Exceeding LED ratings

[JW]

If so, then you mentioning the above was even more dumb. I said you were
the epitome of stupid, but I underestimated you. You have reached a new
level stupidity that cannot be defined.

I wonder how may angels could dance on his head?

 

[Pimpom]

Hi Pimpom,
Have you tried one or two at twice the current. A year or so
ago.. I
was pushing LEDS to see how much light I could get out. Once I
got
above the rated current I wasn't getting that much more
light...Certainly not double for double the current.
This was a DC measurement and not pulsed. When cranked up to
50mA, I
found a lot more 1/f noise in the LED light output. And if
left at
50mA for several minutes there a slow decay in the total amount
of
light.

George H.

Thanks, that's a new one for me. I'm on a really tight schedule
here. I'll try to find time to run a test tomorrow to compare
brightnesses at 30mA and 60mA.

 

[John S]

I wonder if you've not been to India


NT

I haven't been anywhere that requires more than 4 hours on an airplane.
My loss.

John S

 

[Baron]

[email protected] Inscribed thus:

I believe light output decreases with increase in temperature.

I agree That is why I suggested the longer "off" period.

 

[ehsjr]

John S wrote:

You will be better off to ignore him and continue business as usual.

You might consider taking your own advice. The baiting grows tiresome.

 

[John S]

John S wrote:



You might consider taking your own advice.

You are correct. I might.

The baiting grows tiresome.

Try to not read them.

 

[MrTallyman]

You are correct. I might.


Try to not read them.

What a sad crew. Shame the word crew even gets to be used on you
dopes. Jr used to keep his mouth shut. Looks like even he has jumped
onto the retards without a clue bandwagon.

 

[josephkk]

I wonder how may angels could dance on his head?

None it is way too small. A decent approximation of a geometric point.
(far smaller than a gluon, <10^-99 m)

?-)

 

[Guest]

If I were to use a group of LEDs as described below -

LED type = ordinary 5mm red diffused TH. No data but assumed to
be ~20 mA.
Several LEDs from the batch used for a few years as indicators at
a few mAs. None has failed.
Mounting: 81 LEDs evenly distributed (9x9) on 4.5"x4.5" PCB
Environment: Outdoors, LEDs unenclosed, direct free air, shaded
from direct sunlight, Ta <30 deg C

Current = 60 mA peak at 2Hz, 50% duty cycle
One flashing session = 4 sec, 8 flashes
Session frequency irregular, roughly every 2-10 minutes
To be used for two days at ~6 hrs/day

The arrangement is for temporary emergency use, to be
dismantled/discarded after the said two days. What are the odds
of all LEDs surviving to the end? Informed opinions please.

A while ago, we used some Nichia white 3mm LEDs in a product, driven
from a programmable current source.

Unfortunately the current source design was such that, when the set
point was over ~80% of full-scale, the driver would latch-up and connect
the LED directly across the supply rails (there was a small current-
sense resistor in series, 10R IIRC). The duty cycle sounds similar to
your application, pulsed on and off with a period of about 5 seconds.

Current measured in this condition was about 75 mA, abs max for this
part is 30 mA. We had a couple of dozen units in use for several months
before we noticed. Field failures : 2.

If you are able to replace any failed LEDs on the spot, I'd say you
should be OK.

 

[Pimpom]

[email protected]
says...

A while ago, we used some Nichia white 3mm LEDs in a product,
driven
from a programmable current source.

Unfortunately the current source design was such that, when the
set
point was over ~80% of full-scale, the driver would latch-up
and
connect the LED directly across the supply rails (there was a
small
current- sense resistor in series, 10R IIRC). The duty cycle
sounds
similar to your application, pulsed on and off with a period of
about
5 seconds.

Current measured in this condition was about 75 mA, abs max for
this
part is 30 mA. We had a couple of dozen units in use for
several
months before we noticed. Field failures : 2.

If you are able to replace any failed LEDs on the spot, I'd say
you
should be OK.

Thanks, and thanks also to everyone else who posted meaningful
replies. I read them all but didn't have time to reply
individually to each post. We ran trials today and everything's
OK so far. The actual event starts tomorrow. I'll report the
results later.

