LED's do burn out!

LED\'s do burn out!

I'm not speaking of failure from over current either...

I have a SCSI enclosure that has a 10 candela led for each hard disk. They will fire whenever there is activity on the bus.

The LED for drive number two look significantly dimmer than the other LED's. I didn't really pay attention until yesterday when I noticed it wasn't firing at all!

Sure enough, the connectors are tight. I removed the plug going to LED1 for drive 1 and when plugged into drive 2 it fired! The friggin' LED burned out! It's about 1 1/2 years old. Never thought I would see this before.

FWIW!

-DAK-

Re: LED\'s do burn out!

In my experience LEDs don`t just burn out overnight, but rather, they fade away.

I`m a fire alarm engineer by day. The company I work for has been producing fire alarm parts and systems since 1962 and made its first electronic control panels featuring some LED indicators in 1978. Some of these are still in use today. In all the ones I`ve seen, the green DC On LEDs which have undoubtedly remained lit for most of the 25 years they`ve been there are still glowing.

One panel I have in my little "fire alarm museum" collection is about 20 years old, and has 2 green LEDs inside. One DC On light and one Fast Charge light for the internal backup batteries. The Fast Charge light rarely if ever glows on this particular model (only following a power cut or the installation of new, discharged batteries), but the DC On one is lit all the time that mains is present. It presents an interesting illustration of the aging of LEDs. The dimming effect over time is drastically noticeable - the DC On lamp that has clocked up some 175000+ hours of glowing is about a third as bright as the Charge lamp (which has probably only seen a few tens of hours glow at most), and is a slightly more "burnt" yellower green colour too. But it`s still glowing and can be seen easilly in most ambient light conditions.

I don`t think any LEDs that aren`t faulty or abused would ever "burn out" in the traditional sense of the word. They will just keep on growing dimmer and dimmer until the human eye can no longer sense the glow.


Sounds like you got a defective LED in your drive bay there! That, or the conditions for it aren`t nice - too much current or heat perhaps.

/ubbthreads/images/graemlins/eek.gif

Re: LED\'s do burn out!

I would check your thermal situation, but Mean Time Between Failure is a statistical measurement; there are some LEDs that just die several statistical deviations away from the norm. That you got better than a year of life makes it less than wildly unlikely that the LED would fail. Technically this is a parts failure and if your SCSI drive is still under warranty, you should be able to get it replaced.

Re: LED\'s do burn out!

I agree with Chris M.; LED life is measured in half lifes anyway. However ESD damage is real and not necessarily catastrophic. I understand that even keyboards can suffer from ESD damage and at some point with enough accumulated damage, give up the ghost. I suggest this simply as a possible cause.

- Don

Re: LED\'s do burn out!

[ QUOTE ]
Chris M. said:
I don`t think any LEDs that aren`t faulty or abused would ever "burn out" in the traditional sense of the word. They will just keep on growing dimmer and dimmer until the human eye can no longer sense the glow.


Sounds like you got a defective LED in your drive bay there! That, or the conditions for it aren`t nice - too much current or heat perhaps.

[/ QUOTE ]

I concur.
Some of the backlit switches in my car (97 Jetta) are green 12V LED's, I had one become intermittant then go out altogether. Before I knew it was an LED, I'd tap on the switch, to no avail, it would come & go as it pleased.
I disassembled the switch, discovered what it was, and replaced it with another 12V LED, so far so good. The 'dead' LED was bad, not just a crummy connection anywhere.
I presume the original was defective or at least destined to a short life right from birth. /ubbthreads/images/graemlins/icon23.gif Ah well, easy $2 fix instead of new switch from VW.

Re: LED\'s do burn out!

Thermal conditions are ideal. (20°C) Current is limited. This is far from CW. The LED's flicker like crazy, occassionally all of the LED's glow from very dim to full brightness depending on how the array is getting accessed.

