Curiosidades Protocolos de Controlo de Iluminação

[Rui Garcia]

DMX 512
DMX is a lighting industry standard way of controlling lighting equipment. The whole idea behind DMX as a standard is that it allows equipment from one manufacturer to talk to that made by another. DMX-512 allows for one controller (like a lighting desk)to control many lights. DMX is limited to controlling 512 separateparameters, that's where the name DMX-512 comes from. DMX-512 is a protocol for controlling (at a basic level) the brightness oflights in a theatre (it is vary capable and can be used for controlling moving lights, smoke machines, strobe lights etc.). It basically consists of one 8-bit (on or off) signal for each light whichsets the brightness level (0-100%) of the light to one of 256 levels.

AMX192
AMX192 is a control protocol standard for dimmers first introduced around 1975 as Strand proprietary multiplexed dimmer control system. This sytem became widely used with Strand's extremely popular Light Palette and CD80 dimmers that first appeared in 1979. The AMX192 standard, adapted by the United States Institute for Theatre Technology, is non proprietary and may be used by all manufacturers. The AMX192 standard was introduced at 1985. The origins of this standard come from a control protocol originally developed by Strand Lighting (Strand Century Inc.). This protocol is used by a large installed base of equipment manufactured by Strand and many other manufacturers.

Ethernet in light controlling
Ethernet is the most commonly used standard computer communications protocol used in local area networks. Moving lights, modern dimmers and lighting control desks all contain computers, so it coming to wide use for lighting control as well. Ethernet is capable of controlling massive numbers of lights, but at the moment Ethernet light controlling suffers from slightly lower reliability and less standardization than traditional DMX-512 interface. Ethernet using twisted pair wiring is coming to the lighting industry controlling, but the manufacturers have not yet have agreed on a common Ethernet protocol. Current Ethernet standards define the pyical network and addressing, but there are no standard for the format and content of the packets to be used for lighting equipment controlling. Nowadays there are some implementations of Ethernet based light controlling but those are proprietary solutions which are not compatible with each other. Some implementations run on Ethernet level and need their own Ethernet segments, while some other rely on using TCP/IP protocol running on top of the Ethernet. Generally speaking Ethernet cabling is cheaper than currently used cabling systems and it can replace many different control cabling, so in not-too-distant future Ethernet an take an important role in theatrical and lighting control technology. There are nowadays several protocols cometing on the Ethernet lighting control. ACN (or the ANSI BSR E1.17 standard) is the next generation control protocol that is under development by ESTA (Entertainment Services and Technology Association). It will operate using Ethernet and is intended partly to address the limitations of DMX512. This standard is under development at the moment. Art-Net is a protocol used, for example, for things like theaters to transport lighting data over Ethernet. The protocol is designed by Artistic Licence and put into the public domain. Its purpose is to allow transfer of large amounts of DMX512 data over a wide area using standard networking technology.

MIDI Show Control
MIDI is short for musical Instruments digital Interface. It was originally used to link keyboards and music syntetizers. MIDI is now used for linking lighting boards together, controlling dimmers and running shows. MIDI is event based, that is messages are sent to indicate what must changed, and the value to which it must be changed, rather than constantly updating the receiver. The data rate of MIDI is 31.5 kBaud. MIDI interface is based around opto-isolated current loops. A typical application for MIDI in show lighing is to leave the "controller" as a device that stores sets ofdimmer levels (called a "scene" memory or "preset") and you could selectwhich scene to play from any MIDI device. This would imitate the functionality found on a lot of lighting boards (some advanced boards have even MIDI interfaces). Depending on the application the controlling can be done using MIDI Show Control messages (standard for control messages being passed over MIDI) or justsimple note-on note-off messages with different notes triggeringdifference memories on your controller. MIDI can be used to control the dimmers directly. There are a couple of MIDI dimmer packs out there. Technically MIDI a lot easier protocol to work with than DMX, since the bit-rate is so much less.But the use of MIDI is not really the standard for lighting control, which means your options will be limited if you plan to use MIDI for this (you are limited to few manufacturers, and changing to use devices from other manufacturers later can be hard).

