Re: [Phys-l] LED phosphorescence

[Spinozalens@aol.com]

In a message dated 6/25/2011 5:50:15 A.M. Eastern Daylight Time,  
Spinozalens@aol.com writes:


In a  message dated 6/25/2011 1:03:36 A.M. Eastern Daylight Time,   
jim.deane@gmail.com writes:

A  more cost effective method is  to use UV or blue LEDs and
>  broaden  the light spectrum  using phosphors.
>
> What I am pretty sure is  happening is  that the phosphor needs  time to 
heat
> up before it   emits light over a broad spectrum, the purple tinge  
reflects
>  the  fact that the LED's being used are emitting UV light. I can't   find
> anything in the literature on LED lighting that talks about   this, hence 
my  post.
> Bob Zannelli

I am  curious,  when you cut power to the LED array, does the array
continue  to glow at  all?  If so, what color?

It won't be a  long-acting phosphor like  they use in commercial
glow-in-the-dark  materials these days, but it may  have a residual
glow.

--  





When the LED lights are shut off , they go dark  instantly. If they have 
been on  
recently, and have not had time to  cool down ,  they come to full 
brightness  
instantly. So it's  definitely heat related. There is nothing available 
that  
explains  this effect that I can find. But it has to be a temperature 
effect  
with  the phosphor material. LEDs switch at high speed , they are  used in 
fiber optic  communication. ( Though LASERS are better.)  


Bob Zannelli