LED Failure Rate

[GHD]

I'm pleased to report that both suppliers of the LED's that failed willingly replaced them. I suspect there were quality control issues in both cases. Stay tuned as the heavy use season is approaching.

[JeffPo]

Sturgeon-Phish,

I've got a Coleman pop-up camper.  Sometimes I camp where there are no power hookups.  In those cases, I run my lights (or anything else) off a 12volt battery.  The normal 12v camper bulbs (#1141 & #1156) can pull 2 amps of power.  I've replaced mine with LED versions.  The LED version has the same base, but instead of the incandescent bulb it has a cluster of LEDS.  Now we're down in the 100 milliamp range!  I've got white ones and red ones (to protect my night vision while star gazing).  I got them from:

http://www.superlumination.com

They work great!

 

[lionelsoni]

LEDs act more or less like constant-voltage devices in the "forward" direction.  That is, the voltage drop across the device is very insensitive to the current through it; but the current is exquisitely sensitive to voltage.  Therefore, they are usually operated in series with a "ballast" resistor and supplied from a voltage at least somewhat greater than the LED's forward voltage.

The forward voltage ranges from about 1.5 volts to 3.5 volts depending on the color of the LED, with infrared and red being lowest and blue highest.  (White LEDs are just blue ones with some phosphor added to fill in the spectrum.)

Most LEDs are rated at no more than 20 milliamperes forward current.

More than a few volts in the "reverse" direction will destroy an LED.  Below that voltage, it acts pretty much as an open circuit, and doesn't emit any light.

A device intended as a replacement for an incandescent lamp should have, as a minimum, a ballast resistor that provides the LED with a suitable current for the maximum operating voltage of the entire assembly, and protection against reverse voltage, especially if it is intended for use on an AC circuit.

[Sturgeon-Phish]

JeffPo, LEDs for your camper?  Tell me more please.

[superwarp1]

LED should last you 100,000 hours and should never fail if installed and current limited correctly.

Do the LED that have failed for you already have a current limiting resistor installed with them?  If so I'm wondering if they have been over heated with a solder iron.

Gary

[SteelMonsters]

If an LED turns on bright red and it's not a red LED, then it's time to buy a new one.

LEDs are current controlled devices. I could care less how much voltage you give it as long as the current is okay.

The two things that you need to know is how much current the LED is rated for and how much your giving it. If you give an LED more than it's rated for then you can be sure that it will not last long.

[JeffPo]

I haven't used any LEDs in my railroad hobby, but I have used them in my astronomy hobby.  I've only had one "fail" on me and that was because I put power to it without a resistor.  :)

I've replaced the bulbs in my camper with LED bulbs to make my battery last longer.

 

[lionelsoni]

An LED used within its ratings should last pretty much forever.  So I imagine that the designer of the incandescent-replacement gadgets messed up.

[GHD]

LED's are in the current edition. The other supplier was covered in a previous edition. So far I've seen no data or discussion on life,especially at higher voltages, except general comments that they should survive OK but at a reduced life span. I was hoping to get some feedback from users.   

[Buckeye Riveter]

Didn't CTT do an article on LEDs ?  Anyone remember the issue? 

[csxt30]

I was just reading an article today about the future of LEDS for the home. They said they are making bulbs for the house & cost abot 60 dollars right now & would last 10 thousand hours. it said how much more effecient leds are than other lights. Other lights have all their energy going up in as heat. They didn't say too much about the leds for our use. Just thought I'd pass that on  !!

Thanks, John  

[GHD]

I have a lot of lights, over 70 Lionel switches, to power. The LED bulbs provided a great solution to reducing the power required. I purchased my first LED's at the York Spring meet. The failure rate on those so far is about 10%. I since purchased more of the less expensive variety and the failure rate on them is around 25%. I normally operate them at minimum voltage( 6-9 ) and turn them up to14-16 volts when throwing a switch. I do really like the LED's but wonder how long they will last. I'm interested in feed back.