31/10/2015

31/10/2015

The Development of Lighting Protocols EM2S13

University of South Wales

James Walton

14006847

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Contents

Where it all Began ...........................................................................................................................3

The Introduction of Multiplexing .....................................................................................................4

Analogue ...............................................................................................................................................................4

AMX 192 .................................................................................................................................................................4

D54 .........................................................................................................................................................................4

Digital ....................................................................................................................................................................5

The Standardisation of DMX512 ......................................................................................................6

TCP/IP and Networking ...................................................................................................................8

Transport Protocols ..............................................................................................................................................8

Realtime Protocols ...............................................................................................................................................8

The Future ........................................................................................................................................9

Session Data Transport ........................................................................................................................................9

Device Management Protocol ............................................................................................................................ 10

Appendices ..................................................................................................................................... 11

Figure 1 – Davies Black Sabbath 1976 .............................................................................................................. 11

Figure 5 – Century Strands D54 Signal Parameters ........................................................................................ 13

Figure 6 – D54 signal, Oscilloscope Reading .................................................................................................... 14

Strand’s D54 analogue protocol structure over a pair of terminated cable. .................................................. 14

Figure 7 – ILDA Pinout........................................................................................................................................ 14

Figure 10 – RS485 Duplex Communication ....................................................................................................... 15

Figure 11 - Pangolin Flashback 4 – SE ............................................................................................................. 16

Figure 12 - Typical DMX vs DMP Messages ...................................................................................................... 16

Figure 13 – Typical ACN and Streaming ACN Messages ................................................................................. 17

Figure 14– DDL Communication........................................................................................................................ 17

Figure 15 – Unreliable and Reliable Messages ................................................................................................ 18

Figure 16 – The Structure of ACN ...................................................................................................................... 19

Figure 17 – Tungsten vs LED Dimming. ............................................................................................................ 20

Figure 18- Integrating DMX, Streaming ACN and ACN .................................................................................... 21

Figure 19- Example ACN network traffic .......................................................................................................... 22

Example ACN network traffic: ........................................................................................................................... 22

Appendix 20– The Performance of Various Dimming Resolutions .................................................................. 23

Appendix 21 – Analysis of the 17th & 18th Bit for LED Dimming..................................................................... 24

Bibliography ................................................................................................................................... 25

Standards ............................................................................................................................................................ 26

Forums ................................................................................................................................................................ 28

Marketing Material ............................................................................................................................................. 28

Websites .............................................................................................................................................................. 29

Product Descriptions .......................................................................................................................................... 30

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Introduction

Over the past 5 decades’ entertainment control purposes have advanced dramatically from their humble

beginnings, fuelled by the rise of the live events sector and constant development of new technology. Similar to the

artifice, protocols have adapted through a creative evolution to provide system designers versatility suited to

supporting the high demands of the modern day lighting designer.

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Where it All Began

Lighting rigs grew in the 1960’s, ‘spurred on by the popularity of rock and roll bands’, ‘paired with a hunger for creativity

and the advancement of silicone rectifier dimmers’ (Davies, 2016). A demand for more control was fully realised when a

technological gap was bridged allowing the remote control of dimmers with a modest size console [1]. Soon after

‘Multiple brands began producing equipment to capitalise on the industry’s demand for more accurate control and

dimming’ (Howell, W. 2015). The control method adopted by the majority of manufacturers took inspiration from

technology used for electromechanical position tracking, alarm systems and motor control. (Cadena, 2002).

Early circuitry was fairly simple, based on multiple potential divider/transistor circuits with a common ground,

potentiometer resistance of 10Kohms and minimum source of 2MilliAmperes. The resultant hardware was simple to

repair for anyone with a modest understanding of electronics. (Sourceforge).

The obvious secondary benefit to this technology meant each unbuffered output could be fitted with a blocking diode

(Zener or equivalent), allowing multiple controllers to be connected in parallel to the same dimmers on a ‘Highest Takes

Precedence Basis’ to ‘backup’ consoles.

The beauty of this primitive system was that 1:1 control was achieved, allowing for an infinite refresh rate (Cadena, 2002),

impossible by digital standards. Unfortunately, this meant that if the signal path was cut, the resultant infinite resistance

(V=IR [0v= OFF]) would result in darkness. The prevalent issue raised was a lack of inter-brand compatibly, saturating

the market with over ‘16 different flavours of connector’ (Howell, W. 2004). Most brands appeared to standardise with 8-

pin DIN, although control voltages remained erratic, [2]. This resulted in scenarios such as 28v dimmers linked to

consoles that output 10v@100%, consequently output level would not pass 35% intensity and vici-versa. Across the board

most systems utilized DC control voltages.

