Blue LEDs? when did that happen?

G

guy-jin

Guest
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?
 
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?
Click to expand...
Must have been an old book, the problem was allways getting the right material
to make them, now we have UV leds as well. The Xray led is still a way offf yet
though.
 
"guy-jin" <guyvf@usa.net> wrote in message
news:774e24ad.0409281409.260b5f16@posting.google.com...
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?
Click to expand...
By one man Shuji Nakamura

http://www.businessweek.com/1999/99_24/b3633068.htm

Adam
 
Austin,

Many things have changed since you were frozen in the 60's. And yes,
Liberace was gay.

Bob

"guy-jin" <guyvf@usa.net> wrote in message
news:774e24ad.0409281409.260b5f16@posting.google.com...
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?
Click to expand...
 
On Wed, 29 Sep 2004 00:19:48 +0100, "Adam Aglionby"
<nws@capersville.co.uk> wrote:

"guy-jin" <guyvf@usa.net> wrote in message
news:774e24ad.0409281409.260b5f16@posting.google.com...
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?
Click to expand...
It's the semiconductor bandgap, not the physical dimensions, that
determines the color.

By one man Shuji Nakamura

http://www.businessweek.com/1999/99_24/b3633068.htm

Adam
Click to expand...
I think the Cree SiC blue led's predated these, but they were
horrendously inefficient: they needed something like 3 volts, 50 mA to
be a decent panel indicator. Paralleled 74S38s + 27 ohms from 5 volts!

But where do they use blue traffic lights?

John
 
John Larkin wrote...
Adam Aglionby <nws@capersville.co.uk> wrote:

guy-jin wrote ...
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?

It's the semiconductor bandgap, not the physical dimensions, that
determines the color.

By one man Shuji Nakamura
http://www.businessweek.com/1999/99_24/b3633068.htm

I think the Cree SiC blue led's predated these, but they were
horrendously inefficient: they needed something like 3 volts, 50 mA to
be a decent panel indicator. Paralleled 74S38s + 27 ohms from 5 volts!
Click to expand...
The modern high-efficiency blue (and white) LEDs also require 3V, as
determined by the band-gap voltage like you said. But they give more
light at lower currents. These days all the rage is purple LEDs, for
a much much more impressive light-color sensation.

But where do they use blue traffic lights?
Click to expand...
Isn't purple needed for low-rider under-the-car lighting?


--
Thanks,
- Win

(email: use hill_at_rowland-dotties-org for now)
 
Winfield Hill wrote:
John Larkin wrote...

Adam Aglionby <nws@capersville.co.uk> wrote:

guy-jin wrote ...
I ran across an old electronics book, the beginning chapters of
which deal with light emitting diodes. it described the problem of
blue LEDs; IIRC, the distance between the poles determines the
color, but when you get them far enough apart to make blue light,
current no longer flows between the poles.

Am I remembering correctly, and how was the problem solved?

It's the semiconductor bandgap, not the physical dimensions, that
determines the color.

By one man Shuji Nakamura
http://www.businessweek.com/1999/99_24/b3633068.htm

I think the Cree SiC blue led's predated these, but they were
horrendously inefficient: they needed something like 3 volts, 50 mA
to be a decent panel indicator. Paralleled 74S38s + 27 ohms from 5
volts!

The modern high-efficiency blue (and white) LEDs also require 3V, as
determined by the band-gap voltage like you said. But they give more
light at lower currents. These days all the rage is purple LEDs, for
a much much more impressive light-color sensation.

But where do they use blue traffic lights?
Click to expand...
Japan, I think!
 
On 28 Sep 2004 19:51:47 -0700, Winfield Hill
<Winfield_member@newsguy.com> wrote:

John Larkin wrote...

Adam Aglionby <nws@capersville.co.uk> wrote:

guy-jin wrote ...
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?

It's the semiconductor bandgap, not the physical dimensions, that
determines the color.

By one man Shuji Nakamura
http://www.businessweek.com/1999/99_24/b3633068.htm

I think the Cree SiC blue led's predated these, but they were
horrendously inefficient: they needed something like 3 volts, 50 mA to
be a decent panel indicator. Paralleled 74S38s + 27 ohms from 5 volts!

The modern high-efficiency blue (and white) LEDs also require 3V, as
determined by the band-gap voltage like you said. But they give more
light at lower currents. These days all the rage is purple LEDs, for
a much much more impressive light-color sensation.
Click to expand...
Every couple of years we have to write ECOs to change the
current-limit resistors on a lot of our products that use blue LEDs.
They keep getting more efficient, and customers complain that our
front-panel lights are blinding them. We must average about 5 mA these
days, down from 50 with the old Cree parts.

John
 
In article <jq7kl0tn106j1cgllt87f1tkgrlpubmekp@4ax.com>,
John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote:

On Wed, 29 Sep 2004 00:19:48 +0100, "Adam Aglionby"
nws@capersville.co.uk> wrote:


"guy-jin" <guyvf@usa.net> wrote in message
news:774e24ad.0409281409.260b5f16@posting.google.com...
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?

It's the semiconductor bandgap, not the physical dimensions, that
determines the color.


By one man Shuji Nakamura

http://www.businessweek.com/1999/99_24/b3633068.htm

Adam



I think the Cree SiC blue led's predated these, but they were
horrendously inefficient: they needed something like 3 volts, 50 mA to
be a decent panel indicator. Paralleled 74S38s + 27 ohms from 5 volts!

