What makes 5mm LEDs last longer?

I have made some night lights using 5mm LEDs. I keep the current low but what else can I do to make the LEDs last longer? I get about 4 to 6 months on them.

Thanks

Make sure that the output current to the LEDs is true DC, or something very close to it. Spikes are bad for LEDs, regardless of the mean or RMS current.

add some heatsinking either by soldering a piece of aluminum on one of the legs or don't clip the led's legs when you solder it, assuming of course you use bare LEDs for your projects.
5mm LEDs create heat over time much like their big brother luxeons and CREEs, its this heat that causes many of the premature failures.

Also, what color of LEDs are you using? depending on the color the required current and voltage specifications differ, so you may be overdriving some while underdriving others

Illum_the_nation said:

add some heatsinking either by soldering a piece of aluminum on one of the legs or don't clip the led's legs when you solder it, assuming of course you use bare LEDs for your projects.

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Soldering uncoated aluminum is impossible. Use copper to do that instead.

My own opinion is that a 5mm LED can't be heat sinked sufficiently to save them. They were designed primarily to be seen, rather than to project.

I've noticed the same thing with the commercially prepared nightlights, especially the 4, 5 and 7 watt screw in candelabra based LED bulbs. Of those, I've tried the ones from Walmart, Target, Walgreen and a couple I've mail ordered. They all dim so much after a few months, that other than power savings, you'd just as well use conventional incandescent. The one from Walgreen does seem better than the rest, but they also contain three LEDs instead of one.

We may have to wait for a redesigned 5mm, or make use of one of the higher power ones like a Luxeon or such. they were designed with a view toward a heatsink.

Anyway, I'd think cutting power to them is about all that's available.

LukeA said:

Soldering uncoated aluminum is impossible. Use copper to do that instead.

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1) Use Nichia brand.
2) Do not over power the LEDs
3) Do not cluster them too closely together.

Would a 3mm or 7mm or 10mm last longer?

Thanks for all the info so far.

Where does one buy Nichia brand LEDs at a good price?

Thanks

eebowler said:

1) Use Nichia brand.
2) Do not over power the LEDs
3) Do not cluster them too closely together.

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Well powering a high power LED at the current might work too. If you are at a low enough current, the slug of the LED would be enough to dissipate the heat.

<20ma

There are a few 5mm LEDs that run above 20 mA but at 20 mA, you should be safe running just the bare LED(has anyone tasted this?).

Many of the better high power LEDs are also pretty efficient at such low currents. the current gen ones go over 100 lumen/watt at 20 mA(the Cree XR-E Q5 hits around 120). The best I've read from a 5mm LED is around 85 lumen/watt.

As for making the 5mm LEDs last longer, besides the above suggested things, try running a lower current if possible.

ken2400 said:

I have made some night lights using 5mm LEDs. I keep the current low but what else can I do to make the LEDs last longer? I get about 4 to 6 months on them.

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I'm going to preach heresy here, but I'd advise ditching LED for this use, and switching to neon.

But if you absolutely cannot bring yourself to stoop to 100+ year old vacuum tube technology, then try an array of more LEDs driven at much lower current.

Or a few power LEDs runing at low current.

I don't mean to drop in and have my post look like an advertisement, but I too once shared the frustration of being unable to find decent LED replacements for the incan nightlight bulbs that burn out every few months (or weeks, even).

I was fortunate that I gave the following product a try:

http://eliteled.com/products/lightbulbs/nightlightbulb.html

I purchased two of these in "cool white" over a year ago (my records indicate June of 2007). Since receiving them, they have been on continuously inside regular incan nightlight fixtures for 16 straight months. I recently bought a few more and, comparing the brightness of the 16 month old LED nightlight bulbs with the new ones, I would guess there has been about a 20% reduction in output. That's a guess because I have no measuring equipment and also because there may have been improvements in the output since then (although I am not aware of any).

The cool white ones have a slightly bluish tint, whereas it looks like the warm white ones are more "daylight" like in tint, but I don't own any of the warm white ones (yet). I find the output somewhat less than a typical 4W incan nightlight bulb, but the output of the cool white LED bulbs is much, much more pleasing (to my tired old eyes) than the sickly yellow output of the incans.


Cool White LED bulb


Warm White LED bulb

At $6.95 each, they are not cheap. But I can now put a nightlight wherever I want without having to bother with constantly needing to replace the incan bulb (and when you notice that the incan bulb has burned out, it is almost always because you needed the light but found it nonfunctional).

I tried LED replacement bulbs from WalMart. They were selling for $3 for a pair, but of the six I put in use 5 months ago, two have burnt out and the other 4 are so dim as to be of little use other than as "markers" to keep me from bumping into the wall (which, you know, I don't generally do anyways, nightlight or no).

Europium, Those look like the ones I got at Target. They have a white base with clear dome. Inside they have a white LED in the center with 4 diodes and a resistor around it. It gets rather warm in use. One has developed a condensation like coating on the inside of the dome after a few days of use. I don't think they are all the bright, but it has not dropped in output any after a week as compared to the second unused one. They come in a 2 pack for 3 or 4 bucks at Target. I don't recommend them.

I have went through one walgreens 3led nightlight so far in about a year. I should have saved it and just replaced the LEDs next time one goes out I am going to crack it open and put a luxeon I pulled out of a cheap light in it I bet it would last a lot longer. I wish they made cheap sockets for 5mm LEDS that would make it easy to just replace them when they get dim IMO

Keep your old Luxeon/Cree emitters after a flashlight upgrade. They work awesome as a 5mm replacement in night lights. I just let them hang out in air, no need to heat sink at this low of current. They start and stay bright white, instead of going murky purple.

ken2400 said:

I have made some night lights using 5mm LEDs. I keep the current low but what else can I do to make the LEDs last longer? I get about 4 to 6 months on them.

Thanks

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What is low current? I recommend driving them at 10-15ma and using more of them to reach the required output. They are more efficient at lower currents anyway. 5mm are not expensive from the right source and the China cheapies are not bad like they were a couple years ago.

Keeping them cool is important and the lower current helps. Mount them on the PC board so some heat will dissipate into the board.

JohnR66 said:

Europium, Those look like the ones I got at Target. They have a white base with clear dome. Inside they have a white LED in the center with 4 diodes and a resistor around it. It gets rather warm in use. One has developed a condensation like coating on the inside of the dome after a few days of use. I don't think they are all the bright, but it has not dropped in output any after a week as compared to the second unused one. They come in a 2 pack for 3 or 4 bucks at Target. I don't recommend them.

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I understand. The ones I bought from WalMart look nearly identical, on the outside, to the EliteLED bulbs you see in the images I posted.

THEY ARE NOT THE SAME, YOU CAN BE CERTAIN.

However, based on the ***** performance, I would not be surprised to learn that the WalMart bulbs that I bought are the same model that you bought at Target.

But the EliteLED nightlight bulbs (which have 3 LEDs in them) REALLY HAVE LASTED OVER 11,000 HOURS (so far!), having been constantly on since June of last year. They are not as bright as the 4W incan bulbs, but they are easier on my eyes. I realized after I bought them that I did not need the brighter, yellower output of the incans.

The reason I bought several more EliteLED bulbs just a couple of weeks ago (at $7 apiece) is because the WalMart LED bulbs were a rip off--even at the much lower price of two for $3--and because those two EliteLED bulbs I bought last year JUST KEEP ON GOING, AND GOING, AND ... well, you get the picture, I hope.