 

[ehsjr]

What a sad crew. Shame the word crew even gets to be used on you
dopes. Jr used to keep his mouth shut. Looks like even he has jumped
onto the retards without a clue bandwagon.

No. I don't like seeing personal attacks, and I usually stay
quiet because saying so adds nothing and just extends the number
of posts. In this case I (foolishly, probably) had hope that John
might take his own advice and stop his incessant attacks against
you. It seems that, as the author of the advice, John would
understand its validity.

I wouldn't even have replied here for fear of perpetuating the bickering
that goes on, but I feel I owe you the courtesy of a reply. We've had
some discussions over the years, and you have always treated me with
courtesy. I haven't jumped on anyone's bandwagon. I apologize if I gave
that impression.

Ed

 

[MrTallyman]

No. I don't like seeing personal attacks,

Then you should stop talking to the retard "John S", because you
OBVIOUSLY know nothing about his history of ATTACKING ME.

You stupid ****. I attack that old, retarded, senile **** because he
incessantly does so to me, you clueless twit.

So, it simply boils down to the fact that *I* do not like personal
attacks, and *I* respond in kind.

So **** YOU for being so goddamned oblivious that you complacently fail
to notice the abuse I have been getting from his ilk for years here.

So **** you, and the whore you were shat out of, boy. AND your fucking
old man too, JUNIOR!

Open your fucking eyes, asswipe!

 

[MrTallyman]

I haven't jumped on anyone's bandwagon. I apologize if I gave
that impression.

Ed

In that case, I apologize for thinking that you hadn't noticed and for
replying before reading that you had.

So, you got the standard fare that is no fair to anyone. Just ignore
it, as I read the remainder of you post.

 

[John S]

No. I don't like seeing personal attacks, and I usually stay
quiet because saying so adds nothing and just extends the number
of posts. In this case I (foolishly, probably) had hope that John
might take his own advice and stop his incessant attacks against
you. It seems that, as the author of the advice, John would
understand its validity.

I wouldn't even have replied here for fear of perpetuating the bickering
that goes on, but I feel I owe you the courtesy of a reply. We've had
some discussions over the years, and you have always treated me with
courtesy. I haven't jumped on anyone's bandwagon. I apologize if I gave
that impression.

Ed

Way to go, Ed. You just provoked an attack from AlwaysWrong, NymNoNuts,
or, actually, [email protected]

 

[ehsjr]

Way to go, Ed. You just provoked an attack from AlwaysWrong, NymNoNuts,
or, actually, [email protected]

Yes, I did. (Without wishing to. As I mentioned, I feared that posting
might perpetuate bickering.) I can understand his reacting that way when
he hadn't finished reading the post. What is more difficult to
understand is why you advise people to ignore him, yet you do the
opposite and actively seek to provoke him.

Personally, I like the technical discussions best. I'm conservative
when it comes to LED ratings. I usually run them at about 1/2 max or
less. As others have mentioned, you can get some interesting effects
when experimenting with overdriving them, and, depending on how much
overdrive and duty cycle, you can get away with it at least for a
time. I haven't run into an application yet where I needed to
overdrive them. Have you?

Ed

 

[John S]

Yes, I did. (Without wishing to. As I mentioned, I feared that posting
might perpetuate bickering.) I can understand his reacting that way when
he hadn't finished reading the post.

Really? You don't know him at all. He is not normal. He is defective.

What is more difficult to

understand is why you advise people to ignore him, yet you do the
opposite and actively seek to provoke him.

The people he attacks do not deserve those attacks. He does what he does
because he thinks he is the only authority on whatever subject to which
he is responding and considers everyone else well below him. Worse, if
he thinks that the person is even slightly wrong (in his opinion) he
throws tact (sanity?) out the window and debases the poster as if he
were the most stupid person in the world.

You noted that he attacked you before even finishing your post. So did
I. That is how severely he is flawed in this respect.

