Rant. Well, semi-rant.
How come they're not really white, but a really, really light blue? Are there LEDs that *ARE* white? Like, a WARMER white?
I keep hoping a warmer white comes out, but nooo.. just brighter blue-whites. Hmph.
Me.
Posted by: Roger
Re: White LEDS.. - 29/01/2004 03:20
IIRC, they're not really white. They're generally a blue/UV LED with a flourescent coating.
Hence the blue tinge.
Posted by: Skunk
Re: White LEDS.. - 29/01/2004 09:50
I heard white is the hardest color to produce in LEDs.
Is this true?
Posted by: mtempsch
Re: White LEDS.. - 29/01/2004 12:11
Yup - because white is a mix of all colors, while a LED typically emits light heavily centered around a specific color/wavelength...
I've seen pretty decent white (not high-intensity though) from RGB LEDs (LEDs with 3 (or more) diodes internally, one each red, green, blue), but it required some finetuning of the voltages to each element...
One can also do pretty neat effects with independent slowly changing voltage on each of the inputs...
/Michael
Posted by: g_attrill
Re: White LEDS.. - 29/01/2004 12:27
One can also do pretty neat effects with independent slowly changing voltage on each of the inputs...
For christmas my mum got a frosted 3D-star decoration which cycled through lots of colours - I inspected it and it looked like it was a single RGB LED doing what you describe - looked very nice.
Gareth
Posted by: peter
Re: White LEDS.. - 29/01/2004 12:37
Yup - because white is a mix of all colors, while a LED typically emits light heavily centered around a specific color/wavelength...
As a result of one of those pub conversations that started with "Show me something macroscopic that demonstrates that quantum mechanics is real", it turns out that you can predict the colour of an LED from its voltage drop, or vice versa, with complete accuracy by converting eV to joules for the incoming electrons and using E=hf for outgoing photons, on the quantum-mechanical basis that each electron's energy is released in exactly one photon.
Peter
Posted by: siberia37
Re: White LEDS.. - 29/01/2004 13:24
I've seen some pretty good and very bright white leds that my father in law has. He works for a sign company and they use them to replace white neon in signs- so they are bright and don't have a noticeable color tint. They are not cheap though- if you need more info on where he gets them let me know.
As a result of one of those pub conversations that started with...
I dunno what pub YOU go to, but they sound pretty up-tight.
Me.
Interesting! Thanks! Now I need them to give light out in ALL directions, and then.. THEN! I'll have PERMANENT REPLACEMENTS for all the little bulbs in my Pinball Game!
Muahaha!
*ahem*
Sorry.
Me.
Posted by: Roger
Re: White LEDS.. - 29/01/2004 16:27
I dunno what pub YOU go to
IIRC, that conversation was started in the Live and Let Live in Cambridge, just off Mill Road. We did the working out on the whiteboard in the office the following morning -- 'cos none of us could remember any of the constants.
Posted by: Mach
Re: White LEDS.. - 09/03/2004 06:40
I just received this in my inbox. Thought you might be interested.
We proudly present a series of brand new white LEDs
WHITE LEDs based on ZnSe technology. These ZnSe LEDs emit white light without blue LED conversion YAG!
how it works:
ZnSe LED chips emitting two colors at the same time, one peak at 484 nm (blue) and one peak at 605 nm (yellow) - mixing these two wavelengths inside the epoxy housing "generates" white light:
http://www.roithner-laser.com/
http://www.roithner-laser.com/All_Datasheets/Pricelists/
Hmm.. Interesting. I'm mwilling to try that.. Thanks!
Mike.