Understanding DMX

An introduction to DMX512 for lighting control.

What is DMX?

DMX512 (Digital Multiplex 512) is the standard protocol for controlling stage lighting. Developed in 1986, it's used worldwide for theatrical, concert, and architectural lighting.

Key concepts

Channels

• A DMX universe has 512 channels.
• Each channel sends a value from 0 to 255.
• Channels control specific functions (dimmer, color, position).

Fixtures

Each fixture uses one or more channels:

• Simple dimmer: 1 channel.
• RGB LED: 3 channels (Red, Green, Blue).
• Moving head: 8-40+ channels.

Addressing

Fixtures are assigned a start address (1-512):

• A fixture at address 1 with 4 channels uses channels 1-4.
• The next fixture could start at address 5.

Each channel should belong to only one fixture.

Universes

One universe equals 512 channels

For larger shows:

• Universe 1: channels 1-512.
• Universe 2: channels 513-1024 (conceptually).
• Each universe is independent.

Multiple universes

Connect multiple universes via:

• Multiple DMX cables.
• Art-Net over Ethernet (unlimited universes).
• sACN (Streaming ACN).

Channel values

The 0-255 range

Common uses

Fixture modes

Many fixtures have multiple DMX modes:

Example: LED Par

3-channel mode:

• Ch 1: Red
• Ch 2: Green
• Ch 3: Blue

7-channel mode:

• Ch 1: Dimmer
• Ch 2: Red
• Ch 3: Green
• Ch 4: Blue
• Ch 5: Strobe
• Ch 6: Color macros
• Ch 7: Mode select

The fixture's physical setting must match the mode in your software.

Address planning

Simple example

Best practices

1. Leave gaps in the address plan so you can add fixtures later.
2. Group fixtures of the same type together.
3. Keep a written record of every patch.
4. Start fixture addresses on round numbers (1, 10, 20, 50, 100).

Physical connections

DMX cables

• 5-pin XLR (professional standard).
• 3-pin XLR (common but not to spec).
• Never use audio cables for DMX.

Daisy chain

Connect fixtures in series:

Controller → Fixture 1 → Fixture 2 → Fixture 3 → Terminator

Termination

Add a 120Ω terminator at the end of long runs to prevent signal reflection.

Cable limits

• Maximum 300m (1000ft) per run.
• Maximum 32 devices per run.
• Use splitters for longer or larger installations.

Art-Net

For Ethernet-based DMX:

Advantages

• Multiple universes over one cable.
• Longer distances (100m per segment).
• Network infrastructure compatibility.

Addressing

Art-Net uses Net/Subnet/Universe:

• Net: 0-127.
• Subnet: 0-15.
• Universe: 0-15.

Simple setup: Net 0, Subnet 0, Universe 0, 1, 2, and so on.

Troubleshooting

No output

1. Check cable connections.
2. Verify the fixture is in DMX mode.
3. Confirm the address matches.
4. Check for address conflicts.

Flickering

1. Check for cable damage.
2. Add or verify termination.
3. Reduce cable length.
4. Check for electrical interference.

Wrong behavior

1. Verify the fixture mode matches the patch.
2. Check channel assignments.
3. Confirm value ranges.

Related

• DMX Patching
• Art-Net Setup
• Address Space Panel