Flickering LEDs

  • Thread starter Watson A.Name - \"Watt Su
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Watson A.Name - \"Watt Su

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I mounted 15 cheapo Hong Kong white LEDs on a protoboard last year and
ran it for awhile with about 25mA thru each LED. I didn't have it
running for months like I usually do, and it's been sitting around for
awhile.

I connected it up to a PS and with the current set at about 20mA,
several of the LEDs started flickering. First one, then a few more
started flickering at a few times a second, some completely on and off,
others just barely perceptible. Finally a few of the flickering LEDs
just quit completly, so I replaced a couple with some of the same
(unused) HK LEDs. The unused ones are much brighter than the rest, so
it's plainly evident that the LEDs deteriorated with whatevr use I gave
them last year.

I've run other white LEDs for long periods, and this is the first time
I've ever sen them flicker. Must be those cheapo Hong Kong LEDs.
Weird.


--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
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My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
"Watson A.Name - \"Watt Sun, the Dark Remover\""
<NOSPAM@dslextreme.com> wrote:
I've run other white LEDs for long periods, and this is the first time
I've ever sen them flicker. Must be those cheapo Hong Kong LEDs.
Click to expand...
You seem to know a lot about LED quality and lifetime, what's a good
choice for night-light LEDs around my house. Cost is (essentially) no
object, as mounting them and wiring them will suck up enough of my
time that the cost of the LEDs will pale in comparison. Lumiled
Luxeon Star Hex is my current choice...

Thanks!
 
"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:
I mounted 15 cheapo Hong Kong white LEDs on a protoboard last year and
ran it for awhile with about 25mA thru each LED. I didn't have it
running for months like I usually do, and it's been sitting around for
awhile.

I connected it up to a PS and with the current set at about 20mA,
several of the LEDs started flickering. First one, then a few more
started flickering at a few times a second, some completely on and off,
others just barely perceptible. Finally a few of the flickering LEDs
just quit completly, so I replaced a couple with some of the same
(unused) HK LEDs. The unused ones are much brighter than the rest, so
it's plainly evident that the LEDs deteriorated with whatevr use I gave
them last year.

I've run other white LEDs for long periods, and this is the first time
I've ever sen them flicker. Must be those cheapo Hong Kong LEDs.
Weird.
Click to expand...

As a former Mfg Engr and Assurance Engr I've often thought it would be really
interesting (and mebbe humorous) to visit the mfg lines of certain eastern
companies and observe the various processes. It wouldn't surprise me at all to
see a worker eating lunch in the clean room or stacks of PCB panels on a bare
floor before etch. It truly amazes this western observer that the lowest-tech
houses ever manage to ship functional product; their MEs must be wizards.
 
<William P.N. Smith> wrote in message
news:fb4m21dseod7hnhi0t5qbmhcvok6oqqtoq@4ax.com...
"Watson A.Name - \"Watt Sun, the Dark Remover\""
NOSPAM@dslextreme.com> wrote:
I've run other white LEDs for long periods, and this is the first
time
I've ever sen them flicker. Must be those cheapo Hong Kong LEDs.

You seem to know a lot about LED quality and lifetime, what's a good
choice for night-light LEDs around my house. Cost is (essentially) no
object, as mounting them and wiring them will suck up enough of my
time that the cost of the LEDs will pale in comparison. Lumiled
Luxeon Star Hex is my current choice...
Click to expand...
Yeah, most people don't realize that their time s worth a certain
something. Then they try to build a few more after the 'one-off' and
find with stark realization that they really should be counting their
hours as dollars.

I have several LS lights around, mostly NW98s. I think I'm gonna order
a couple Luxeon Star side emitter replacements for the incandescent
lamps in my Mini Maglites. But I think they're a bit expensive for
night lights. And I think that it would be better to have a wider,
distributed light source for a night light; I'd use several 5mm LEDs
like the Nichia NSPW510s with the LED mounted at different angles to
distribute the light evenly over a wide area.
http://www.nichia.co.jp/specification/led_lamp/NSPW510BS.pdf but you can
buy them for a buck apiece here. http://www.whitelightled.com/

The two Hong Kong LEDs that I've had on 24/7 since July (over 5500
hours) have pretty much gone dim, but the two Nichias in series with
them are still fairly bright. I've never had a Nichia go flakey like
these HK cheapos. I got them on Ebay, and I think the sellers sell a
lot of seconds there, even rtho they claim otherwise.

> Thanks!
 
"R.Lewis" <h.lewis@connect-2.co.uk> wrote in message
news:390ibfF5ta247U1@individual.net...
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote
in message news:112luiiac9jjr38@corp.supernews.com...
I mounted 15 cheapo Hong Kong white LEDs on a protoboard last year
and
ran it for awhile with about 25mA thru each LED. I didn't have it
running for months like I usually do, and it's been sitting around
for
awhile.

I connected it up to a PS and with the current set at about 20mA,
several of the LEDs started flickering. First one, then a few more
started flickering at a few times a second, some completely on and
off,
others just barely perceptible. Finally a few of the flickering
LEDs
just quit completly, so I replaced a couple with some of the same
(unused) HK LEDs. The unused ones are much brighter than the rest,
so
it's plainly evident that the LEDs deteriorated with whatevr use I
gave
them last year.

