White LED spectrum?

[Paul Conners]

Would like to find white SMD LEDs suitable for use as backlight for LCD
monitors where the CCFL lamps have burned out. So need is for consistency
between units and... well, "whiteness". ;-)

Or other parameters I should be considering?

Any recommendations (ie, LEDs you think would be good for this)?

(And yes, I can Google and have.)

Thanks,
Dave

[spamtrap1888]

While we're at it I'd like a digital "film back" for my Nikon 35 mm
camera.

[Dennis]

"spamtrap1888" <spamtr...@gmail.com> wrote in message
news:9bb7dae8-b77f-449f...@v8g2000pro.googlegroups.com...

===============================

Can you get them?

[Jeff Liebermann]

On Fri, 14 Oct 2011 14:49:43 -0700, Paul Conners
<pconn...@gUSmail.com> wrote:

>Would like to find white SMD LEDs suitable for use as backlight for LCD
>monitors where the CCFL lamps have burned out. So need is for consistency
>between units and... well, "whiteness". ;-)

I'm going to be doing this in about a week when the parts arrive.
<http://www.lcdparts.net/howto/LEDBACKLIGHT_MOUNT.aspx>
<http://www.lcdparts.net/panelledkit.aspx>
<http://www.lcdparts.net/LB.aspx>
<http://www.lcdparts.net/UB.aspx>
<http://www.lcdparts.net/XB.aspx>
<http://www.lcdparts.net/panelledkit.aspx>
<http://www.instructables.com/id/LED-Backlight-for-Your-LCD-Monitor-or-Television/>
Plenty more found with Google.

>Or other parameters I should be considering?

You should consider disclosing the maker and model of LCD monitor
you're modifying.

You're going to have problems with getting consistent white. The
color will NOT be the same as CCFL, but close enough to be useful. The
better LCD backlit TV's use individual colored LED's, with a optical
filter/phototransistor combination to adjust the intensity of each
until it looks white. What happens is that different color LED's fade
at different rates. Without feedback, the backlighting would slowly
turn red/orange.

>Any recommendations (ie, LEDs you think would be good for this)?

Nope. No maker and model number, no specifics.

>(And yes, I can Google and have.)

The key words are "led strip light" and "CCFL replacement".

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com je...@cruzio.com
# http://www.LearnByDestroying.com AE6KS

[N_Cook]

Paul Conners <pconn...@gUSmail.com> wrote in message
news:0001HW.CABDFC87...@news.eternal-september.org...

I take it you will replace the 2mm or so diameter CCFL with a line of LEDs .
The tube is uniform illumination along its length, how will you avoid
stripiness of illumination?
It is very sophisticated dispersion sheets backing the display to make sure
no graduation of illumination across the width of those sheets.

[Salmon Egg]

In article
<0001HW.CABDFC87...@news.eternal-september.org>,

Paul Conners <pconn...@gUSmail.com> wrote:

> Would like to find white SMD LEDs suitable for use as backlight for LCD
> monitors where the CCFL lamps have burned out. So need is for consistency
> between units and... well, "whiteness". ;-)
>

I really have no help for the question asked, but I think people
interested in the subject may have an answer to one of my questions.

I have a relatively new Samsung LCD monitor using LED back lighting.
When the computer is not providing a signal, such as waking from sleep,
I see a speckling or snow rather than steady background light. I have
two competing explanations.

1. The LED light is sufficiently spatially coherent to generate "laser
speckle." For example, you can see colored speckle in your fingernail
when illuminated by the sun. At one time I saw laser speckle from a
noble gas laser providing a mixture of lines that gave white looking
light.

2. With no signal, the noise in the video line was amplified in the
monitor circuitry. The display was presenting this as a fine churning
snow. When the computer finally was sending a signal, the pixels were
either fully on or fully off.

Does anyone have bette insight on this matter than I do?

--

Sam

Conservatives are against Darwinism but for natural selection.
Liberals are for Darwinism but totally against any selection.

[William Sommerwerck]

"White" LEDs are actually blue LEDs with a phosphor that glows yellow under
blue light. The eyes sees blue + yellow = white.

Their spectrum is anything but continuous -- or even peaked at the right
points -- so it's highly unlikely to work.

[Rich Webb]

Most white LEDs are phosphor-based but hardy as bi-chromatic as you make
them sound. The little Cree in my pocket flashlight has the typical
broad peak around 450 nm and valley around 485 but it's quite continuous
down to 650, tailing off at about 670. Very different from the narrow,
discrete lines from a CCFL.

--
Rich Webb Norfolk, VA

[Loonie]

Three cheers for that. I am looking for one for my Canon A1 and for my
Zeiss Ikon. Is there any movement towards these backs?

TIA

[DaveC]

I appreciate your simple and obviously knowledgable answer. It will help me
in my search for the right decision.

Dave

[DaveC]

> Most white LEDs are phosphor-based but hardy as bi-chromatic as you make
> them sound. The little Cree in my pocket flashlight has the typical
> broad peak around 450 nm and valley around 485 but it's quite continuous
> down to 650, tailing off at about 670. Very different from the narrow,
> discrete lines from a CCFL.

[Rich Webb]

Thanks, Rich.

I think the "striping" issue and potential variance between samples will make
for a less-than-satisfying result.

Thanks,
Dave

[DaveC]

> I really have no help for the question asked, but I think people
> interested in the subject may have an answer to one of my questions.

And I have one word for you: HIJACK.

If you don't have an answer to the OP's question, fine. If you have a
question, START YOUR OWN THREAD.