Arduino RGB Mixer

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This page describes how to build a simple LED RGB color mixer using an Arduino and OLA and QLC. The Arduino is programed to emulate a DMX USB Pro.

Parts:

• LED strip lights, Ikea has a set which are reasonably cheap and come with mounting brackets: Dioder - $50
• A power supply for the Led lights, make sure it can provide enough current for the amount of leds you plan to use. You can use the one from the Ikea lights.
• An Arduino, I used the Duemilanove - $30
• Parts to make a driver circuit: 3 x 2N2222 transistors, 3x 2.2k resistors, small PCB - $10
• A 110ohm resistor (or 100 + 10 ohm) to disable the auto-reset on the new Arduino boards.

In the example above the Ikea leds run from 12V and draw ~420mA when all colors are on so you need to make sure the driver circuit and power supply is sized correctly.

Hardware

The LEDs use 12V while the Arduino supplies 5V so we need to make a driver circuit. The one below should be good up to 800mA per channel or so.

You need one of these per channel. The inputs should be connected to the PWM pins on the Arduino (pins 3, 5 & 6 on a Duemilanove). Make sure you connect the ground of both circuits.

Arduino Software

Download the latest sketch file from http://code.google.com/p/linux-lighting/downloads/list

Disable Auto-Reset

The newer Ardiuno boards auto-reset when the serial connection is established which causes problems with OLA. To disable the auto-reset connect a 110 ohm resistor between the RESET and 5V pins. Note that you need to remove this when you program your Arduino.

Host Software

Download and install OLA and either ola-examples or QLC. See the documentation for either/both products for getting it installed. The device should show up as a DMX USB Pro, the first three channel control the red, green & blue intensities.

Future Work

• Use the 3 other PWM pins to control a second LED strip
• Expand the PWM outputs with http://www.arduino.cc/playground/Learning/TLC5940
• Set the start address using a DIP switch