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Understanding RGB Controllers and Tri Colour LED's

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RodneyB

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I am trying to get an understanding of how A tri Colour LED works.



The attached circuit is part of a circuit I built and have seen no benifit.



By usig three out put from either a PIC or a 4029 IC switching on the diffarent colours should you get a mix of light?



I thought that the capacitor on the base of the transistor was going to fade the colours in and out but have no idea or understanding how.



I also want to know if there is a way of getting the colour to evenly distribute under a transparent surface. I have mounted my circuit on a mirror and behind some white plastic. I thought I would get a mix of colour. All I get is a very distinct dot fading off of a single colour.
 

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If more than one LED is active at a time then you do get a mix of light if the LEDs are far enough away from your eye so that the subtended angle is small. Too close and you will see the individual colours.
You could try translucent polythene sheet (e.g. from a milk bottle), with its surface abraded by glasspaper, as a diffuser.
 
get rid of the capacitor, and maybe even the transistor. Unless it's a very high current LED, the PIC should be able to drive it directly. Use pulse width modulation (varying on and off times) to fade the color in and out. Also, go to the Windows paint program, call up the color pallette, do custom color, and look at how a mix of the three base colors (red, green, blue) mix to yield different colors. Use max value as 100%, and vary %'s of all three to get different colors. Red and green (in equal parts) will yield yellow, etc... however, you have to understand your LED... does the Red/green/blue LEDs all have the same milicandella values for a given drive current? you may have to play games to even them out. When we did a power supply board for Sharp LCD displays, the red/grn/blu inputs had adjustments to even out the colors for a given drive level. You may have to do that on the resistors to the LED to get a match of brightness per on time. Like a bicolor led, red/grn, both on should yield yellow, but if you drive both LEDs the same, you get reddish/orange, as the red LEDs are brighter than the green LEDs.
 
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I also want to know if there is a way of getting the colour to evenly distribute under a transparent surface. I have mounted my circuit on a mirror and behind some white plastic. I thought I would get a mix of colour. All I get is a very distinct dot fading off of a single colour.

If the LED is a 5mm type with a clear lens and normal LED shape, the rounded end (lens) of the LED will focus the 3 internal chip lights in 3 skinny beams in 3 different directions. So with all 3 RGB chips lit up, it will send out 3 different coloured beams of light in 3 slightly different directions.

I've had some success with grinding the top of the LED flat, to completely get rid of the curved part. Then the 3 internal chips will send out light in a much broader angle and cover each other's spread much better.

Then for a diffuser you can use a layer or two of some rippled clear plastic, like the bumpy glass stuff they make bathroom windows out of. Some food containers have a rippled but clear surface. Remember to put some distance between the LEDs and the rippled plastic, and between layers of the rippled plastic. Overall it breaks up the light directions from the 3 chips and mixes them up.

It's also better if you have multiple RGB LEDs, and not just one. :)
 
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