Brands initially saw this as a strategic advantage requiring customers to buy into their entire product range instead of

singular items (Gilbert, J, 2016). During the 70s’ a push from the New York rental market to standardise control signals

was felt, following various origin equipment often being put together. Soon after, manufacturers such as Kliegl, &

Colortran and Strand made their products interoperable at 0-10VDC. By the late 70’s following the basic definition of a

protocol, it could be said the first had been put into use (Jands Lighting, 2014).

Disadvantages facing all analogue protocols were volt drop over long distance transmission; resulting in 100% at the

console not relating to 100% at the dimmers, proven by tests carried out by the IEC. [3]. Some manufacturers combated

this using 0-24VAC control, but despite traveling further and being deemed a safe ELV (International Electrotechnical

Commission, iec.ch), it was susceptible to short circuits caused by cable damage whereby signal+ was grounded

prematurely. The nature of the technology made it physically impossible to install the quantity of optical isolators

required for each channel using a 1:1 transformer, let alone justify the expense to protect a cheap potentiometer.

(Mehrdad Taki 2014)

‘E1.3’ (Entertainment Technology- Lighting Control System- 0 to 10V Analog Control Protocol (ANSI), was not officially

recognised until 1998 by ESTA (epanorama.net, 2009). Even after recognition, the defined transceiver resistance ranges

had large scope, encompassing all previous 0-10VDC products that fell into the unofficial standard. The movement

toward bigger rigs and installations demanded an increased level of control whereby analogue outputs ‘capable of

handling -0.5V-15VDC’ (ESTA) were not cost effective and often resulted in thick, expensive, impractical control looms

that often saw ‘ghosting’ of channels, a result of inductance. It became clear a new generation of control was required.

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The Introduction of Multiplexing

It was recognised 0-10VDC control was unsuitable for dimmer-per-circuit systems (R’n’R, 2007). By taking

advantage of microprocessor technology, brands ADB(S20), Century Strand & Strand UK introduced the first

multiplexed control systems in the 1980’s allowing for multiple dimmers to be controlled by single cables linking

receivers in ‘daisy-chain’ formation, (Strand Archive, 2008):

Analogue

AMX 192

Derived from an acronym of AnalogMultipleX and maximum number of controllable channels, AMX192 was

developed to address the significant control problem facing the industry (Schiller, B. 2010). AMX192 relied on a serial

backbone linked through mini TA4 connectors, two cores of which carried a differential clock with its own driver

circuit. The remaining two carried a 0-5V analogue control voltage synchronised to each 50uS clock burst. (Century

Strand, 1972).

The protocol and characteristics of its receivers were standardised by USITT, (USITT, 1985) and enabled up to a 16

channel footprint per receiver (meaning a minimum of 12 could be used to saturate an AMX192 stream).

The ‘mini TA4 connector’ was favoured due to its low price-point in comparison XLR, however its size and fragility

inevitably resulted in companies modifying their stock to accommodate the further robust XLR connector. It was

issues such as this and the fact the specified cabling was un-shielded and susceptible to electro-magnetic

interference (EMI) that lead to it not expanding beyond the USA. (Gilbert, J. 2016).

D54

In the meantime, ‘Strand Lighting’s UK R&D group developed an analogue multiplex designated D54. Originally

developed for use with the Galaxy and Gemini consoles (Strand Archive 1980&1984), it differed from AMX192

featuring an embedded clocking scheme [5] consequently requiring two core cabling and a shield. This quickly

superseded AMX192 with its ability to control 384 channels and a claimed expansion capability of 768 channels,

becoming the UK’s unofficial analogue multiplexing standard. Strand’s early receivers used simple hardware

counters that rolled over before reaching 768, effectively preventing commercial exploitation. In another sense,

this benefited the company, ensuring the signals’ refresh rate was not sacrificed in the pursuit of channels (Schiller,

B. 2010). Strand’s solution to this was to allow each console to support multiple D54 streams. The technique saw

D54 systems installed in theatres up to the mid-1990s (Stage Electrics, 2015).

The connector of choice was the 3pin XLR [4], this negated hardware issues that’d surfaced with AMX192 as well

as being further robust than the previous 8-Pole DIN of 0-10V (E1.3).

