Fulfilling our customers’ requests , here at 01™ Mechatronics , we are on a process of adding DMX 512 compatibility to our Supermodified Servos . But what does DMX mean? DMX is a control system for stage lighting and effects.
If we go into more detail, we can describe it as a standard for digital communication networks that are commonly used on linking controllers (such as a lighting console) to dimmers and special effects devices such as fog machines and intelligent lights.
DMX can now be used to control almost anything, reflecting its popularity in theaters and venues. Soft Lab NY, embraced DMX technology on led lights, over an amazing installation of 100 mirrored panels, each one actuated by our Zeus Supermodified Servos. (read about it on our references section).
DMX512 employs EIA-485 differential signaling at its physical layer, in conjunction with a variable-size, packet-based communication protocol. It is unidirectional.
A DMX512 network employs a multi-drop bus topology with nodes strung together in what is commonly called a daisy chain. A network consists of a single DMX512 controller – which is the master of the network — and one or more slave devices. For example, a lighting console is frequently employed as the controller for a network of slave devices such as dimmers, fog machines and intelligent lights.
Each slave device has a DMX512 “IN” connector and usually an “OUT” (or “THRU”) connector as well. The controller, which has only an OUT connector, is connected via a DMX512 cable to the IN connector of the first slave. A second cable then links the OUT or THRU connector of the first slave to the IN connector of the next slave in the chain, and so on. For example, the block diagram above shows a simple network consisting of a controller and three slaves.
The specification requires a ‘terminator’ to be connected to the final OUT or THRU connector of the last slave on the daisy chain, which would otherwise be unconnected. A terminator is a stand-alone male connector with an integral 120 Ω resistor connected across the primary data signal pair; this resistor matches the cable’s characteristic impedance. If a secondary data pair is used, a termination resistor is connected across it as well.
Although simple systems (i.e., systems having few devices and short cables) will sometimes function normally without a terminator, the standard requires its use. Some DMX slave devices have built-in terminators that can be manually activated with a mechanical switch or by software, or by automatically sensing the absence of a connected cable.
A DMX512 network is called a “DMX universe”. Each OUT connector on a DMX512 controller can control a single universe. Smaller controllers may have a single OUT connector, enabling them to control only one universe, whereas large control desks (operator consoles) may have the capacity to control multiple universes, with an OUT connector provided for each universe. ( info source: wikipedia)
Also keep in mind :
- A DMX system contains one controller (transmitter) and receiver(s)
- Information is transferred by modulating the two signal wires in opposite way. Ground is needed as reference
- A receiver has to be given an address. This is a number between 1 and 512.
- This address cannot be changed via the DMX connection. DMX is based on RS485 communication. RS485 protocol is two way communication, this is not implemented in DMX (one way only)
- DMX is invented to replace a multiplexed analog system
- In DMX communication there is no address info. The receiver counts the messages
- Random addressing is not possible. Addresses cannot be left out.
- A DMX value can mean anything, depending on receiver. For luminaires with intensity only most often a linear intensity curve is used.
- Standard: NE1.11, USITT DMX512-AP, maintained by ESTA
Below you can watch an educational guide about dmx technology, uploaded on youtube by user LearnLizard
DMX technical characteristics:
Number of units max. 30 (Using boosters: unlimited)
Number of addresses 512 max
Signal level several hunderds of millivolts
Speed 40 times 512 values / second
+/- 250 kbaud
Termination end of the line, 120 Ohm
Cable length max. 500m, (Using boosters: unlimited)
Cable type Shielded twisted pair 100-120 Ohm
Cat.5 S/UPT, F/UTP, SF/UTP
Cat.6 U/FTP, S/FTP, S/STP
Cat.7 S/FTP, S/STP
Cable topology serial (line)
Termination 120 Ohm
Safety DMX is SELV