The 2005 RGB Christmas Light Project: Pixel Schematic

Not much to it at all, actually... Note that the R1 is a 1/2 watt termination resistor and only needs to be installed on the last fixture in the DMX chain. Up to 32 of these units can be connected to a single RS-485 bus without loading it down too greatly.

For a larger installation, one can use opto-splitters to create multiple busses.

A 512 channel universe can accommodate 170 three channel pixels.

Scroll down to see the schematic (it's too wide to fit right here).