Both protocols were simple to troubleshoot as direct voltage levels could be seen on an oscilloscope [6]. Despite

this, tests carried out by professionals, depicted similar voltage drop properties applied as did previously in terms

of send and receive levels being dissimilar once factoring in ‘volt drop’ (Entertainment Design, March 2000).

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Digital

The digital revolution negated volt drop as control signal voltage properties had no bearing on levels transmitted.

(Sandstrom, U. 1997). History repeated itself again as vendors brought their own protocols to market to improve

on the path strand had laid with its analogue multiplex’s (Strand Archive, 2008). During the '80s it became apparent

there were two self-interested factions of the lighting control industry; manufacturers who viewed their installed

equipment as a strategic asset and those who were striving for a more unified industry. (Theatrecraft, 2016) These

protocols included:

Brand Proprietary Digital Protocol

Keigel K96

AVAB A240

NSI Microplex

Colourtran CMX

Electro Controls CEmux

Teatronics Tmux

Contention to lock customers into each brand’s specific protocol grew. As newer products were released protocols

were updated and in some cases even lead to compatibility issues with manufacturers own product lines (Engdahl,

T. 2004).

Despite the paradigm shift within the lighting sector, the quantity of information and high speed control required

by laser technologies made it impossible to replace the one head/DAC system with digital protocols due to

bandwidth restrictions. Consequently, analogue ILDA control (ILDA.com) through the DB45 connector remained

firmly in place [7].

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The Standardisation of DMX512

Equipment owners were again in a position of clamouring for a unified standard. When released, ANSI’s

(E1.11DMX512-1986)’s verbose information satisfied, even to the point of specifying hardware such as ‘Belkin

copper cable’ and ‘120Ohm termination’ (ANSI E1.1) an advancement on E1.3’s ambiguity. (Theatrecraft, 2002).

Similarly, to AMX, DMX stood for DigitalMultipleX, with ‘512’ referencing its channel count. Sent in ‘packets’

containing 513 frames, DMX-512(E1.1) [8] used one to initialise and the rest to transport ‘7-bit’ channel level data.

These shared characteristics with Colourtran’s CMX-156, incorporating simplex communication over pins 2 and 3

for data +&-. whereby the line driver took the form of a console linked to various differential receivers. (Mobsby, N.

2005).

The signal structure is as follows:

Reset

MAB

Start code

Dimmer 1 level

Dimmer 2 level

Dimmer N level

A ‘driver’ isn’t required to transmit all 512 data frames, but a minimum of 24 must be adhered to (DMX512[E1.11]

1986), [9]. Receivers apply iteration when reading packets- (resetting on every initialisation frame) removing the

need of a channel count; consequently, saving 8bits (1byte) per frame and reducing each universe to just 250Kb/s.

Strict timing intervals made DMX512 costly to implement, leading to a slow uptake of the technology. Soon German

competitors produced attractive and cheaper alternatives (Cadena. R, 2010). In reaction ANSI relaxed the timings

forming (ANSI DMX512-1990 E1.1) which quickly became universally accepted. This lead to order, structure,

interoperability and major economic benefit to all sectors of the industry in addition to advancement of intelligent

fixtures and more powerful PC-based control systems utilising RS232->RS485 converters. (Virgo. B 2015).

The uprising of the "interface" sector for analogue to asynchronous serial data, allowed technology to be bridged

and capital costs rescued. A popular device was the DMX512(E1.11) to 0-10VDC(E1.3) converters, allowing newer

consoles to ‘handshake’ with older installed dimmers, (Zero88, 2004).

ESTA was transferred the DMX standard in August1998 where it was officialised as IEC62136 (IEC.ch, 1999) but was

not given international recognition before 2004 in the form of (E1.11) DMX512-A.

This saw the introduction of ‘Alternative Start Codes: ‘reserved ASC’s’ were set aside for commonly occurring tasks

such as lamping fixtures on, whereas ‘proprietary ASC’s’ were registered to carry out certain functions for specific

fixtures as determined by manufacturers. (Mobsby, N, 2005).

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ASC’s include:

Operational Lamp hours

Strike lamp functions

Macros

In keeping with previous updates DMX512-A was fully backward compatible to ensure legacy equipment still

functioned. (Cadena. R, 2010). Improvements included an increased buffer speed of 44Hz to combat latency.