The RAID controller has a large battery backed up cache that flushes to the drives every ten seconds. The LED's are full ON when a flush occurrs. I had a PV array next to the box one time and couldn't believe the signals I was getting so I plugged it into my Mackie and recorded it.

atlantis.shuttleteam.com main array engine cache flush

Pretty neat. I guess this is why people should NOT have their indicator LED's near a window! People can steal your information if they can get enough signal from those flickering LED's!

-DAK-

Re: LED\'s do burn out!

Wow, that sounds just like a 1200 or 2400 baud modem, if you're old enough to remember them. Try putting an AM radio near the SCSI cable. Similar noises.

There was a green LED on the office FAX machine that was very noticeably dimmer at about 10 years old, kept getting gradually dimmer, and then one day, at about 12 yrs old, suddenly just went out.

Re: LED\'s do burn out!

LOL, my computer days go back to punchcards unfortunately. /ubbthreads/images/graemlins/frown.gif

I have a lamp made with an array of Nichia's and a rectifier diode. They run off 120VAC with no filtering and the flicker is perceiveable as a NE2 neon, perhaps more. They have been on since 03/02/2000 and never been turned off. Roughly 30k hours on them. The half-wave rectified AC doesn't seem to hurt them.

-DAK-

Re: LED\'s do burn out!

i wonder how much of the loss of brightness is due to degradation of the plastic?
found a led in a control board for a studer grinder that was brown from the die cup forward.no evidence of overheating either.this is a power on indicator.the fault indicators look normal.

[ QUOTE ]
Chris M. said:
In my experience LEDs don`t just burn out overnight, but rather, they fade away.

I`m a fire alarm engineer by day. The company I work for has been producing fire alarm parts and systems since 1962 and made its first electronic control panels featuring some LED indicators in 1978. Some of these are still in use today. In all the ones I`ve seen, the green DC On LEDs which have undoubtedly remained lit for most of the 25 years they`ve been there are still glowing.

One panel I have in my little "fire alarm museum" collection is about 20 years old, and has 2 green LEDs inside. One DC On light and one Fast Charge light for the internal backup batteries. The Fast Charge light rarely if ever glows on this particular model (only following a power cut or the installation of new, discharged batteries), but the DC On one is lit all the time that mains is present. It presents an interesting illustration of the aging of LEDs. The dimming effect over time is drastically noticeable - the DC On lamp that has clocked up some 175000+ hours of glowing is about a third as bright as the Charge lamp (which has probably only seen a few tens of hours glow at most), and is a slightly more "burnt" yellower green colour too. But it`s still glowing and can be seen easilly in most ambient light conditions.

I don`t think any LEDs that aren`t faulty or abused would ever "burn out" in the traditional sense of the word. They will just keep on growing dimmer and dimmer until the human eye can no longer sense the glow.


Sounds like you got a defective LED in your drive bay there! That, or the conditions for it aren`t nice - too much current or heat perhaps.

/ubbthreads/images/graemlins/eek.gif


[/ QUOTE ]

Re: LED\'s do burn out!

<font color="800080">i wonder how much of the loss of brightness is due to degradation of the plastic?</font>

<font color="800000">I`ll have another look at it on Monday, but I`m pretty sure the resin hasn`t discoloured at all. It`s a pretty pale green to start with and both lamps looked the same from the front as far as I can remember.

I have seen a fair few discoloured red LEDs though - translucent-red ones that have been faded almost clear by the sun and diffused ones that have turned brown, but were otherwise still working. These were in emergency light fixtures, exposed to sunlight and often subjected to high internal ambient temperatures too - inefficient circuitry trickle-charging the batteries or preheats on the ends of the flourescent tubes to ensure they strike when required (e-lites in this country are usually 8 watt flourescent bulkheads driven by NiCad batteries, though the US style spotlight kind is seen here too, where a larger area needs to be lit). Surviving 5 - 10 years in those conditions is pretty good going for LEDs.

For some reason we deal with emergency lighting though the connection with fire detection equipment is a mystery to me at the present......</font>

/ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/grin.gif