Multcolored LED Light Diffusing

[MrAl]

Hello,


I purchased some 5mm 20ma tri color LED's, red, green, and blue. I had one already but it was a higher power device. With the higher power device i noticed that the colors do not 'mix' well because the lens was water clear. They make these LED's with three different color LED's internally, the red green and blue, and unfortunately that means they are spaced apart inside the LED. That spacing means that the light comes out of the LED at different angles and does not mix well.
The smaller ones (the 20ma ones) have a different epoxy in that it is not water clear but is foggy white which diffuses the light and makes at least some attempt to properly 'mix' the three different colors. Mixing properly would mean we could get any color of the rainbow: yellow, violet, orange, etc., as well as the three primary colors.
The problem is that even with a foggy lens the colors do not mix very well. You can see blue coming out mostly on one side (and toward the front) and red coming out the other side and green out at a different angle, more or less. You can see some mixing but not much. The result is that the colors look independent not one continuous color like yellow for example.
If i hold a piece of foam packing material (not the regular foam although that may work too) i get much better mixing. The color appears to be consistent and much more even. However, this foam is 1/4 inch thick and not very stable physically.

I was hoping others ran into this too and have some other ideas for diffusing the light.

The LED's as they are make nice indicators without a diffuser, as you can light up the red, green, and blue to indicate different modes of operation for your application. However, i would also like to get the in between colors like yellow, orange, violet, etc., which requires mixing two or more colors and that requires some sort of diffuser.

Any ideas would be appreciated.

 

[ronv]

I'm searching around the house for some type of plastic with some tiny bumps on it. No luck yet.

 

[Mickster]

Hi MrAl,
do you have any of that Polymorph/Shapelock plastic left?
You could try making a light-pipe with it and use that for the indication, instead of mounting the LED directly on the enclosure.

 

[4pyros]

You can sand the LEDs or put hot glue on them, and try sticking them in ping pong balls.

 

[4pyros]

Scotch Tape works all so.

 

[alec_t]

Or you could mount the LEDs in a mirror-box with a small viewing window.

 

[MrAl]

Hi,

Some very good ideas thanks much.


Mickster:
Oh yeah, geeze, i forgot i had that stuff ha ha. Lucky you remembered
That stuff will work pretty well i think because it naturally diffuses the light, and it
is white (neutral) color so i think it wont bother the tint.
It gets funny looking if handled a lot, but this will just be an indicator so i think it's ok.

4pyros:
I tried sanding other LED's but what happens is the diffuse volume isnt large enough to
actually 'diffuse' the the light, instead it acts like a projector screen showing whatever
light that happens to hit it. That means we still see red, green, blue in different areas
of the epoxy.
Hot glue sounds very good too. I like that stuff anyway and it's easy to use. I'll try that
along with the polymorph.
Pink pong ball does sound interesting although i dont think i want it that big.
Not sure if i have any of that Scotch tape that you can write on, i think that is what
you mean, but maybe i could get some. I guess you mean layers of tape.

alec:
Mirror box? You mean a box with mirros on all 6 sides internally?


All:
I do have lots of hot glue and polymorph so i'll probably try that first.
Hot glue is fast enough, and polymorph about the same time to heat up water to soften it.
This has to hold up over time too, so it cant be too shabby.

 

[4pyros]

MrAl; Ping Pong balls are made out of the same stuff they use to defuse the square push buttons. Just cut some up.
Yes the wright on Scotch Tape, its about the same stuff, but yes you need a few layers. I used it to defuse some LED Christmas lights that I was using on mini trees. I taped red,green,blue, and white together. It made a nice violet color when viewed from 10 or so feet away.

 

[alec_t]

alec: Mirror box? You mean a box with mirros on all 6 sides internally?

Yes. Aluminium foil would do as the 'mirrors'. Slightly crumpled foil would randomise the light reflections to improve the colour blend.

 

[eTech]

Hmm..

How about buying a diffuser cap?
Or, maybe sanding the led plastic lense?

eT

 

[MrAl]

Hello again,


4pyros:
Oh so you meant just use a part of the ping pong ball, that makes sense. The whole thing would be kinda big

alec:
Yes that sounds reasonable. As long as it does not come out too big i dont mind. I want it small like the LED itself, which is the 5mm type.

eTech:
Diffuser cap?
Sanding the LED itself does not work that well because after sanding the *volume* of material that acts as a diffuser is not 'thick' enough to properly diffuse the light, so it acts more like a projection screen where the light is projected onto the surface, but it only diffuses ever so slightly not enough to make a difference.
To make sanding work, i'd have to sand the surface, coat with clear paint, sand that, coat with clear paint, sand that, etc., etc., until i was able to build up a thick layer of 'foggy' material. So the layer of diffusing material has to be somewhat thick.
Also be aware that the lens is already a foggy type lens not a water clear, and even that is not enough.

 

[Mickster]

Hello again,
Sanding the LED itself does not work that well because after sanding the *volume* of material that acts as a diffuser is not 'thick' enough to properly diffuse the light, so it acts more like a projection screen where the light is projected onto the surface, but it only diffuses ever so slightly not enough to make a difference.
To make sanding work, i'd have to sand the surface, coat with clear paint, sand that, coat with clear paint, sand that, etc., etc., until i was able to build up a thick layer of 'foggy' material. So the layer of diffusing material has to be somewhat thick.
Also be aware that the lens is already a foggy type lens not a water clear, and even that is not enough.

As far as I see it, the only reason for there being the large amount of material above the dies, is to meet the T1 3/4 package specs, in order to fit mounting fixtures etc.
There would be nothing to stop you from cutting off roughly the top half of the package height and replacing it with some epoxy, hot glue, plastic, or some other form of diffusing material.
If you even wanted to meet the T1 3/4 specs again, you could make a mold and pour your diffuser material in, then insert the cut down LED.
Another thought could be to alter the surface of the LED where it has been cut, say using a ball-shaped Dremel tool to make an indent, changing the angle of incidence, to bounce the beam from the dies around even more.
I haven't tried the above, but it may possibly work for your needs.

Regards.

 

[eTech]

eTech:
Diffuser cap?

yeah...diffuser cap. Its a small cover that fits over the lens to help diffuse the light. I've used them for T1 3/4 incandesent bulbs years ago. White LEDs didn't exist then. The caps are still available. I'm assuming it will work on an LED.

eT

 

[MrAl]

Hi again,

Mickster:
Yeah i'll have to start trying some of this stuff. I also remembered that hot glue yellows over time so i have to consider that too.

eTech:
Well then i'll have to look for some of those caps to try that. Where did you find yours?

 

[4pyros]

Mickster:
Yeah i'll have to start trying some of this stuff. I also remembered that hot glue yellows over time so i have to consider that too.

Get the UV stabilized glue meant for outdoors, not the cheap stuff.

 

[MrAl]

Hi 4pyros,

Where did you find this glue? I'll check it out, thanks.

 

[4pyros]

Hi 4pyros,

Where did you find this glue? I'll check it out, thanks.

Start here;
**broken link removed**

 

[atferrari]

You can sand the LEDs or put hot glue on them, and try sticking them in ping pong balls.

A common but bulky solution for small ones.

 

[atferrari]

A solution I occasionally used was a small cap made of the paper used to wrap pieces of expensive crockery. Problem is that luminosity will be reduced. (As far as I know, difusion entails reduction always...)

 

[MrAl]

Start here;
**broken link removed**

Hi,

I ran into that AdTech for hot glue but when i went to the site they seem to only sell in bulk and it is not perfectly clear which one of the many they have is the right formula. Perhaps you can take a look too.