Although the limited 512ch bandwidth and inflexibility of data remained similarly, parity bits were not added to

correct erroneous data over long distances (Carlson, S. 2000). As expected, DMX512-A did not negate the issue of

losing data to everything ‘downstream’ if a component became faulty in daisy chain formation, neither define the

procedure after DMX has been lost for more than one second.

DMX512-A ruled out the use of 3 pin XLR connectors, preventing confusion between lighting and audio cabling,

limited pins ‘4 and 5 to RS485 data only’ (ANSI DMX512-A) to combat manufacturers using them in various, often

dangerous ways.

Space within the protocol was allocated to the development of ‘Remote Device Management Over DMX512

Networks’ (ANSI E1.20) enabling a system referencing only UID’s. RDM was officially released in 2006 [10] and met

with varied response from industry. Originally based on the High End Systems ‘Talkback’ protocol, RDM [10] allows

half-duplex communication and could be described as a language transported by the DMX(E1.11) protocol. DMX

packets start with a null start code of 0x00, whereas RDM starts with a code of 0xCC. The discovery process

identifies and polls each receiver individually for model, make, sensors and channel information. (RDM protocol,

2008). DMX was a designed as a stream not duplex system and RDM effectively bolted on. New hardware is required

to distribute DMX for what is viewed as little benefit in smaller venues. RDM discovery can take up to 30 seconds

over the half duplex system, (Punktech, 2007).

DMX allowed for a range of advanced function topologies:

-Ef1 half duplexed

-Ef2 primary direction send and receive

-Ef3 half-duplex send or receive

-Ef4 half-duplex send or receive (Secondary link pins 4&5 equally duplex)

RDM’s uptake was slow and usually implemented into ‘niche’ companies’ products only. Initially snubbed by

designers claiming ‘addresses would be pre-set prior to rigging’ (Moreau. N, 2014). RDM has the ability to report

operating statistics, error conditions and remote monitoring of entire lighting rigs through each data stream. (LSC

Lighting, 2013). The technology was eventually adopted by larger brands as standard (Robe,2015) and consequently

can be found in most rigs by default, in realisation added benefit could be found in schools, architectural installation

and areas hard to access.

Constant demands ultimately lead to DMX512 being stretched beyond its capabilities.

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TCP/IP and Networking As lighting rigs grew and fixtures occupied more channels, DMX distribution became expensive. The solution came

from the IT sector’s- TCP/IP in the form of two main eDMX protocols: Transport” (e.g. Art-Net) and “Real-time”

(MA-Net2). Both are based on IPv4 with class C IP addresses which made way for ‘Remote Focus Utilities (RFU’s)

that could be connected by means of IEEE 802.11 and used to control certain functions of consoles, (though usually

in limited capacity).

Transport Protocols

Transport protocols package DMX data, place a universe number in front, then send it across a network. This solves

a number of DMX512(E1.11)’s issues such as; a limited bandwidth of 512-slots per universe and how only one

lighting controller was permitted in the system. (Howell 2016, p.5). DMX messages can be readily converted to and

from eDMX messages providing interim technology to integrate DMX devices with Ethernet systems.

Communication takes place between ‘nodes’- (devices converting eDMX to DMX512 data or vici-versa) and ‘servers’

(devices generating control data) (Eclipse, 2014).

As expected the dimmer-per-slot model of DMX512 still doesn’t translate well to intelligent fixtures (Huntingdon.

J, 2012) fixture libraries are still necessary and increasingly complicated. Allowing limited or no talkback from

devices. A suite of protocols dubbed ‘Fixture-Net’ was implemented to allow the transport of bi-directional data

including 600x400 video [CITP] (Werdlund, 2014) and RDM over RDM-Net(E1.33). The discovery speed was increased

due to network transfer speed, although RDM’s more fundamental issues still required addressing.

As ArtNet expanded into media server pixel-mapping, the ‘ArtSync’ packet was introduced to ensure a stable

refresh rate and smoother images Higgins, D 2011). Network latency soon became problematic as ‘broadcast’ data

flooded the entire network, ArtNet-3 introduced a simple algorithm to learn what data was being consumed at each

node then directly unicast (thus a massive reduction in traffic).

The capacity of sACN(E1.31) and Art-Net systems are scalable to the available bandwidth, from 40 universes

(10baseT) to over 4000 (1000baseT Gigabit) with a theoretical software cut-off of 32,768 universes (Protocol Today).

