Need the magic formula!!

[Govmnt_Lacky]

So I am using diffused RGB LEDs and I cannot get a good yellow color out of it!

Diffused are supposed to help with color blending but, no matter what CLR values I use for the Red and Green legs, I simply cannot get a Yellow color out of the darn thing! All I see is a Green/Red mess. NOT Yellow!

Does anyone have the magic CLR value formula to get a good Yellow out of this thing??

Thanks

[Kipper4]

I dont have any answers but it sure made me giggle. Thanks

[wavley]

Here is the formula

[R.G.]

Try rotating the LED about its long axis at something over 60 rps/3600rpm to blend the light better by the human eye's persistance of vision.

[lungdart]

RGB LEDs can notoriously not blend well. Try using RGBW LEDs instead. The extra white help with colour mixing.

Another alternative of course is to diffuse the light further. A little hot glue perhaps?

[armdnrdy]

The Infinite Flanger uses a "tri color" 3 lead red/green LED......and it works well. (the third color is more of an orange than yellow, but definitely discernible from the red or green)

Take a look at the circuit to see if there is some clue to it's tricolor goodness!

[MrStab]

Another alternative of course is to diffuse the light further.

i was just about to say - i'm pretty sure i read a similar thread on here a while back where diffusion was the recommended fix. i like RG's idea, though - if you get a bunch of em you could have a pedal and a DIY TV to watch on stage!

[johngreene]

Are you looking at the color of the LED itself or the color of the light it is emitting? The LED itself will aways show a mix of colors, but if you put them in an array and have them all emitting the same it will look much more yellow, at a distance.
I worked on the design of the pixel for this product:

http://www.youtube.com/watch?v=6-037acrKxI

If you notice at 1:35, in the close up the lettering looks greenish but in the next shot at a distance it looks a lot more yellow.

[lungdart]

The Infinite Flanger uses a "tri color" 3 lead red/green LED......and it works well. (the third color is more of an orange than yellow, but definitely discernible from the red or green)

Take a look at the circuit to see if there is some clue to it's tricolor goodness!

Hmm, that is a good point about the bi-colours. I have used them in the past and had good success mixing the colours. But with RGB's they just don't get the same diffusion.

[Govmnt_Lacky]

Ok....

Things I know:

- These RGB LEDs can be used to make every color with a PIC.

Things I don't know:

- How to make the color Yellow without a PIC

I know the capability is there. I just don't know the magic values to do it 

[johngreene]

Ok....

Things I know:

- These RGB LEDs can be used to make every color with a PIC.

Things I don't know:

- How to make the color Yellow without a PIC

I know the capability is there. I just don't know the magic values to do it 

Equal amounts of red and green will yield yellow. Equal current through the red and green LED will give you yellow IF it is the right color of red and green and IF the red and green LEDs are equal in luminescent intensity.
http://www.rapidtables.com/web/color/RGB_Color.htm
http://www.theledlight.com/img-RGB/rgbColorChangingLEDLights.jpg

--john

[armdnrdy]

Here's a youtube video.

http://www.youtube.com/watch?v=qDajSADjTX4

Get past the real entertaining part (watching him breadboard the circuit) and you'll see yellow achieved by powering the red and the green.

[stallik]

Agreed, equal current to each colour does not necessarily make for equal brightness and the colour fidelity will be limited by design. Equal red and green will only make pure yellow if they are themselves pure and they are visually diffused together via a diffusing plate, distance or blur.
If you accept these limitations but are unhappy with the visual appearance of one colour combination then a possible solution might be to replace  the led resistors with a pot or trimmer and fiddle with the settings till you are happy with the colour at your required viewing distance. Then replace the trimmers with resistors of the same value.
The formula would therefore be
Y=5uk1t n C

[pappasmurfsharem]

Can you not hook up a minimum CLR to each then two pots in series and just dial it in?

[deadastronaut]

i'm with kevin on this...use magic trimmers.

ive never used rgb leds but they look like fun...

[samhay]

Y=5uk1t n C

This made my morning.

[PRR]

> RGB LEDs can be used to make every color

Well, no.

Three single (narrowband) colors can not make an arbitrary color.

Three single colors can "often" "fool the eye" into seeing the in-between colors.

It works pretty-good in color film and TV. However the dyes and phosphors are not the LED-preferred colors; rather chosen for best eye effect on typical scenes. Yes, there are now LED TVs and I do not know what colors they use, if they may be different than the colors of the 3-color jellybeans or have been tweaked to "fool the eye on typical scenes".

There may be a plot in the data showing what parts of the eye's color-gambit these LEDs will cover "tolerably well".

http://en.wikipedia.org/wiki/Gamut

I think John is pointing-out that the color you "see" is highly dependent on the other colors around it. I think an incandescent lamp is "white", but if I take it in sunlight it is pretty red. A single dot in a dark room is a poor reference.