Luxeon Star

I just got a Luxeon star today. I got it to smoke, now it's in the garbage. What I need to know is do I need a resistor or did I use too much power? I used 4 AAA batteries. /ubbthreads/images/graemlins/mad.gif /ubbthreads/images/graemlins/mad.gif /ubbthreads/images/graemlins/mad.gif

WAAAAAAAAA....WAAAAAY too much voltage and power!

Welcome to cpf...the thoughtful learning station on your Internet dial.

Check the spec on the Luxeon and it will tell you the Vf of the light. As a general rule just feed it the Vf plus a little more (20% more to be safe) and it will outlast you.

Isn't it much preferred to control the current, at 350ma or below for a 1W?

Don't forget the heat sink if over drive it.

Are you sure it's smoked? Wimpy AAA's can't supply that much current. I once drove a 1W low dome to about 3.5A for several seconds. It didn't smoke but it definitely was changed forever /ubbthreads/images/graemlins/grin.gif People have been routinely driving 1W's at close to an amp but as desmondpun states, heatsinking is critical.

CM: my single AAA nimh can pull 7 Amps!

Heatsinking is also key. Say you just have an emitter and
you drive it at 350ma (one half the spec) but without heatsinking.
I guarantee it'll burn it in about 1-2 minutes.

magic smoke /ubbthreads/images/graemlins/grin.gif

vasdef: sounds like you need to head over to the Flashlight Electronics section and take a few Electronics courses at the CPF University! Do you have any sort of background in electronics?

Admittedly, I don't know too much about electronics, proof is in my previous post. By the way, the Luxeon LXHLMW1C did indeed smoke, and the solder points on it turned brown. I doo have another Luxeon. It's specs are 3.5v 350 mA. So, with 3 AAA's I figured I would use a 3.3 ohm resistor. I won't hook it up until I hear a reply that its ok to continue. Thanks

Mount that star to some kind of an aluminum, or copper plate with thermal compound first.
The same stuff for pc processors ought to do it.
Then try with 2 cells, measure current.
Real low?
Then try 3 aaa with at least a 10 ohm resistor 1st and work your way down to a lower value resistor until you have about 300-350 milliamps showing on your dc amp multitester.
If that multitester came with a temp probe, carefully use that to see how hot your star is getting.

Good luck.

Edit:
Oh yeah;
If you ever decide to use nicad, or nimh batteries, you will need more added resistance 1st.
These things will throw a ton of down home cookin' power through leds that don't have any series resistance added.

I assumed you used alkalines. If you used NiMH, then I would not be too surprised if it smoked. The math to determine currents, resistors, etc is not too hard. You can probably enter it into a spreadsheet and play what-if games. A multimeter (measures current up to 10A as well as the usual) would be beneficial if you're going to tinker, and tinkering is the way to get you started on the road to fun stuff.

I forgot to mention this, but not all luxeons have the same voltage and current.
Since you got stars, there should be a 3-4 character code on the back of it.
If you post it, One of us can tell you the voltage, color tint, and brightness it will likely have.

I checked out the specs on the Luxeon star lxhl-mw1d. It has a forward voltage of 3.42, and mA of 350. I used a resistance calculator, and using 4 AAA alkalines, it suggests a 3.3 ohm 1/2 watt resistor. So...I hooked it up, it's dim as hell. The batteries are new also. I hooked it up without the resistor for a fraction of a second, it looked like a small bright sun. What gives??

I'd appreciate it if someone knew a resolution to this problem. Thanks

[ QUOTE ]
vasdef said:
I checked out the specs on the Luxeon star lxhl-mw1d. It has a forward voltage of 3.42, and mA of 350. I used a resistance calculator, and using 4 AAA alkalines, it suggests a 3.3 ohm 1/2 watt resistor. So...I hooked it up, it's dim as hell. The batteries are new also. I hooked it up without the resistor for a fraction of a second, it looked like a small bright sun. What gives??

[/ QUOTE ]

Sure it's a 3.3 ohm resistor? What voltage are you measuring across the resistor?

Yes, I even used another 3.3 ohm resistor. Unfortunately, my multimeter isn't working right, can't get any readings. /ubbthreads/images/graemlins/mad.gif /ubbthreads/images/graemlins/mad.gif /ubbthreads/images/graemlins/mad.gif /ubbthreads/images/graemlins/dedhorse.gif

the package of resistors says 3.3 k ohm. Is that right?

That is 3,300 ohms. The "k" stands for thousands. 3.3 times 1,000 = 3,300 ohms. You are way too high on the resistance.

3.3 KELO ohm or 3300 ohm. this would be considered moon mode I believe. 3.3 Ohm might be hard to find in the 1/2 Watt range. Besides, a 1/2 watt will get hot. try 1 watt resistors and see if you can get between 2.7 and 3.5 ohm. A little overdrive shouldent be bad as long as you have some decent heatsinking.

Open to correction if I am wrong.

Jeff

AHA!! I knew something didn't look right. The smallest resistor I have right now is a 100 ohm. It seems to work ok, it's not getting hot. Tomorow I will get the 3.3 ohm resistor. I apologize for my ignorance, and I thank all of you for your help.

No problemo. The cpf detectives are always ready to help. /ubbthreads/images/graemlins/buttrock.gif

With a lower resistance the Luxeon will rock.