Real-time Protocols

Real-time protocols give live feedback and status of network nodes. Once again proprietary protocols with

encrypted header packets enable brand specific additional features. Most of these products support transport

protocols, but feedback capabilities are eliminated whilst they are in use (Leviton, 2015). These include:

-AVAB -Strand Lighting -MA Lighting

Colourtran -Rosco/ET -ETC

-Compulite -LSC -Pathway Connect

-EDI

Within laser technologies Pangolin’s buyout of Phoenix lead to the development of new hardware. Allowing

interfacing with a control PC over TCP/IP to upload multiple effects as well as real-time monitoring over the CITP

protocol, (Pangolin, 2014) [11].

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The Future

At the time of DMX512-A (ANSI E1.11)’s most recent update ESTA’s board members wouldn’t have been able to

estimate the capability of new fixtures, media servers and rise of LED technology, forcing the one slot per fixture

model to its limits. (Isamu Akasaki).

ACN [16] (ESTA/BSR E1.17, Entertainment Technology - Multipurpose Network Control Protocol Suite’) will unlock

this technology to its full potential instead of the current 256level 44hz rate imposed by DMX512A(E1.11) [17]. At its

core is a very general specification. In many ways, the EPIs supported are almost as important as the core

components themselves.

DMX512 was never intended to do a lot of things. strollers, moving lights or strobes. or express functions such as position or color wheel index or give 100% reliable delivery. (Huntingdon, J. 2012) name. ACN is built from-the-ground-up to communicate with all devices in an entertainment network [13].

Interoperability profiles are designed to grow with technology and are provided in ANSI E1.17 for initial service discovery across a system for:

-Allocation of multicast addresses when used on UDP & IPv4

-UDP port allocation when multicasting is non-specific

-IP address assignment in conformant systems

-Protocol timeouts in specific environments

Other EPIs conforming to the architecture have been developed outside the ANSI E1.17 standards to allow for integration such as; ‘ANSI E1.30-3-2009-Time Reference in ACN Systems Using SNTP and NTP ANSI E1.30-4-2010’ which defines how to use DDL to describe devices using the same Root Layer and PDU format controlled using sACN(E1.17).

ACN is an extensible standard: while it is currently envisaged to run over TCP/IP, UDP/IP and standard IEEE 802.11networks, it has been written allowing it to be transferred to another kind of networking system should it become suitable. ACN was designed to be layered on top of DMP, TCP and SDT. As defined in the initial standard (Jason, 2013). [19].

ACN is supported on Linux ARM, i386, Windows x86-64, Macintosh and PowerPC by the Open Lighting Architecture,

but unlike ArtNet’s constant transfer rate of 5767168 bits/s/universe (Howell, W, 2008), ACN is unpredictable with

traffic that can fluctuate dependant on the lighting state. Using commands instead of levels, ACN lets fixtures carry

out each action to ensure each parameter is controlled in the best possible way (allowing a theoretical infinite

dimming resolution [20]).

ACN’s architecture consists of a number of separate protocol formats, languages, including:

Session Data Transport SDT is a reliable multicast transport protocol operating over UDP/IP which can be used to group ‘peers’ within a

network into ‘sessions’ before delivering individual messages. The reliability mechanism provides online status

allowing components to detect when a connection is broken. SDT provides fine tuning over the trade-off between

latency and reliability [15] (Collaborative, 2014).

Reliable delivery guarantees all messages will be delivered without errors (and in the correct order), but comes

with a large overhead making it unsuitable for ever-changing data requiring low latency.

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Device Management Protocol

The DMP [12] represents devices as a set of addressable properties representative of their state. To avoid the

inefficiencies of polling, DMP provides a subscription mechanism whereby a device will asynchronously send event

messages to all ‘subscribed’ controllers if/when values change (similar to the way tracking currently operates).

SDT provides reliability across the E1.17 standard, but DMP has also been operated using TCP to provide reliable connections. The size in bits, representation, read/write accessibility and function of each property in a DMP device is determined by information provided externally or by description written in DDL [12] (OpenDMX community, 2014).

DMP allows duplex monitoring of elements such as temperature and calibration. Unlike typical ASC’s there is no practical limit to the number of properties each fixture can have. All fixtures will work off their own unique IDs, which will remove the need for addressing(E1.17).

Migrating to ACN

Moving away from DMX based systems seems scary for a large number of people with its channel structure

engrained. ACN can be thought of as a protocol employing forward tracking built solely on unified ASC’s (Wireshark,

2016).

