1st Mod - I fried the LED. Did I fry the LED?

[icpd30]

I've been on the forum for a few months and have watched with wonder at all the builds and mods. So when all the necessary parts came up for sale, AND I remembered where in the forums to find and purchase them, I pulled the trigger.

Got my heatsink, LED (an SST-50 I think, but don't hold me to that), teflon-coated wire, and 2D Mag. The parts all sat for a while...worries about my abilities and some details of the build kept me frozen in inaction.

About 2 weeks ago, I finally found the time to do this, so I reviewed the forum threads again and got it done. I'm a novice with the soldering iron but managed to get everything together. I slipped in 2 D alkalines just for a quick circuit test. To my surprise it lit up and I shut it off right away. But I was too excited and I lit it up again. This time, after about 5 seconds, the light flickered and then went out. Hmmm.

I took everything apart and gave it an inspection. It looked like my soldering may have been weak on one of the contacts, so I resoldered. I fit everything back together and clicked the Mag switch --- but got nothing. I checked contacts and batteries for about 2 hours before I inspected the LED with a magnifying glass. This is what I saw:

To the experienced it may be obvious, but notice the upper quadrant of the LED, the clear-colored blob surrounding that quarter. Did I apply too much heat during the soldering process and burn the LED? Or what happened?

Thanks for the input.

 

[Der Wichtel]

your LED is fried. It is not a SST-50 but a Seoul P7 LED.
What did you use to mount the LED onto the heatsink? Seem like it is not heat conductive enough so that the LED overheated

 

[ledpwr]

Did you use a way of limiting the current, like a resistor? Because you could have fried the led by allowing it to draw too much current and overheating.

 

[PCC]

Did you use a driver? I don't think that 2D alkaline batteries in a direct-drive configuration would fry a P7 that easily but I could be wrong.

 

[moviles]

Did you use a driver? I don't think that 2D alkaline batteries in a direct-drive configuration would fry a P7 that easily but I could be wrong.

with only 2D alkaline batteries direct-drive really no way to fry a P7 with heatsink, the current draw will be much lower than 2.8 amp

 

[Mettee]

doesnt look like you soldered any wires to the pos side at all. That might be the issue

And that epoxy you used looks scary, if you used regular epoxy and artic alumina something or other that might have cooked it as well.

 

[irv_usc]

doesnt look like you soldered any wires to the pos side at all. That might be the issue

And that epoxy you used looks scary, if you used regular epoxy and artic alumina something or other that might have cooked it as well.

yeah it sure looks like you soldered both + and - to the same side. not good.

 

[icpd30]

Thank you all for your responses.

The photos are post-mortem. I have removed any wires that were soldered, and I double-checked CPF info to make sure I knew + from - so I don't think that was an issue. The other ideas are closer to target I think.

Certainly my soldering was sloppy, and once touched over to both contacts on one side, that is touched both leads (?) or contacts on the same side. My glue was...do I have to admit it...not what I should have used. (That might save me some embarassment.) It probably isolated the LED from the heatsink, not what I should have done - clearly.

It's difficult to bring these mistakes to the forum, everyone seems like such an expert and everything looks so easy. But I know there are many others like me, searching for instructions and guidance, so all you CPFers new to modding, take a second to learn from my mistakes.

All ideas, suggestions, and comments are welcome. Since I am an 'older' adult, I can get over my mistakes quickly - I've had a lot of practice!!!

 

[PCC]

Let me ask you this: if you take 2 alkaline cells in a holder (provided you have something like this) and hotwire the LED do you get light? 3V should be enough to drive the LED at about 100 lumens so don't look at it if you can avoid it or else you will be blinded

 

[beekeeper5]

It's difficult to bring these mistakes to the forum, everyone seems like such an expert and everything looks so easy. But I know there are many others like me, searching for instructions and guidance, so all you CPFers new to modding, take a second to learn from my mistakes.

I'm a new CPFer new to modding and I hear you. Everyday I learn a bit more like using the correct epoxy. I was just planning to use a regular epoxy... :shakehead I'd be interested to find out what exactly happened.

And why is your LED so dusty?!?

 

[PCC]

And why is your LED so dusty?!?

SSC P7 and P4 LEDs have a soft jelly-like lens that is kind of tacky and lint sticks to it like metal shavings to a magnet.

 

[ejot]

It probably isolated the LED from the heatsink, not what I should have done - clearly.

You want the epoxy to conduct thermally but isolate electrically. As you now know, there are epoxies designed to do exactly this. You want as thin a layer as possible of epoxy, ie lots of pressure applied when gluing the emitter.

The slug (metal chunk on the bottom) of the P7 is connected to "+" lead, so you DO actually need to isolate it - electrically. You have to be careful when glueing, because if you press hard/unevenly, part of the slug can contact your heatsink. Two solutions: (1) use an anodized heatsink, or (2) after applying the thermal epoxy to the bottom of the emitter package, lay two pieces of hair (yeah, just pluck it out of your head) across the glue on each end. The two parts will not be able to come closer together than the thickness of the hair.

 

[icpd30]

ppc, thanks for your interest in my dilemna and your clarifying comments. I did try your suggestion, hooking to 2 batteries, but got nothing.

ejot, thank you for the comment. I think that is the problem exactly. I used the wrong type of epoxy, but also worried about the LED slug contacting the heatsink, so I tried to isolate it electrically - but I think I also isolated it thermally. Clearly a No-No.

I'm not giving up, however. I will get the correct epoxy. NOTE TO SELF: in the future, use anodized heat sinks.

Any advice on a driver to use? Seems like I might as well give that a try as long as I am rebuilding.

 

[irv_usc]

if you're going to get another P7, i would recommend the shiningbeam 3mode driver, or the cheapy AMC7135 drivers you can buy from dealextreme.

i particularly like the shiningbeam driver since it gives you a low voltage warning

 

[Import_guy]

Just go to radioshack and pick up a 2D battery holder for less than 2 bucks. It should already have wires on it and buy some alligator clips to attach to wires.Then you can test the p7 directly to see if it is fried. Radioshack has a large variety of battery holders for real cheap if you want to use different batteries to test your p7.