About DMX control

DMX512 is a standard protocol developed for controlling lighting and dimmers from a lighting board in theatre environments. As it has a high transmission speed, it places certain demands on installation and the choice of cables and connectors.

 

DMX control has now found applications in other environments due to developments in light sources and requirements for coloured lighting in outdoor applications etc. DMX, RGB and LED are often considered equivalent. Put simply, DMX uses a control unit to control all the loads.

DMX is a centralised control system.

 

DMX compared with DALI

Comparing DMX with DALI reveals more differences than similarities. The development of DALI focused on energy-efficient fluorescent tube lighting in public environments where people stay and work. The impact of DALI has been enormous despite this limitation, but its simplicity was the decisive factor. Multiple control units can control all or parts of the loads.

DALI is a decentralised control system.

 

 

Control protocols
DALI
DMX
Speed Slow Fast
Number of addresses 64 512
Multiple devices with the same address No 1) Yes
Automatic addressing Yes No 2)
Centralised control No Yes
Decentralised control Yes No
Cable length 300 m 300 m
Cable requirement No Yes, Cat-5
End-of-line resistor No Yes
1) Converters for 1-10 V are common.
2) RDM luminaires can be addressed using software.

DMX is under development

DMX is also available in a recently updated version, RDM, that enables loads to be addressed using DMX cable and software. This requires the loads and the software to be correctly selected. The most common method of DMX addressing uses DIP switches on each device.

 

Installations

DMX is highly suitable for use in fixed installations using standard network cables normally used for computers. DMX cables and connectors used to be made for theatre applications, with far too many variations and an unnecessarily robust design. Fagerhult prefers to use Cat-5 connectors and we recommend cables of the same standard.

 

Basic rules for installation

  • When installing it is important to follow the recommendations for a reliable system.
  • Use Cat-5 or better network cables.
  • Always connect cables from device to device.
  • Never create branches or closed loops.
  • Never finish with an unused cable loop.
  • Loads greater than 20 in number need to be distributed using a multiplexer (distribution device).

Daisy chain

The technical expression ‘daisy chain’ describes a method of connecting devices in series (although in fact all devices are connected in parallel). This applies in particular to DMX. To simplify installation, and make it easier to connect further devices, Fagerhult use two connectors in some luminaires, such as the Pleiad LED wallwasher.

Large installations also require the loop to be balanced using an end-of-line resistor in the luminaire furthest from the control unit.

If in doubt, contact Fagerhult for information on how to proceed with a system.