RS-232 lighting control
RS-232 is not widely used for controlling lighting instruments in the lighting industry. There are some disco effect (quite rare) that can take in RS-232 signal. In some lighting applications controlling lighting through RS-232 interface could be useful. Usually this is accomplishes by using a special converter box which takes in RS-232 signal and outputs suitable control signal that the lighting instruments can use. There is a lot of entertainment kit designed to takeRS-232. Any company which is trying to get out of straight theatre ofdiscos will have such kit, because it allows them to be used in museums,commercial developments, shopping malls and restaurants with boutiquediscos run off central time cues. RS-232 systems generally allow the signal source to generate a one word string (or sometimes longer control word). The RS-232 listening devices are simplyprogrammed to respond to that string. It is very basic really, but veryeffective because it allows you to interface anything - all device suppliers will give you a documentation or library of commands for their kit (different manufacturers use different commands). In many special applications which combine technologies from different technology areas then RS-232 is usually the only sensible interface to use. It is universal for interfacingAV/Lighting/Comms/Networking/Blinds/Doors/HVAC and everything else in abuilding management systems (BMS). There are variousprotocols by specific BMS manufacturers, but ALL of them have RS-232modules. Why? It is the universal protocol for such equipment.

Home automation and lighting control

X-10
X-10 is a power line carrier protocol that allows compatible devices throughout the home to communicate with each other via the existing 110V wiring in the house. Using X-10 it is possible to control lights and virtually any other electrical device from anywhere in the house with no additional wiring. X10 is a communications "language" that allows compatible products to talk to each other via the existing 110V electrical wiring in the home. X10 devices can be categorized into 3 distinct groups: Transmitters, Receivers and Transmitter/Receivers (2 Way X10 devices). X10 Transmitter devices send a coded low voltage signal that is superimposed over the 110VAC current. Any X10 Receiver device plugged into the household 110V power supply will see this signal. However, the Receivers will only respond when it sees a signal that has its address. Up to 256 different addresses are available. If you want more than one device to respond to the same signal, simply set them to the same addresses. X-10 operates at 120 kHz frequency range. X-10 adds short bursts of 120 kHz carrier after each mains zero crossing to send data. Each data bit takes two zero crossings, so the data rate is 60 bps. This is enough for slow control applications.

DALI
The drive for Energy Conservation and Intelligent Building Automation has led to the development of the DALI standard for control of Lighting Networks, especially those involving Fluorescent Ballasts. Backed by the major Lighting manufacturers in the world, the DALI interface allows for low cost control of large networks. DALI (Digital Addressable Lighting Interface) is a quite new industry standard to lighting control systems. DALI is supported by the main lamp and ballast manufacturers in Europe (Helvar, Osram Philips, and Tridonic). Backed by the major lighting manufacturers in the world, the DALI interface allows for low cost control of large networks. The DALI system mentioned as extension to IEC60929 standard.
DALI is a dedicated communication interface for the control of lighting systems at local room level. It has been developed specifically for optimum lighting control, both in Local Room Control applications and when interfacing with Building Management Systems. The DALI protocol is exclusively designed for lighting and aims at filling the gap between the standard 1-10 V analog control interface and the more complex universal bus systems, which are too advanced for many applications. DALI interface is suitable for mid-size rooms and stand-alone systems. DALI system is the combination of ballast switching and dimming via the control wire with ballast addressing. The key feature of DALI is individual ballast addressability, which enables up to 64 different luminaires on the same control circuit to be switched and controlled independently. The luminaires on a single circuit can be combined in up to 16 freely definable groups, in which individual light can be assigned to one or more groups. Programmablity allows installations to be reconfigured without the need for costly wiring changes.

EIB (European Installation Bus)
The European Installation Bus (EIB) is an open, comprehensive system which covers all aspects of Building Automation. It is managed by the neutral EIB Association. The European Installation Bus is designed as a management system in the field of electrical installation for load switching, environmental control and security, for different types of buildings. The InstallationBus can be installed in large buildings such as business premises, schools, hospitals, factoriesand administration premises as well as in domestic residences. Its purpose is to ensure themonitoring and control of functions and processes such as lighting, window blinds, heating,ventilation, air-conditioning, load management, signaling, monitoring and alarms. The EIB is an intelligent building control system which is able to control, regulate, measure, switch, service and monitor. Its basis is a communications bus which lies in parallel with the 230V mains network. EIB is a fully peer-to-peer network, which accommodates up to 65?536 devices. The logical topology allows 256 devices on one line. The EIB system allows the bus devices to draw their power supply from the communication medium, like Twisted Pair or Powerline (230 V mains). The EIB protocol is today supported by several media, like Twisted Pair, Powerline, RadioFrequency and Infra-Red. It is of course always possible to connect gateways to other media. Possible media types:

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[jaimereis]

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