Table of Contents

Lighting Control Concepts

DMX512 System

DMX512 (Digital Multiplex with 512 pieces of information) is a multi-drop serial communication protocol and the standard by which lighting control systems interface with lighting equipment.

A DMX controller transmits packets of 512 8-bit values at a rate of up to 44 per second over a balanced cable.  This is known as a DMX universe.  An 8-bit value has the range of 0 to 255 decimal.  Since the values are sent sequentially, each one can be referenced by its position (address) in the packet.

Initially, DMX was generated by a physical control desk and controlled banks of dimmer circuits, which in turn were connected to conventional lighting instruments (luminaires).  The value (level, often expressed as 0-100%) addressed to each dimmer circuit controlled the brightness (intensity) of the luminaire connected to it.

Over time, more sophisticated (so called “intelligent”) lighting equipment was developed as well as computer-based controllers and DMX values were used to set attributes such as color, aperture, position, etc. in addition to dimmer levels.

RDM

Remote Device Management (RDM) is a protocol enhancement to USITT DMX512 that allows bi-directional communication between a lighting controller and attached RDM-compliant devices over a standard DMX line. This protocol allows configuration, status monitoring, and management of these devices in such a way that it does not disturb the normal operation of standard DMX devices that do not recognize the RDM protocol.

The figure below illustrates how a lighting system, consisting of conventional dimmers and intelligent fixtures controlled by a console, might be configured.

Lighting System

Patching

Most lighting control systems (including NEO) allow the assignment (called patching) of DMX addresses to logical controls, usually called channels and/or fixtures.  Once patched, the operator uses these controls to set the attributes of the dimmer(s) or fixtures(s) assigned to them.

Typically, a control can have multiple DMX addresses assigned to it.  However, the converse is not allowed usually (i.e. a given DMX address can be assigned to one control only).

The figure below shows an example of a simple patch map.

Patching Example

Fixture Profiles

Intelligent fixtures can have many functions and can require a block of many DMX addresses to control them.  Most lighting control systems (including NEO) have available a library of fixture profiles that map functions to (relative) DMX addresses.  Once a profile is patched, the operator can manipulate the fixture using labelled controls.

For example, the Vari-Lite VL2600 fixture patched in the example above has functions for shutter, dimmer, color wheels, gobo wheels, focus, iris, pan, tilt, etc., and requires a block of 42 DMX addresses.

How did we do?

Understanding Tracking

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