White LED Life
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Posts: 46,084
Re: Messsage 11: No such thing as a stupid question. In a perfect world,
these LED's should never burn out. But since it is not a perfect world, what
I have found in my travels is that any semiconductor junction will fail if
the temperature exceeds its maximum limit. What I have seen in some
industrial circuits as a field service engineer is the LED gets exposed to
overvoltage conditions that persist long enough to create the excess heat.
Therefore the care and feeding of an LED that guarantees long life should
include some form of filtering, regulation or OV protection.
Re: Message 20: Thanks to Bob for his information as well. In Edmonton we
have about 6 intersections using these new LED's as well (you can tell by
just watching the lights change) and to mixed reviews. I actually have made
up some bright LED signal lights for my motorcycle; just have to get them
installed this winter.
Cheers,
Gerry
Message: 11
Date: Sat, 3 Aug 2002 14:27:30 -0500
From: <warlockd@l...>
Subject: RE: Re: WHITE LED's lenght
> How long do those things last?
>
> I might just be stupid, but I heard, or thought I heard those lights
> burn out. If not, how long do they burn out at higher Volts?
Message: 20
Date: Sat, 3 Aug 2002 19:15:28 -0700 (PDT)
From: Pence Bob <bobpence_2000@y...>
Subject: Re: Re: WHITE LED's
Also, as too brightness, they have products that
replace the hundreds of LED's you see in some traffic
lights with no more than a couple dozen.
=====
Regards,
Bob Pence
these LED's should never burn out. But since it is not a perfect world, what
I have found in my travels is that any semiconductor junction will fail if
the temperature exceeds its maximum limit. What I have seen in some
industrial circuits as a field service engineer is the LED gets exposed to
overvoltage conditions that persist long enough to create the excess heat.
Therefore the care and feeding of an LED that guarantees long life should
include some form of filtering, regulation or OV protection.
Re: Message 20: Thanks to Bob for his information as well. In Edmonton we
have about 6 intersections using these new LED's as well (you can tell by
just watching the lights change) and to mixed reviews. I actually have made
up some bright LED signal lights for my motorcycle; just have to get them
installed this winter.
Cheers,
Gerry
Message: 11
Date: Sat, 3 Aug 2002 14:27:30 -0500
From: <warlockd@l...>
Subject: RE: Re: WHITE LED's lenght
> How long do those things last?
>
> I might just be stupid, but I heard, or thought I heard those lights
> burn out. If not, how long do they burn out at higher Volts?
Message: 20
Date: Sat, 3 Aug 2002 19:15:28 -0700 (PDT)
From: Pence Bob <bobpence_2000@y...>
Subject: Re: Re: WHITE LED's
Also, as too brightness, they have products that
replace the hundreds of LED's you see in some traffic
lights with no more than a couple dozen.
=====
Regards,
Bob Pence
Comments
are two methods of constructing these that I know of: 3 chip and
phosphor. I think the 3 chip has fallen out of favor, but the color
chips age differently and that throws the light off which is a major
problem with that type of LED. The phosphor types actually work like a
fluorescent bulb (there are two or three different phosphor techniques
in use). I wonder if the phosphor ages?
My point is that there are other possible failure points in a white LED
that don't exist in a conventional LED.
Al Williams
AWC
* Easy RS-232 Prototyping
http://www.al-williams.com/awce/rs1.htm
>
Original Message
> From: Gerry Shand/Corrinne Bergen [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ghf2gMUmO5J91YEHTzm3OnO-zSwKBWv7wpZvS9a5mX9VsZa7GH127m7fGdYlU-JqCVQjKuJAIA]res@c...[/url
> Sent: Sunday, August 04, 2002 9:45 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Re: White LED Life
>
>
> Re: Messsage 11: No such thing as a stupid question. In a
> perfect world, these LED's should never burn out. But since
> it is not a perfect world, what I have found in my travels is
> that any semiconductor junction will fail if the temperature
> exceeds its maximum limit. What I have seen in some
> industrial circuits as a field service engineer is the LED
> gets exposed to overvoltage conditions that persist long
> enough to create the excess heat. Therefore the care and
> feeding of an LED that guarantees long life should include
> some form of filtering, regulation or OV protection.
>
> Re: Message 20: Thanks to Bob for his information as well. In
> Edmonton we have about 6 intersections using these new LED's
> as well (you can tell by just watching the lights change) and
> to mixed reviews. I actually have made up some bright LED
> signal lights for my motorcycle; just have to get them
> installed this winter.
>
> Cheers,
>
> Gerry
>
> Message: 11
> Date: Sat, 3 Aug 2002 14:27:30 -0500
> From: <warlockd@l...>
> Subject: RE: Re: WHITE LED's lenght
>
> > How long do those things last?
> >
> > I might just be stupid, but I heard, or thought I heard
> those lights
> > burn out. If not, how long do they burn out at higher Volts?
>
> Message: 20
> Date: Sat, 3 Aug 2002 19:15:28 -0700 (PDT)
> From: Pence Bob <bobpence_2000@y...>
> Subject: Re: Re: WHITE LED's
>
> Also, as too brightness, they have products that
> replace the hundreds of LED's you see in some traffic
> lights with no more than a couple dozen.
>
> =====
> Regards,
>
> Bob Pence
>
>
>
>
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seen green LEDs used as strobes for "stopping" the cilia (propulsion
hairs which move in waves) on microscopic pond life. White light would
be better, but I expect these LEDs continue to glow briefly after the
current stops, so they'd be go good as strobes.
John
In message <000f01c23bcc$f1741900$0101010a@darkstar>, Al Williams
<alw@a...> writes
>Actually, I think there is another consideration with white LEDs. There
>are two methods of constructing these that I know of: 3 chip and
>phosphor.
--
John Fletcher