mxpro32 Posted June 19, 2010 Share Posted June 19, 2010 No matter what I do, my leds keep shorting and not working properly. I thought maybe it was the metal bolts so I switched to all plastic bolts. Then I thought maybe it was the heat transfer paste so I wiped it all off. A bunch of my leds were damaged so I tested each one and made an array using the ones that still worked. Last night it worked fine, but this morning I turn it on and only 1 blue led is working and the 3 white ones (thats all I had left that weren't damaged) were very dim. What the heck is going on? Link to comment
DC5 Posted June 19, 2010 Share Posted June 19, 2010 What are the details of the build? Link to comment
mxpro32 Posted June 19, 2010 Author Share Posted June 19, 2010 They are cree xr-e cool white and royal blue. I figured out this morning's problem: one of the leds (which was working last night) burned out. I skipped it and the rest lit. Hopefully the lack of metal bolts and heat transfer paste will help my next array to not short out. Link to comment
HiepNotik Posted June 20, 2010 Share Posted June 20, 2010 post details about your build and maybe we can help, power supply, wiring ect. make sure your wires don't touch the heatsink itself, make sure all your soldering is good, and please use nylon washers they help from short circuits. and always always use thermal paste, they help transfer heat to the heatsink. without it your heat transfer will reduce dramatically, and causing shorter life on your LED's. Another problem I can think of is, too much power, when too much power is going through the LED's it will burn out. Having it really dim might be because you had too much power and the diod is dying or not enough power. What I suggest is testing your LED's one by one with a battery, when I build mine I tested with my Ultrafire AA Lithium Ion 2.7v battery. make sure you have a battery with enough voltage, or it won't light. Oh and when you do put thermal paste on only very very little is needed grain of rice or even lesser, because when you screw it down it will come out the sides and you don't want it everywhere. I'm gonna subscribe to this thread see if I can help you, because I understand that LED's are expensive and I hate to see you go through so many. Link to comment
doctaq Posted June 20, 2010 Share Posted June 20, 2010 what are you using to drive them and what current are you running at? shorts generally wont toast your leds just your driver Link to comment
blasterman Posted June 20, 2010 Share Posted June 20, 2010 I build a lot of arrays on the side, and the biggest thing I've found that causes shorts is sloppy soldering. Even a tiny piece of molten solder touching the side of a star can cause you to chase a short for days. Add some salt spray and things get annoying really fast. This is why I think we need another format to work with other than stars, but haven't found one. When I'm done soldering things, and the array tests out good with a burn in, I'll go back over and put some epoxy over all my solder joints for extra securing and 'weather proofing'. This helps tremendously. Also, a shorted LED will often fail with a current regulated driver because the driver constantly hits that LED with full voltage as it discharges, and this eventually kills it. So, either way, the offending LED gets removed from the equation. Link to comment
mxpro32 Posted June 20, 2010 Author Share Posted June 20, 2010 The driver is the Meanwell ELN-60-48D that nanotuners sells. I think I had too much heat transfer paste. I was using arctic silver which is conductive, and the metal bolts. I'm redoing the whole array with the remaining good leds, and new ones to replace the ones that burned out. I'll be using less heat transfer paste and nylon bolts ( I was already using plastic washers). My solder joints are clean ( I have to solder all the time for work). It just seems like I'm always chasing shorts. Link to comment
jm82792 Posted June 20, 2010 Share Posted June 20, 2010 I will keep all of this in mind because I do not wish to screw up my array. So I am assuming make sure the arctic silver isn't touching anything, use nylon washers and and make sure your solder job is A+. Link to comment
Zepo. Posted June 20, 2010 Share Posted June 20, 2010 I will keep all of this in mind because I do not wish to screw up my array.So I am assuming make sure the arctic silver isn't touching anything, use nylon washers and and make sure your solder job is A+. Yes, arctic silver is extremely conductive. Link to comment
farkwar Posted June 20, 2010 Share Posted June 20, 2010 what are you using to drive them and what current are you running at? shorts generally wont toast your leds just your driver Voltage on LEDs only go one way. Right? They are diodes., right? Link to comment
jm82792 Posted June 20, 2010 Share Posted June 20, 2010 Can I remove arctic silver with alcohol and a lint free cloth? In the future doesn't the alumina stuff sound better since it's far less conductive? Link to comment
doctaq Posted June 20, 2010 Share Posted June 20, 2010 yes voltage only goes on way in an led array, but with shorting and unpredictable resistances the voltage/current limits of the driver may be exceeded Link to comment
thewire Posted June 21, 2010 Share Posted June 21, 2010 Pictures would definitely help most expert in here (not me!). Also how you wired the LEDs and etc Link to comment
Uncitw2b Posted June 21, 2010 Share Posted June 21, 2010 I dont know if you need nylon bolts as well. From what my understanding (but I am no expert by any means) was is that the bolts can help with heat transfer as well. The nylon washer is enough to prevent the shorts by contact with the bolts. Link to comment
doctaq Posted June 21, 2010 Share Posted June 21, 2010 screwing down the star provides pressure which will aid in heat transfer but a metal screw should almost definateley not be a problem with a nylon washer Link to comment
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