RGB Leds, More than 7 colors.

Hi

Does anyone have info or circuits for getting more than 7 colors from a RGB led?
Also I DO NOT want to use a micro processor/controller!
Maybe PWM or ? I have a circuit that does 7 colors, but I would really like 256 or more.

Thanks all

You just need to vary the current to each of the three LED's, you can do it via PWM (the microcontroller solution) or via three simple variable resistors. But without knowing what you're trying to do makes it difficult to make suggestions.

use a combination of 4017 decade counters to build resistor ladders. three ladders for the led, and then some clock to drive them in a random or programmatic fashion.

micro controller would be lot simpler!

Find a copy of Bill Bowden's 'Fading-Red-Eyes' circuit, uses 2 opamps to create a low frequency triangle wave. Build three of them, all the same, except the LED and limiting resistor (which you will need to match for each color). I used larger capacitors for a longer fade. It looks better than any microcontroller job I've seen or done, although my AVR is pretty good for just an 8 pin chip and RGB LED (no regulator, resistors or capacitors).

Anyway, back to the opamp circuit... The compnent tolerances will give each color a slightly different frequency, but pretty close. Don't think anybody could sit and stare at it long enough to detect any pattern. It's a simple circuit, but gives the best results I've seen. Forget 256 colors, there will be millions.

WalMart sold a Mood Light that used a microcontroller. It jerked 256 times from dim to bright for each colour. Mine uses opamps and its dimming is SMOOTH.

nuttaphong191 said:

Hi
Maybe PWM or ? I have a circuit that does 7 colors, but I would really like 256 or more. Thanks all

Click to expand...

What’s that secret circuit? Does it use an OPAMP? May be it can extend up to more colours. Can you show your circuit diagram?

7 colours:
Three individual colours of red, green and blue.
Red plus green equals yellow.
Green plus blue equals cyan.
Blue plus red equals purple.
Then all three colours together at the correct brightnesses equals white.

I built one once with opamps... but i have to say, it is so very much eisier if you turn the whole thing into your first microcontroller project, i did, made a fish-light and i am very satisfied with the result search google for the op-amps version, or got to http://tobe.nimio.info/led_mood_lamp.php, is the one i built, and recommend. i would reccommend using microcontrollers because they are so usefull once you can program them, use a programmer like FENG3's RCD programmer ( sorry no link). I use it and it works, plus you can use his circuit design. if you dont already make your own PCB (if you're interested) you can do so very easily using a laser printer... NO acetate NO uv light box NO developer or iron on transfers, just read this page (very easy, hey! i do it, by the way) :**broken link removed**

hope some of this helps

Hi Mike,
The schematic of the Tobe Mood Lamp is wrong. There are no current-limiting resistors between the outputs of the microcontroller and the bases of the transistors. People who made it reported that their microcontroller got so hot it stopped! The author posted a revised circuit at Electronics-Lab but used 10k resistors which are way too high. I recommend 680 ohms.

have you seen the most recent schematic? I am not sure, but i think it has been changed. i used the idea, but added a 5v regulator for mains operation (from xfrmer) and everything is working very well, and everything runs cool, ie, i do not experience the issues that you have described. either way, it doesn't matter, there are plenty of circuits out there that will work fine too.

sorry, yes you are right, he used 10k resistors, I did not i chose 1k