History and Standards
– DMX512 developed by the Engineering Commission of USITT
– DMX512 standard created in 1986, revised in 1990 and 2008
– Approved by ANSI in 2004
– Current standard known as E1.11 – 2008, USITT DMX512-A, or just DMX512-A
Network Topology and Physical Layer
– DMX512 network uses a multi-drop bus topology
– Nodes are connected in a daisy chain
– Consists of a controller and slave devices
– Data transmitted over a differential pair using EIA-485 voltage levels
– Network length should not exceed 400 meters
– Maximum of 32 unit loads on a single bus
– Network can be expanded using DMX splitters
– Network wiring consists of a shielded twisted pair with a characteristic impedance of 120 ohms
Connectors
– DMX512 specifies the use of five-pin XLR style connectors
– Female connectors used on transmitting ports and male connectors on receiving ports
– Use of any other XLR style connector is prohibited
– Three-pin XLR connector is commonly used but prohibited by the DMX512 standard
– Eight-pin modular connectors (8P8C or RJ-45) allowed for fixed installations
DMX512 Protocol and Timing
– DMX512 uses asynchronous serial data transmission at 250 kbit/s
– Each frame consists of a break condition, mark-after-break, start code, and up to 512 slots of channel data
– Timing parameters may vary
– Maximum-sized packet takes approximately 23 ms to send
– Minimum break-to-break transmit time can be achieved by adjusting timing parameters
Practical Considerations and Wireless Operation
– DMX512 is popular due to its robustness
– Cable faults and addressing errors can cause issues
– Multiple DMX sources on a single chain can cause problems
– Wireless DMX512 adapters have become popular
– Wireless DMX512 networks can function over distances exceeding 3,000 feet
– Most wireless DMX512 links are limited to a maximum distance of 1,000-1,500 feet
– Wireless DMX systems use frequency-hopping spread spectrum technology Source: https://en.wikipedia.org/wiki/DMX-512
This article needs additional citations for verification. (February 2011) |
DMX512 is a standard for digital communication networks that are commonly used to control lighting and effects. It was originally intended as a standardized method for controlling stage lighting dimmers, which, prior to DMX512, had employed various incompatible proprietary protocols. It quickly became the primary method for linking controllers (such as a lighting console) to dimmers and special effects devices such as fog machines and intelligent lights.
 XLR5 pinouts | |||
| Type | Lighting control | ||
|---|---|---|---|
| General specifications | |||
| Hot pluggable | Yes | ||
| Daisy chain | Yes | ||
| External | Yes | ||
| Cable | 2 pair, 24 AWG, 7x32 stranded, tinned copper, 6.9 left hand twist/ft | ||
| Pins | 5 | ||
| Connector | 1 | ||
| Electrical | |||
| Max. voltage | +6 VDC per pin | ||
| Max. current | 250 mA | ||
| Data | |||
| Bitrate | 250 kbit/s | ||
| Protocol | asynchronous, half-duplex, serial protocol over a two-wire bus | ||
| Pinout | |||
| Pin 1 | Signal Common | ||
| Pin 2 | data 1- | ||
| Pin 3 | data 1+ | ||
| Pin 4 | data 2- | ||
| Pin 5 | data 2+ | ||
 XLR3 pinouts | |||
| Type | Lighting control | ||
|---|---|---|---|
| General specifications | |||
| Hot pluggable | Yes | ||
| Daisy chain | Yes | ||
| External | Yes | ||
| Pins | 3 | ||
| Connector | 1 | ||
DMX512 has also expanded to uses in non-theatrical interior and architectural lighting, at scales ranging from strings of Christmas lights to electronic billboards and stadium or arena concerts. It can now be used to control almost anything, reflecting its popularity in all types of venues.
DMX512 uses a unidirectional EIA-485 (RS-485) differential signaling at its physical layer, in conjunction with a variable-size, packet-based communication protocol. DMX512 does not include automatic error checking and correction, and therefore is not an appropriate control for hazardous applications, such as pyrotechnics or movement of theatrical rigging. However, it is still used for such applications. False triggering may be caused by electromagnetic interference, static electricity discharges, improper cable termination, excessively long cables, or poor quality cables.
