Burnt-out luxeons

Hi, guys,

As I read some time, here are some led professionals. I have a problem, and maybe you can help.

I bought months ago some LuxIII for a homemade kitchen lamp, and made some trys with different power supplies, cooling, etc.

I have some burnt-out parts, and uploaded to yahoo:

Maybe you have more experiencs with this led, i hope you can answer some questions. There are 3 leds. All is discoloured, as you see.

The luxbad2.jpg, i think got a high current, and the gold wire became coal
The luxbad1.jpg only discoloured and it doesn't lit anymore. It was serial connected to others. The LED was killed by something, and the connection broke, the full series became dark.

The Luxbad3.jpg is interesting, there is some fault in the lens material, as i signed with red. The led is dark, and the circuit is broken.

Can you help me, why these events occured? Maybe you know more about this, than me.

Thanks a lot

Whoa! Those stars are COOKED!
It looks like excessive current to the LEDs by the charcoaled gold wires to the emitter. What kind of heat sinking did you use for those LuxIII's? By looking at the heat damage, I would say you need to put much better cooling on your next try and use a regulator to limit current.
Have a pic of what the entire setup looked like so we can evaluate your cooling and drive levels?

Ya looks like heat damage.
Needed more information about circuit and cooling.

ledlamp999 said:

Hi, guys,

As I read some time, here are some led professionals. I have a problem, and maybe you can help.

I bought months ago some LuxIII for a homemade kitchen lamp, and made some trys with different power supplies, cooling, etc.

I have some burnt-out parts, and uploaded to yahoo:

Maybe you have more experiencs with this led, i hope you can answer some questions. There are 3 leds. All is discoloured, as you see.

The luxbad2.jpg, i think got a high current, and the gold wire became coal
The luxbad1.jpg only discoloured and it doesn't lit anymore. It was serial connected to others. The LED was killed by something, and the connection broke, the full series became dark.

The Luxbad3.jpg is interesting, there is some fault in the lens material, as i signed with red. The led is dark, and the circuit is broken.

Can you help me, why these events occured? Maybe you know more about this, than me.

Thanks a lot

Click to expand...

Did you hook them up directly to a 12v power supply or something? We need more info on how you tried to power these.

I am not an electrician, just asked a friend to build a circuit for 12VDC.
The cooling was poor, i screwed them on a 3 cms diameter 1.5 cm thick alu stick and screwed this mounting on the plasterboard directly. Maybe the cooling was poor. This causes the brown colour on the mirror?

Thanks

12 VDC into three series LuxeonIIIs could be OK as long as they have high forward voltages (say a ---M) Your cooling is terrible to dump over 10 watts of heat though. If you were running say TWOJ Luxeon III's, the forward voltage of those is between 3.28 and 3.50 volts or around 3.4 volts on average. Run three of those in series and you would want to run around 10.2 volts at 700mA to run them at spec. They would be at a forward voltage of around 11 volts at 1,000mA which would be at their specified limits. 12V would hammer them at around 1,400mA or higher and cook the little guys.

The only way I would run luxeons off a 12VDC power supply is by running four of them in series. Say you had TWOJ bin Luxeon III's... they would most likely run at 250mA to 350mA each in that configuration but would generate much less heat. Mount them on a large square section of aluminum bar and put a computer heat sink on the top to add fins to aid in cooling. Four luxeons running this way will cover 360 degrees no problem and should stay cool as a table lamp.

Underdriving TWOJ LuxeonIII's will also shift the color tint warmer which might be a good thing for reading. Is your 12VDC power supply a regulated 12.0 volts or a plug in power supply thing for something else? Just remember the heat the LEDs create are absorbed by the LED intself... and if not removed by serious heatsinking, multiple LEDs will burn themselves up.