suggestions for higher power white LEDs to testing?

[Eeyore]

Without the battery or LED, three parts. You didn't follow
and I guess we can leave it there, then.

You didn't answer my question.

 

[Eeyore]

Besides the fact that these are kids, Graham

What makes you think kids read Usenet, let alone even know of its
existence ?

Graham

 

[Eeyore]

Don't you mean: "of using"?
Yes

But, in that vein, why would an Allen-Bradley carbon comp resistor
made in 1945 not work now, and perform to spec.?

Or, for that matter, a 2N2222 made a dozen years ago?

If they haven't been stressed in a high temp environment designed for a
specific lifetime like a CFL they probably will be fine. By the way,
when did you find either in a CFL ?


Why is buying new parts bullshit ?

You bought what you could get, and whether they were "new" parts was
the least of your concern.

I was dealing with authorised distributors already at age 16 and buying
parts in quantity to get price breaks. My hobby had already moved to
small scale manufacture.

Graham

 

[Eeyore]

I've often wondered about aging issues.

Most higher power LED manufacturers quote lifetime at 70% of initial
luminosity.

Graham

 

[Jon Kirwan]

What makes you think kids read Usenet, let alone even know of its
existence ?

Hmm?

I'm talking about _personal_ contact here in my local area
with real kids. I wasn't being serious about asking you to
fly out here and help me. My point there was that if you
were here, met the kids and saw the situation on the ground
here, I think you'd follow a lot better.

Jon

 

[Jon Kirwan]

Most higher power LED manufacturers quote lifetime at 70% of initial
luminosity.

Which provides a definition for one point. It doesn't say
much about the different causes and the general picture or
what one might expect in some specific situation.

Jon

 

[Jon Kirwan]

You didn't answer my question.

Then you'll need to ask it better, I suppose.

Jon

 

[Jon Kirwan]

<snip>
BTW do you
want to buy some LEDs - as long as your not fussy on the colour and buy
by the 1000's I know a guy ....
<snip>

If you are still interested in putting us in touch with each
other, feel free to contact me, directly.

Thanks,
Jon

 

[Jon Kirwan]

A colleague used a white LED to replace a flash lamp in a product.
Part number
LXML-PWN1-100.  We are obviously just flashing it, but when he ran it
CW it hurt to look at it.

~$2.50 each in quantities of 100’s  from Future Electronics.

I think we drive it with only 0.3 to 0.5 amps it claims to be able to
handle 0.7 A.

I will take a look.  [Though I'm honestly not looking (yet)
to buy 100 of a single part.]

Jon

Oh, If these might work for you, I could slip you a few in an
envelope. I've got some other white LED's kicking around from a
previous project, but mostly through hole, lower current ones.

Well, if you feel that is okay. I had no problem at $2.50
ea, just the "100's" part of it. If you are willing to sell
a few of them, I'm fine with that.

There's a slush fund here where I put money for the parts/ supplies
that I steal from work, so I can add a few bucks to help out the
education effort.

Or I can send it.

I just sent $50 to the OSA for a Galileoscope project. Students get
to make their own telescope. The $50 covers parts, one is sent to a
school and I got one for myself (and my kids)

Hehe. Is this something akin to the "one laptop per child"
thing, where you buy two and get one?

Jon

 

[Don Klipstein]

Which provides a definition for one point. It doesn't say
much about the different causes and the general picture or
what one might expect in some specific situation.

As it turns out, Lumileds quotes a projected lifetime until fading to
70% of initial luminosity at a specific current and a specific junction
temperature.

For example:

http://www.philipslumileds.com/uploads/17/DS61-pdf

That one claims average of 70% of initial output at 50,000 hours at 1
amp and junction temperature not exceeding 135 degrees C.

I believe this is only a projection, since I doubt many of these have
been made 50,000 or more hours ago as of 8/27/2010.

 

[Ecnerwal]

Which provides a definition for one point. It doesn't say

much about the different causes and the general picture or
what one might expect in some specific situation.

Well, as to specific causes, cooking is a big one. Pay a lot of
attention to cooling, and/or don't run at peak power. While it's nice to
get everything it's got to give, getting the heat out is a big issue
with the high power LEDs, and not getting the heat out is a major cause
of degradation at higher than expected rates.

 

[Jon Kirwan]

Well, as to specific causes, cooking is a big one. Pay a lot of
attention to cooling, and/or don't run at peak power. While it's nice to
get everything it's got to give, getting the heat out is a big issue
with the high power LEDs, and not getting the heat out is a major cause
of degradation at higher than expected rates.

That seems very good advice to remember. I'll keep it very
much in mind.

Thanks,
Jon

 

[Jon Kirwan]

snip


Google up the youtube videos and sites and links
surrounding modding the Logitech G15 and G19
keyboards. They use an open source stage lighting
management program to individually address every
key's LED color and brightness.

Pretty cool keyboards too.

They have a hardware page at:
http://www.g15-mod.com/e_hardw.htm

But it really looks to me like this is a special keyboard
with all the LEDs and drive circuitry already included when
you buy it. I'm not sure what is being modded, except
perhaps some software? I certainly do not see any schematics
there and the web site is ... well, terse.

Jon

 

[Eeyore]

Well, as to specific causes, cooking is a big one. Pay a lot of
attention to cooling, and/or don't run at peak power. While it's nice to
get everything it's got to give, getting the heat out is a big issue
with the high power LEDs, and not getting the heat out is a major cause
of degradation at higher than expected rates.

Absolutely right. As with any semiconductor device, operation at higher
temperatures reduces device life.

These big LEDs cost a lot, so it makes sense to run them as 'hard' as
you can to get value for money. This not only reduces lifetime but
degrades efficiency too.

Graham

 

[Eeyore]

That seems very good advice to remember. I'll keep it very
much in mind.

Check Ebay for LED heatsinks.

Graham

 

[Grant]

Higher than what? Talk about a overly broad, vague statement.

You could fall back on life halved for each 10'C temp rise? Vague, but
I've seen the idea expressed many times over the years.

Besides, we work with stuff that goes pop sometimes for no apparent reason.

Murphy lives! And that magic smoke is difficult to keep in place

Grant.

 

[Grant]

Grant, I've worked in places that the equipment was operated well
below zero. A 10° C increase would have made the equipment perform
better and not affect it's life enough to notice. The record low at
that location was -69°F and on windy winter days it could be below
freezing inside the control room.

Fair enough I don't live where it snows

I've also used equipment that had strip heaters & a thermostat to
maintain a minimum temperature to prevent condensation. That's why i
said it was a vague statement.

Once I worked for AU agents for Tenney environmental test chambers,
had to fix one where Tenney forgot to put in stainless fixings to
survive their own environments. Customer certainly not impressed
with the rusting heater assembly mounts.

Closest I've been to extreme electronics locales, at least it was in
boxes and not the control room

Grant.

 

[Eeyore]

You could fall back on life halved for each 10'C temp rise? Vague, but
I've seen the idea expressed many times over the years.

Besides, we work with stuff that goes pop sometimes for no apparent reason.

Murphy lives! And that magic smoke is difficult to keep in place

Grant.

Respectable manufacturers will provide the relevant data. Junction
temperature will depend greatly on how good the heatsinking is too.

Graham

 

[Eeyore]

You're an idiot, again, as usual.

You're a troll again as usual.