But where do they use blue traffic lights?

John
Click to expand...
Blue plus yellow equals green...

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See <http://www.sonic.net/~dakidd/main/contact.html> for full details.
 
"Bullwinkle Jones" <bullwinklejones@gmail.com> wrote in message news:<H5q6d.590$eq.23@edtnps84>...

But where do they use blue traffic lights?

Japan, I think!
Click to expand...
Not that I ever saw.
 
On Wed, 29 Sep 2004 05:38:23 GMT, Don Bruder <dakidd@sonic.net> wrote:

In article <jq7kl0tn106j1cgllt87f1tkgrlpubmekp@4ax.com>,
John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote:

On Wed, 29 Sep 2004 00:19:48 +0100, "Adam Aglionby"
nws@capersville.co.uk> wrote:


"guy-jin" <guyvf@usa.net> wrote in message
news:774e24ad.0409281409.260b5f16@posting.google.com...
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?

It's the semiconductor bandgap, not the physical dimensions, that
determines the color.


By one man Shuji Nakamura

http://www.businessweek.com/1999/99_24/b3633068.htm

Adam



I think the Cree SiC blue led's predated these, but they were
horrendously inefficient: they needed something like 3 volts, 50 mA to
be a decent panel indicator. Paralleled 74S38s + 27 ohms from 5 volts!

But where do they use blue traffic lights?

John


Blue plus yellow equals green...
Click to expand...

Is that somehow better than using green?

John
 
In article <t3lll09ka452jvpb3h8aj503pkpe3fr3ca@4ax.com>,
John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote:

On Wed, 29 Sep 2004 05:38:23 GMT, Don Bruder <dakidd@sonic.net> wrote:

In article <jq7kl0tn106j1cgllt87f1tkgrlpubmekp@4ax.com>,
John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote:

On Wed, 29 Sep 2004 00:19:48 +0100, "Adam Aglionby"
nws@capersville.co.uk> wrote:


"guy-jin" <guyvf@usa.net> wrote in message
news:774e24ad.0409281409.260b5f16@posting.google.com...
I ran across an old electronics book, the beginning chapters of which
deal with light emitting diodes. it described the problem of blue
LEDs; IIRC, the distance between the poles determines the color, but
when you get them far enough apart to make blue light, current no
longer flows between the poles.

Am I remembering correctly, and how was the problem solved?

It's the semiconductor bandgap, not the physical dimensions, that
determines the color.


By one man Shuji Nakamura

http://www.businessweek.com/1999/99_24/b3633068.htm

Adam



I think the Cree SiC blue led's predated these, but they were
horrendously inefficient: they needed something like 3 volts, 50 mA to
be a decent panel indicator. Paralleled 74S38s + 27 ohms from 5 volts!

But where do they use blue traffic lights?

John


Blue plus yellow equals green...


Is that somehow better than using green?
Click to expand...
Doubtful that it's "better", but... <shrug>

(And never mind the fact that I brain-farted on the fact that we've had
green LEDs seemingly forever - Was thinking in terms of "Damn... Only
have red and yellow - Gotta "build" green if using LEDs, and the only
way to do that is yellow plus blue.")

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See <http://www.sonic.net/~dakidd/main/contact.html> for full details.
 
In article <slrnclmvso.4j9.don@manx.misty.com>,
don@manx.misty.com (Don Klipstein) wrote:

In article <izF6d.15638$54.238587@typhoon.sonic.net>, Don Bruder wrote:

Doubtful that it's "better", but... <shrug

(And never mind the fact that I brain-farted on the fact that we've had
green LEDs seemingly forever - Was thinking in terms of "Damn... Only
have red and yellow - Gotta "build" green if using LEDs, and the only
way to do that is yellow plus blue.")

Ever mix the light from a blue LED with the light from a yellow one?
It's certainly not green.
Click to expand...
Can't say I have. To be honest, I don't think I recall ever even having
a blue and a green LED in the same room together, let alone trying to
mix 'em.

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See <http://www.sonic.net/~dakidd/main/contact.html> for full details.
 
I once had some LEDs which gave all the colours of the rainbow including
xray, I put them directly across the mains, WOW!!! I lost my cat the same
night.

Gordon.
-----------------------------------------------------------------------------------------


"Don Bruder" <dakidd@sonic.net> wrote in message
news:j7O6d.15702$54.239606@typhoon.sonic.net...
In article <slrnclmvso.4j9.don@manx.misty.com>,
don@manx.misty.com (Don Klipstein) wrote:

In article <izF6d.15638$54.238587@typhoon.sonic.net>, Don Bruder wrote:

Doubtful that it's "better", but... <shrug

(And never mind the fact that I brain-farted on the fact that we've had
green LEDs seemingly forever - Was thinking in terms of "Damn... Only
have red and yellow - Gotta "build" green if using LEDs, and the only
way to do that is yellow plus blue.")

Ever mix the light from a blue LED with the light from a yellow one?
It's certainly not green.

Can't say I have. To be honest, I don't think I recall ever even having
a blue and a green LED in the same room together, let alone trying to
mix 'em.

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21,
2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in
the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See <http://www.sonic.net/~dakidd/main/contact.html> for full details.
Click to expand...
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top