Ed, you are a nice person. I can tell. I may not stop my posting of the
email address which so bothers him, but that is because most of his
posts in response to the people here which I respect are offensive to
me. Those people have better control of their emotions, but I sometimes
do not. Okay, my flaw. Please put me in your *Plonk* file. It won't hurt
me and may make you feel better.

Personally, I like the technical discussions best. I'm conservative
when it comes to LED ratings. I usually run them at about 1/2 max or
less. As others have mentioned, you can get some interesting effects
when experimenting with overdriving them, and, depending on how much
overdrive and duty cycle, you can get away with it at least for a
time. I haven't run into an application yet where I needed to
overdrive them. Have you?

Ed

Me too, Ed.

I worked for a company that manufactured and sold LED traffic signal
replacements for the incandescents. Did some temperature experiments and
such. My boss did the light measurements.

I did not run into an application requiring overdrive. Our ambient
temperature requirements were stringent enough that we did not consider
overdrive. The temperature inside a traffic signal can get quite high
and influence the light output significantly. I'm sorry that I do not
remember the numbers because that was 10 years ago and I am no longer young.

I had a great deal of fun with the pedestrian count-down timer signals.
You'd be surprised at some of the requirements. I'd tell you about them,
but that was 10 years ago and....

Cheers,
John S

 

[MrTallyman]

Way to go, Ed. You just provoked an attack from AlwaysWrong, NymNoNuts,
or, actually, [email protected]

Yet another reason why YOU are the fucking troll.

Only retarded asswipe trolls go round posting folks' email addresses in
Usenet.

You are that retarded asswipe.

 

[MrTallyman]

What is more difficult to
understand is why you advise people to ignore him, yet you do the
opposite and actively seek to provoke him.

It is because HE is the troll.

HE is the incompetent, senile old bastard who knows nearly nothing
about electronics.

He was more than happy to jump onto the other retarded asswipe's
bandwagon. Their behavior is quite easy to spot. The simple fact that I
*DO* use profanity and do attack them back, raises my profile so others
will typically agree with the retard's attempts to make it appear as if I
am the troll.

Funny how HE is the retarded bastard pulling the attacks, and posting
folks' emails, and pulling any number of other troll behaviors. He loves
to call others "troll" too. Doesn't take much to notice who the real
asshole is.

 

[MrTallyman]

Personally, I like the technical discussions best. I'm conservative
when it comes to LED ratings.

I have run them at high current and have watched them fail, but that is
simply by adding voltage to a flashlight. I made no attempts to sink any
heat generated. That would certainly make them last longer and is
usually just about all the makers do when they "make" a high wattage
version. They make a good thermal circuit in their mechanical design and
the actual LED die is not a whole lot bigger. They will just handle more
continuous current without failing. I am sure they have a lower MTBF
regardless.

I usually run them at about 1/2 max or
less.

Those should last forever.

As others have mentioned, you can get some interesting effects
when experimenting with overdriving them, and, depending on how much
overdrive and duty cycle, you can get away with it at least for a
time. I haven't run into an application yet where I needed to
overdrive them. Have you?

That flashlight worked better than any LED flashlight I have ever seen.
It only worked for a short time though. Good thing it was a 12 LED cheap
$3 Harbor Freight job. I have a few of them. Really good, cheap
platforms for testing out things like overdriving, etc.

Used to make music color lights out of them. Nowadays I use software.
The best in existence is G-Force from Sound Spectrum. It is a plug-in
for Windows Media Player. I like how it lets me place my images in the
background in false color, while it runs fractals and such up front.
It doesn't get any better.

http://www.soundspectrum.com/g-force/index.html?src=home

 

[MrTallyman]

Really? You don't know him at all.

ACtually, asswipe... it is YOU who does not know me at all.

Proof that you are a troll is how you act as if you do know me.

He is not normal.

You are unqualified to make any assessment about any human being,
asshole. So none which you make will carry ANY credibility whatsoever.
You could be a bit more retarded, just not in this life.

He is defective.

No, fucktard... YOU are defective. Your behavior in this thread alone
proves it. There are hundreds of other examples. This is an electronics
group, troll. Why don't you try that? Oh... that's right... you do not
know a goddamned thing about electronics.