Definitions Library

RGB

- Red Green Blue.  These are the electronic primary colors. all colors contain a combination of these.  White is a balance the three colors.  Typically with LED's, there are 256 intensities between all the way off (0) and all the way on (255).  With 256 levels of Red, 256 levels of Green and 256 levels of Blue we get:  256x256x256 = 16.777216 million colors.

DMX

- the communication standard for lighting equiptment like stage lighting and almost everything LED. 

Electrically, it is a two wire (data + and data -) and signal ground.  The data pumped though these wires by some sort of DMX console (source), is connected to each DMX decoder or other DMX controlled (listener) device. 

The connection path leaves the source and connects to each listener, a wall washer decoder or self contained DMX compatable light fixture or device (smart devices), and connects like a daisy chain where it connects into one and out of that one and into another until all the devices (listeners) are conected to the source.

The structure of the changing electrical signals makes a map of 512 channels.  Each channel can have a value between 0 and 255.  The LED smart lights, DMX decoder/drivers and any other devices, know what to do with this value.  Most DMX decoders for LED's are 3 channels, one for Red, one for Green and one for Blue.  Smart devices will have a manual with a table describing what a value range on a channel will make the device do.   So some devices use 3 DMX channels and some use more.

In many displays, 512 DMX channels are nowhere near enough to do get the job done.  So, 512 channels is a universe and mulitple universes can be kept in sync by the source device.  Each universe chain will plug into a separate port at the source.

A DMX console or software on your PC is made up of volume controls like a sound mixer board.  Only instead of a zero to one hundred percent output of a sound device, the output is a number between 0 and 255 for that channel.  As mentioned earlyer, the lights know what to do with these numbers.

Dongle or USB to DMX interfaceThe software for most of the DMX lighting packages out there is a free download.  The interface to communicate the sofwares output stream to the lights must be purchased.  Many including myself call this interface a Dongle.  It converts standard USB or ethernet output to DMX.  Usually, a single universe of lights will be a USB Dongle and mulitple universe systems will use ethernet - network based control flow.