DMX

DMX512 (commonly called DMX) is the industry-standard communication protocol used to control theatrical lighting, stage equipment, architectural lighting, and many Christmas lighting controllers. Although originally developed for dimmers, DMX is now used to control moving lights, RGB fixtures, fog machines, relay controllers, pixel gateways, and numerous other entertainment devices.

DMX remains one of the most widely supported lighting control standards in the world.

Figure 1 – DMX512 is the standard communication protocol for entertainment lighting.

Overview

DMX transmits lighting control information from a controller to one or more receiving devices.

A typical DMX system consists of:

Sequencing software or show player
DMX controller or gateway
DMX cable
One or more DMX devices

Examples of DMX devices include:

RGB floodlights
Moving-head fixtures
Dimmers
Relay controllers
Fog machines
Pixel gateways

How DMX Works

DMX sends channel values continuously over a serial RS-485 connection.

Each device is assigned a starting channel address.

Every device listens to the data stream and responds only to the channels assigned to it.

A typical signal path is:

xLights or FPP
      ↓
DMX Controller
      ↓
RS-485 DMX Cable
      ↓
DMX Devices

DMX Channels

One DMX universe contains:

512 control channels

Each channel contains a value from:

0 to 255

Examples:

Dimmer = 1 channel
RGB fixture = 3 channels
RGBW fixture = 4 channels
Moving light = 10 to 30+ channels

Daisy-Chain Wiring

DMX devices are connected in a daisy chain.

Controller
    ↓
Device 1
    ↓
Device 2
    ↓
Device 3

Unlike Ethernet, DMX is not normally wired in a star configuration.

The final device should normally be terminated with a 120-ohm termination resistor.

DMX Connectors

Professional DMX equipment commonly uses:

5-pin XLR

Many Christmas-lighting products use:

3-pin XLR
RJ45 connectors
Screw terminals
Phoenix connectors

Connector style varies, but the signaling method remains the same.

RS-485

DMX uses the RS-485 electrical standard.

Advantages include:

Long cable lengths
Excellent noise immunity
Reliable differential signaling
Multi-device communication

RS-485 defines the electrical interface, while DMX defines the lighting protocol carried over it.

DMX and Pixels

DMX does not directly control smart pixels.

Instead:

Pixel controllers receive E1.31 or DDP.
The controller converts that data into pixel signals.

However, many pixel controllers also include one or more DMX outputs for controlling conventional lighting equipment.

DMX and E1.31

E1.31 transports DMX-style channel data over Ethernet or Wi-Fi.

An E1.31-to-DMX gateway converts network packets into a physical DMX output.

This allows modern sequencing software to control traditional DMX equipment using standard IP networks.

Typical Christmas Lighting Uses

DMX is commonly used for:

Floodlights
Moving-head lights
Relay controllers
Fog machines
Snow machines
Laser projectors
Pixel gateways
Stage lighting

Common Configuration Problems

Typical DMX problems include:

Incorrect starting address
Duplicate addresses
Missing termination resistor
Reversed data wiring
Faulty RS-485 cable
Incorrect connector wiring
Using microphone cable instead of DMX cable

Advantages

Industry standard
Extremely reliable
Long cable lengths
Excellent electrical noise immunity
Wide equipment compatibility
Simple addressing

Limitations

Limited to 512 channels per universe
Daisy-chain wiring
One-way communication
Lower bandwidth than Ethernet
Intended primarily for conventional lighting

Christmas Display Recommendations

DMX remains an excellent choice for:

Conventional lighting fixtures
Moving-head lights
Floodlights
Relay controllers
Professional stage equipment

For individually addressable smart pixels, protocols such as DDP and E1.31 used with pixel controllers are generally more appropriate.

DMX

Contents

DMX