What is DMX lighting control?
Quick answer
DMX (Digital Multiplex) is a standard protocol for controlling lighting and effects equipment, using a unidirectional data stream over a 3- or 5-pin XLR cable to send 512 channels of control data per universe.
DMX512, the full name, was developed in 1986 by the USITT and later adopted as ANSI E1.11. It transmits 512 channels of 8-bit data per universe, with each channel typically controlling a parameter like intensity, color, or pan/tilt. The signal is sent at 250 kbps, allowing for up to 44 updates per second.
In a DMX system, a controller (lighting desk or software) sends packets to daisy-chained devices. Each device is assigned a start address, and it reads the appropriate channels from the data stream. Termination with a 120-ohm resistor is required at the end of the chain to prevent signal reflection.
While DMX is primarily for lighting, it can also control fog machines, moving heads, and LED strips. Modern systems often use DMX over Ethernet (Art-Net, sACN) for larger installations, but the core protocol remains the same. For audio professionals, understanding DMX is essential for integrated AV productions.
Key things to consider
- DMX512 uses a single universe of 512 channels; multiple universes can be linked for larger systems.
- Devices are daisy-chained with a maximum cable length of about 300 meters (1000 feet) without a repeater.
- Each device has a start address; addresses are set via dip switches or software.
- Termination is critical: a 120-ohm resistor must be placed on the last device to avoid data errors.
- DMX is unidirectional; newer protocols like RDM (Remote Device Management) allow bidirectional communication.
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