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How to create an Usb controlled rgb light that changes colour depending on input from pc?

Im trying to create an led array of 30 leds (10 red, 10 green, 10 blue) that recieve an input from the computer and light up accordingly. E.g. 10 Red, 0 Green, 10 blue to make purple I've found several projects that will light up the leds when the usb is plugged in but id like to control which leds are lit. Is anyone able to draw an circuit diagram for me or suggest anything to help me make this project as i can probably program something to send the output from the computer but its the wiring of the controller etc that im not so good at figuring out.

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Jul 20, 2009. 6:46 AMorksecurity says:
Alternatively, if you want lower-level digital hardware hacking, you could use a USB-to-parallel-port or USB-to-serial-port adapter, feed that into an appropriate set of latch or shift register chips, then take the output of those to control the LEDs. Microcontrollers are good swiss army knives, but sometimes it's worth thinking about a do-only-one-thing screwdriver.
May 18, 2010. 2:31 PMWin7Maniac says:
Could you post your code, or make an instructable?  I am trying to do something similar, and I'm sure others would benefit as well! Thanks!
Jul 20, 2009. 6:43 AMfrollard says:
A standard arduino has 3 analogue pwm outputs and can make 8 bit colour changes in each colour channel (256 colours each)... It communicates with a computer via serial over built in usb chip - then you can write programs on the computer to tell it what to do. The arduino itself would need an led driver to have enough power for bigger leds - a few transistors would do the trick.
Jul 24, 2009. 10:23 PMfrollard says:
Great job searching and getting lots of info - the arduino.cc website has a TONNE of learner scripts to teach you how to turn an led on, and off...with code examples for everything. It just gets more exciting from there what you can do :D
Sep 12, 2009. 11:49 AMfrollard says:
This is old enough it might warrant a new question - noone will be notified that you made the update.

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