Now, this is the fun part: building up your circuitry! I've found this (http://www.instructables.com/id/Arduino-controlled-light-dimmer-The-circuit/) very interesting, but due to some availability problems, I had to improvise / change some parts. For instance, it was written based on the H11AA1, which is an optocoupler with 2 leds in parallel (one against the other), that is not so common in Latam. As the zero-cross detector circuit had a bridge rectifier just before the optocoupler, I decided to use a single led optocoupler, without zero cross detector in it, but that delivers a pulse signal within the 5V limit of the arduino. The Triac TIC206 is another part that I had to change, using a BT136 instead (up to 600V, 4 A on state, 25A non repetitive peak) to handle my dichroic lamps. All other parts were used as described in the Instructables. As you might have imagined, the simplest thing on it was to replicate 3 more times the TRIAC part of the circuitry, to deal with all channels that I needed. A pro tip on the Triacs: bear in mind the Terminal1 and 2 on the Triac, as if you deliver voltage to the wrong terminal, IT WON'T FIRE to the other terminal! (OK, I had a fight, long, ugly fight, with the Triac, just to find out that I was delivering voltage to the wrong terminal! )