of light output has its relation to temperature, not of voltage nor amount of current flow through it. It shows that light output decreases with temperature. But increasing the current distinctly makes it give off more light, and hotter as well. Do you guys understand this?

 

[vcal]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by NightShift:
So what do you think about 800+mA....will that kill it in no time?<HR></BLOCKQUOTE>

I don't know, but are you going to keep that setup running for awhile, -for the sake of science?

Inquiring minds want to know..

 

[The_LED_Museum]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by JoeyL:

The 350 ma might be a rating without the heat sink, so the heat sink could allow it to take more current, but I'd wager it wont last too long at 800 ma. (at least not 50,000 hours!)<HR></BLOCKQUOTE>

The 350mA figure assumes the device is installed & driven with adequate secondary heatsinking - not just the bare MCPCB the lamp is mounted on.

At 800mA, your $18 investment will end up on the bottom of the toilet bowl very soon - anywhere between 90 seconds to several tens of hours - depending on how lucky you are.

Damaged units may appear bluer than they did before, may have a higher threshold current, and/or not produce as much light for a given drive current than an undamaged unit.

Place your abused unit and a new one side-by-side, and feed 100mA into both, and see which one is brighter.

Chances are, the new one will beat out your 800mA power warrior by a visible margin in this test.

 

[JoeyL]

Stingmon,
Thanks for the clarification.
I just did another timed test with a new duracell 123 and white LS
Initial draw with battery voltage at 3.18v
was 320 ma.
at one hour, voltage 2.98v and 167ma.
at two hours, voltage 2.80v and 160ma.
at three hours, I stopped volt checking and
was 160 ma.

At this point, it was brighter than a nichia white with 70 ma.
In the first hour, the brightness was very close to the E1's native 15 lumen bulb with a new battery, but better than an E1 with a battery about 1 hour old. (rated for 75 min).

This makes putting this luxeon into an E1 pretty attractive, except the bezel looks pretty hard to dismantle or drill through.
hmmm...