Currently there are too few ACN-capable devices to build a purely ACN system. ACN is incorporated in some

ancillary ports of lighting networks such as ETC’s NET3 systems (ETC, 2008). As ACN can run simultaneously on

the same infrastructure as sACN(E1.31) or ArtNet a gradual device replacement can be facilitated [16]. Eventually

(over a few decades) it is said DMX and DMX-over-Ethernet devices will be decommissioned, and replaced leaving

purely ACN systems (ESTA,2014).

Those who spend money on equipment have always demanded standardisation for long-term solutions. Old

standards produce value for those depending on them every-day; consequently 0-10-volt(E1.3) analogue control, is

still in widespread use. Similarly, DMX512 will not fade away in the face of ACN and other new protocols.

2746 Words

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Appendices

Figure 1 – Davies Black Sabbath 1976

(Image: Black Sabbath 1976 - Davies, C).

Figure 2 – The DIN Connector & E1.3

ESTA E1.3, Entertainment Technology - Lighting Control System - 0 to 10V Analog Control Protocol, Draft 9 June

1997 (CP/97-1003r1)

-0-10v Dimmers must be capable of accepting any voltage between -0.5V and +15V without damage. Voltage higher

than +15V shall cause the device to remain at ‘full on’.

-Receivers have a nominal input impedance of 100±20 kΩ (i.e. maximum 1.0±0.2mW at 10 V) analogue tolerance

shall not be more than +/-20mV(39.9mV).

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-Receiving devices shall use connectors with male contacts. Controllers or sending devices shall use connectors

with female connectors. If suitable connectors are not available in both sexes, the same connector may be used on

dimmers and controllers (typical 8-pin DIN)

-The input impedance of a dimmer or another receiving device shall be a nominal 100KOhms (+/-20%).

Figure 3 – IEC Volt drop Calculations

VD = Voltage drop (conductor temp of 75°C) in volts

L = One-way length of the circuit's feeder (in feet)

R = Resistance factor in ohm/ft

I = Load current (in amperes)

Figure 4 - Century Strands D54 Connectors

Previous 0-10VDC analogue E1.3 DIN connector - The D54 3 pole XLR (Cannon Jack)

E1.3 allowed for both genders to be used as either in or out under certain situations. D54 only used male for

receiving data and female for sending with no exception. Due to this, it was viewed as generally safer.

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Figure 5 – Century Strands D54 Signal Parameters

Electrical Parameters

Parameter Abr. Transmitting Receiving

Max Min Nominal Max Min Nominal

Transmitting Impedance1 Ro 10 Ω - - - - -

Receiving Impedance Ri - - - - 90 kΩ 100 kΩ

Termination per dimmer2 Rt - - - 30 kΩ 20 kΩ 24 kΩ

Termination capacitor3 Ct - - - +25% -25%

Sync Level Vs -6.0 V -4.0 V -5.0 V - - -

Sync Detector Threshold Vst - - - -3.0 V -2.0 V -2.5 V

Full Level4 Vf 5.1 V 4.9 V 5.0 V 5.1 V 4.9 V 5.0 V

Off Level Vo 0.1 V 0.1 V 0.0 V 0.1 V 0.1 V 0.0 V

Safe Input Levels Vm - - - - +/-10 V -

Temporal Parameters

Parameter Abr. Transmitting Receiving

Max Min Nominal Max Min Nominal

End of Frame pulse Te 0.5 s 35 µs - 0.5 s 30 µs -

Inter-Frame period Ti 15 µs 0.5 s - - 10 µs -

Sync Pulse Ts 10 µs 6 µs 8 µs 15 µs 3 µs -

Analogue Valid Delay Tv 15 µs - - 20 µs - -

Analogue Hold period Th Td 50 µs - Td 45 µs -

Total Dimmer period Td 0.5 s 70 µs - 0.5 s 70 µs -

Total Cycle period Tc 0.5 s - 40 ms 0.5 s - 40 ms

Analogue Gate Delay Tg 20 µs 0 - - - -

Number of Dimmers N 384 1 - 768 1 -

Slew Rate - - 2 V/µs 2.5 V/µs - 0 -

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Figure 6 – D54 signal, Oscilloscope Reading

Strand’s D54 analogue protocol structure over a pair of terminated cable.