I've run other white LEDs for long periods, and this is the first
time
I've ever sen them flicker. Must be those cheapo Hong Kong LEDs.
Weird.


'Hong Kong leds' is a bit vague.
Who is the manufacturer, what is the type number (etc.)?
Click to expand...
To ne honest, I don't know who made them, but the seller doesn't sell on
ebay anymore, probably because of the reputation for the cheap crap they
sold. They were rated at 3000 mCd, 20mA, but the 3000 was, instead of
typical, more like maximum, with the typical something like 1500 to
2000. So the seller lied. And I've run them at 20mA and they are going
dim after only 5000 hours. So they lied about howe long they last. :-(

I came across a datasheet for a 5mm white led (a bit under a year ago
but
now can't put my hands on it) that had a max continuos DC current
rating of
19mA.
You don't forget numbers like that too quickly.
Click to expand...
Another number I came across the other day. Back in March 26, 2001 I
purchased my first white LED from Rat Shack, paid an outrageous five
bucks for it. I soon began to look for more reasonable prices for them.
I went by one electronics store and they wanted even more than Radio
Scrap(!) So I started looking online for them. Now the shyster sellers
on ebay will sell them for nearly nothing, but they hit you with a ten,
fifteen or more dollar shipping charge, which brings the price up to
about a quarter apiece. Turkeys.
 
On Sun, 06 Mar 2005 16:09:09 GMT, the renowned Michael
<NoSpam@att.net> wrote:

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

I mounted 15 cheapo Hong Kong white LEDs on a protoboard last year and
ran it for awhile with about 25mA thru each LED. I didn't have it
running for months like I usually do, and it's been sitting around for
awhile.

I connected it up to a PS and with the current set at about 20mA,
several of the LEDs started flickering. First one, then a few more
started flickering at a few times a second, some completely on and off,
others just barely perceptible. Finally a few of the flickering LEDs
just quit completly, so I replaced a couple with some of the same
(unused) HK LEDs. The unused ones are much brighter than the rest, so
it's plainly evident that the LEDs deteriorated with whatevr use I gave
them last year.

I've run other white LEDs for long periods, and this is the first time
I've ever sen them flicker. Must be those cheapo Hong Kong LEDs.
Weird.


As a former Mfg Engr and Assurance Engr I've often thought it would be really
interesting (and mebbe humorous) to visit the mfg lines of certain eastern
companies and observe the various processes. It wouldn't surprise me at all to
see a worker eating lunch in the clean room or stacks of PCB panels on a bare
floor before etch.
Click to expand...
Yeah, a walk-through can tell you a lot. I estimate that 80-90% of
problems could be anticipated by having an experienced (in the
production processes) engineer, not even a QA guy, poke around the
facility. I've seen PCB panels on open-air racks in dirty environments
(resulting in hairline shorts between traces), fine mechanical
assemblies being done by subcontract housewives in uncontrolled
conditions, poorly maintained equipment, lax qc control etc. etc.
There are also some very well run factories, and the catch it that
it's hard to tell the difference from just looking at the samples
(which may or may not be made in the same conditions as the production
run). They are usually quite willing to have foreign buyers look at
their operations, but are much more suspicious about locals- with some
justification (I've actually had offers to do industrial espionage for
competing comanies, which of course were declined).

It truly amazes this western observer that the lowest-tech
houses ever manage to ship functional product; their MEs must be wizards.
Click to expand...
One of my friends in HK who has their production on the mainland says
he must deal with much cheaper locally invested competition that ships
10-20% bad product. That's acceptable in 3rd world countries, where
the labor to find the bad ones is very cheap. Similarly, one of the
semiconductor suppliers I deal with has a cheaper product with no QC
for the India etc. market. I also know a well-known US semiconductor
company that sells their chips "untested" at very low prices for the
China market. There are probably more of them doing it.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
i too believe the ones on ebay are seconds. i picked up a bag of rgb
leds. lined them up on a board in a straight line. as you power up
each color, it is easy to see that the chips are all over the place
inside the package. red seemed to be skewed the most causing the
viewing angle to be way off to one side.
 
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com> wrote
in message news:112luiiac9jjr38@corp.supernews.com...
I mounted 15 cheapo Hong Kong white LEDs on a protoboard last year and
ran it for awhile with about 25mA thru each LED. I didn't have it
running for months like I usually do, and it's been sitting around for
awhile.

I connected it up to a PS and with the current set at about 20mA,
several of the LEDs started flickering. First one, then a few more
started flickering at a few times a second, some completely on and off,
others just barely perceptible. Finally a few of the flickering LEDs
just quit completly, so I replaced a couple with some of the same
(unused) HK LEDs. The unused ones are much brighter than the rest, so
it's plainly evident that the LEDs deteriorated with whatevr use I gave
them last year.

I've run other white LEDs for long periods, and this is the first time
I've ever sen them flicker. Must be those cheapo Hong Kong LEDs.
Weird.


--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
Click to expand...
'Hong Kong leds' is a bit vague.
Who is the manufacturer, what is the type number (etc.)?

I came across a datasheet for a 5mm white led (a bit under a year ago but
now can't put my hands on it) that had a max continuos DC current rating of
19mA.
You don't forget numbers like that too quickly.
 
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