Fried LED. WHY?

**Eco** · 01-02-2009, 03:56 PM

The Lux III Red LED I got from the shop died, or rather, it never lit.
The first thing I did to it was solder it to some quick connects on the heatsink, then attach it to my Lux V saber, which was running a 1000ma puck, so that shouldn't have fried it.
The weird thing is, when I use my multimeter to test the continuity, it says it's open, but when I set my multimeter to the voltage setting, I'm able to run .4v through the LED.
How can a circuit be open and yet still have a current ran through it?

**Jedi-Loreen** · 01-02-2009, 04:24 PM

You put it in your Lux V saber? What voltage is it using? If you're using a Buck Puck, like I think you are, it shouldn't be an issue. I suppose it could be burned out, but still pass voltage through it, though. Kind of like a lamp on a string of Christmas lights will still pass current through it even when it's burned out, so that the rest of the lamps in the string will light.

Is your Quick Connect wired correctly? Tim had a bunch that were twisted 180 on one end.

An LED is a diode, so it will only read closed in one direction. I just metered my Lux III cyan, and the continuity test actually had enough voltage to light it up dimly, that surprised me.

**Eco** · 01-02-2009, 05:33 PM

Yes, I'm using a 1000ma Buckpuck on my Lux V setup, which was running at 9v. I asked the question on this forum several times if it would be a problem to switch the actual LED from a Lux V to Lux III without changing the rest of the setup and I received the OK from both you (I believe) and Novastar.

I don't think it was the quick connect, I was using the new JST connectors, which have the red/black leads. Just to be sure I switched the quick connect out with another one, as well as just applying hot leads to the LED.
Bubkiss.

Okay, the christmas light analogy explains the multimeter data.
But the LED doesn't read closed in any direction, I even tried flipping the testing diodes around so it was + to -, just in case that, somehow, the LED emitter was placed onto the star backwards on the assembly line.
Zilch.

As far as what I've done to it, I'm positive that I didn't actually touch the bubble of the LED with my soldering iron. I did drop it from my lap to the floor of my truck, but that couldn't have been more than two feet, and the cab is carpeted. I suppose I may have had my iron to the leads for too long, causing the emitter to heat up, but that's it.

**Arm on Fire** · 01-02-2009, 06:02 PM

Reds and Red-o's are notorious for shorting out if you dont use thermal tape or paste between the LED and the heatsink. it somthing about how they are produced I think they are grounded to the star base or somthing and it causes a short.

**tinfoilhelmet** · 01-02-2009, 09:11 PM

bzzzt

**Jedi-Loreen** · 01-02-2009, 10:05 PM

Oh yeah, I forget about the problems that people have with the red Lux IIIs. I've wired up a good half dozen of the reds, and have never heard of a problem with any of them. I think that's more prevalent with the red/orange LEDs. I haven't used any of those, yet.

**Novastar** · 01-03-2009, 01:08 AM

I've used TONS of the reds, red-Os... the only grounding issues I've had were putting together two separate circuits (for a staff) where both circuits could have minor contact with the hilt.

In this case... can you believe one of the LEDs was shorting out via the SWITCH BODY OF ITS CIRCUIT?!?! That is to say... the little metal casing on the latching switch body (which NATURALLY was fashioned to the hilt)... was the cause of the problem.

The Li-Ion cells + PCB saved my butt during troubleshooting... never "killed" anything, just shut the circuit down. When I fixed it... the LED was just fine.

However... I also use heatsink paste / thermal paste under all of my LEDs... and so this may or may not help, since they still "grounded out" (to short... sorry, bad baseball joke).

EDIT: For reference... hmm... my switches were on the NEGATIVE (ground) line in the circuits... so... hmm, I wonder if they were on the POSITIVE line if the same grounding issue would have occurred... well, hope it helps someone.

It would appear thermal tape is the best bet... or isolate the LED & heatsink from the hilt itself. Now THERE'S a conundrum...

**Maxepane** · 01-03-2009, 08:07 AM

Nova, maybe make a heatsink mounting bracket out of PVC?

**Darth Morbius** · 01-03-2009, 02:59 PM

Originally Posted by Eco

As far as what I've done to it, I'm positive that I didn't actually touch the bubble of the LED with my soldering iron. I did drop it from my lap to the floor of my truck, but that couldn't have been more than two feet, and the cab is carpeted. I suppose I may have had my iron to the leads for too long, causing the emitter to heat up, but that's it.

Carpeted cab in a truck? I would say you have fallen victim of ESD my friend.

Vehicles are notorious for static charge buildup. Was the LED bare? As in not in an anti-static bag?