Figure 7 – ILDA Pinout

Figure 8 – Standard RS485 Configuration

Above diagram depicts a typical RS-485 network. Which allows for multiple receivers per stream. DMX512 cabling

creates a cabling layout as depicted above through the use of shielded twisted pair cable. And physical in and out

ports internal ‘Y-Splitting’ and filtering is carried out within each RS485 Receive device independently.

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Figure 9 - Pulse DMC-8

The Pulse 6 channel DMC-6 outputs 28 frames of DMX512-A level information per packet despite only controlling

6 channels in order to comply with the ANSI Standard.

Figure 10 – RS485 Duplex Communication

RDM (ANSI E1.20 Remote Device Management) requires each receiver to operate and accesses the RS485 network using

both send and receive (see diagram above). Bi directional communication, with up to 32 receivers per stream of the

protocol.

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Figure 11 - Pangolin Flashback 4 – SE

The development of new products such as the Pangolin FB4-SE have allowed for the networking of up to 24 laser

projectors to the same incidence of software. This Dramatically reduces cable cost between each unit and improves

whole show integration by eliminating the requirement for a multitude of expensive DACs at the control position.

This system does not allow for duplex communication from the projector itself due to the physical laser being driven

by a varying analogue voltage through an internal ILDA signal. Despite this each animation can be triggered on

each FB3 and can connect back to the control software through the use of the CITP protocol.

Figure 12 - Typical DMX vs DMP Messages

DMX512 (RS485 simplex) data’s repetitive constant output sends unnecessary data at a uniform rate, well suited to 512

channels but over a much larger number of fixtures the majority of data transfer would be redundant.

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Figure 13 – Typical ACN and Streaming ACN Messages

sACN (ANSI E1.17: The Streaming of DMX512 over ACN) is a transport protocol and allow the streaming of ANSI

E1.1 DMX-512-1990 onward over a TCP/IP network. In comparison. ACN commands are designed to fixtures instead

of repetitive serial messages such as sACN (A non-duplex transport protocol) Transmitting redundant information

-ACN takes the form of HTP from a console.

Figure 14– DDL Communication

Upon first connection each ACN (ANSI E1.17) enabled fixtures will communicate with the console using DDL to inform it of each of its attributes. DDL is an XML based language allowing for a machine parsable description of the interface and capabilities of any device to be defined. This allows ACN to be interpreted by a controller which may then automatically configure itself for controlling specific that devices. The description not only provides the address and property mapping information which is necessary for DMP to operate but it can also contain a huge amount of information on the functionality, capabilities and semantics of the device in an extensible format which allows a controller to extract the features it needs for its specific context while skipping over information which is not relevant to its needs. In normal ACN systems the description for a device may be downloaded from the device itself. Controllers can typically maintain a cache of descriptions for devices they commonly encounter for example fixture profiles could be saved to a consoles internal memory, removing the need for fixture library’s. This removes the need for an allocation cheat-sheet. As seen with DMX. ACN will directly instruct a fixture’s pan to be at 0.00 degrees, without messy DMX mapping that currently goes on.

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Figure 15 – Unreliable and Reliable Messages

ACN breaks down the data being transmitted into both important (critical alert / feedback messages) and semi-

important messages (Parameter levels). By using elements of standard TCP/IP communications ACN is then able

to transmit these messages from console to device using both unreliable and reliable session data transportation.

Unreliable data transmission is a lot faster to process and can be sent with rapidly changing values, e.g. effects,

this is perfect for effect parameter values as a large quantity of data can be processed over a very little time. For

more system critical messages e.g. warnings that require a higher level of error checking which may include

additional ‘parity bits’ for error checking purposes. This method ensures the entire system is as reliable, and robust

as possible.

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Figure 16 – The Structure of ACN

ACN (ANSI: E1.17) is comprised of multiple ‘layers’ containing a number of EPI’s (Interoperability) in addition to

transporting current two way TCP/IP protocols such as CITP.

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Figure 17 – Tungsten vs LED Dimming.

Utilizing commands instead of levels, ACN lets the fixture carry out each action itself in order to ensure each

perimeter is controlled in the best suited way. Due to the nature of tungsten filaments each level set by an 8-bit

dimmer is met with a smooth curve due to heat produced within the filament being directly proportional to light

output. As heat can only be dissipated at a uniform rate from each lamp a natural smoothing effect is created

(much like how a capacitor discharges over an RC transient circuit). The result of this is a natural form of ‘analogue’

fading between each of the 256 voltage levels achieved using an 8 bit dimmer. The result of using 8-bit DMX data

with LED technology is that it looks ‘steppy’; especially the low end of any intensity curve.

