A standard $35 Raspberry Pi computer runs a program that generates the onscreen interface, and sends commands via USB to a DMX controller continuously. The DMX controller then sends DMX commands to the light fixture to change the color. The hardware was chosen for cost and durability, and the software was developed on the platform and is available for free in source and binary format so you can begin hacking right away. Here is what you'll need ( as pictured ):
1. Raspberry Pi
The Raspberry Pi is an amazing $35 credit card sized computer that contains all the basic features of a "real" computer, including a free pre-built Linux operating system ( via SD card ), USB for keyboard and mouse, and most impressively a full HDMI video output. If you are new to the Raspberry Pi ( or raspi ) we strongly suggest you get your mitts on one as soon as possible - its a great platform for anyone interested in knowing more about how computers work, and you can actually write programs on it!
2. USB | DMX Controller
The raspi has a built-in I/O connector for doing all sorts of cool things, but for this project we chose to use one of the USB ports as our output interface because its simpler and more rugged than using breadboards and ribbon cables. To get things into DMX (digital light control) format, we will be using a Velleman USB to DMX interface. This can be bought in either kit or pre-built form, and is a really a great introduction to controlling DMX devices from a computer. Once you have this controller you'll find it a great tool for any lighting control project you may cook up in the future.
3. DMX light fixture
Pretty much any DMX controlled light fixture that has red, green, or blue channels will work, and in fact you can chain together several if you want t control a whole bank of lights from your raspi. In this example we are using a Chauvet LEDSplash 200B spotlight because we found one cheap online for about $60 and its very bright and runs cool. If you have a DMX dimmer and standard PAR cans that's fine too, its only important that you have a device that can receive red, green, and blue intensity channels.
4. HDMI ( or NTSC monitor )
Perhaps the best feature of the raspi is its HDM interface ( compare with Arduino video output ), which provides a full 1920x1080 graphics resolution to any TV screen that has an HDMI input. In this example we used a cheap Vizio monitor that we had in our kitchen, and functions nicely for a video monitor. It might be interesting to to use this kind of system as a starting point for a TV back light project or similar living room light effects when you move it into your living room since you have the video interface right there.