In comparison to tungsten, LED’s are not black body radiators and consequently have the ability to react instantly.

Although this is perfect for strobe and snap effects, the semiconductor substrate is not suited to dimming at such

low resolution.

To avoid this, manufacturers of LED retrofit fixtures use capacitors in led emulation fixtures to replicate this effect.

Although this solves the smoothing problem, the led source loses its ability to strobe or ‘snap on’.

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Figure 18- Integrating DMX, Streaming ACN and ACN

An Integrated network structure ensures futureproofing and a smooth transition between each current protocol using

the TCP/IP backbone as well as allowing those of the future to be gradually introduced. This method of integration

benefits all areas of the industry, allowing venues to phase in new equipment over time. Equally this premise is extended

to manufacturers whose development of consoles and fixtures does not have to happen within a fixed timeframe.

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Figure 19- Example ACN network traffic

Example ACN network traffic:

Architecture for Control Networks

Size of preamble: 13

Size of postamble: 0

Packet Identifier: ASC-E1.17

PDU: Root SDT

Flags: 0x70

0... .... = Length: False

.1.. .... = Vector: True

..1. .... = Header: True

...1 .... = Data: True

Length: 64

Protocol ID: SDT Protocol (1)

Component ID: bad00554-bbbb-aaaa-dddd-xyz87654321

PDU: Unreliable Wrapper

Flags: 0x70

0... .... = Length: False

.1.. .... = Vector: True

..1. .... = Header: True

...1 .... = Data: True

Length: 40

STD Vector: Unreliable Wrapper (2)

Channel Number: 42998 (0xa7f3)

Total Sequence Number: 42999 (0x0000a7f3)

Reliable Sequence Number: 42998 (0x0000a7f4)

Oldest Available Wrapper: 42998 (0x0000a7f4)

First Member to ACK: 65535 (0xffff)

Last Member to ACK: 65535 (0xffff)

MAK Threshold: 0 (0x0000)

PDU: SDT Protocol

Flags: 0x70

0... .... = Length: False

.1.. .... = Vector: True

..1. .... = Header: True

...1 .... = Data: True

Length: 17

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Appendix 20– The Performance of Various Dimming Resolutions

From an intensity perspective, LED’s are perfect for strobe effects due to their solid state construction and seemingly

instant response to modulation. Although this attribute is perfect for shock effects and colour mixing, with current control

technology it does not come close to the smooth dimming quality achieved by a traditional tungsten lamp with a slower

response providing natural analogue smoothing between each graduation’. Instead LED fixtures could be described as

‘steppy’ in the low end of the intensity scale.

By incorporating two intensity channels to each fixture in order to give a higher precision 16- bit dimming resolution,

introducing 65535 steps between full intensity and off. Despite this, some people can still identify the stepping effect at

the lower end of the intensity curve for most LED products.

In order to replicate a smooth dimming curve comparable to that of tungsten research has shown that a dimming

resolution of 18 bit or higher is required when using LED technology. This is often only achieved by premium products

with processing internal to the fixture that adds an additional two bits of dimming control. This in turn allows for 4 more

voltage steps to be introduced between each DMX packet and further smooths the light output.

Unfortunately, this makes fixtures utilising this system wait to compare frames before calculating where to place the 4

synthesized bits (shown above). This can lead to discordant transitions if a variety of fixture types are used.

The innovative solution that ACN has to offer to this issue is to tell the fixture to perform a wave form e.g. a ‘square wave’

between two intensities over a fixed time period and allow the dimming resolution to be determined by the fixture itself

with up to 262144 graduations (18 bit) or more. This method improves dimming quality in addition to standardising each

command signals. This results in reduced network latency and a dramatically reduced level of processing for the console

to carry out.

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Appendix 21 – Analysis of the 17th & 18th Bit for LED Dimming

LED Fixtures such as the Robe DL7s Profile (Robe Admin) utilise inbuilt technology to smooth Between 16-bit levels set

by ANSII E1.1 DMX512, each 16-bit increment is read by the fixture and held. This value is then compared against the

following DMX frame and evaluated if level has increased or decreased. After finding the answer to this, the fixture

introduces a further 4 steps (shown in orange) to eliminate sudden drops in intensities across a fade. This system is

incredibly effective for linear fades although is not effective for intensity changes employing the square / inverse square

law. By using ACN (blue), true18 bit control can be achieved with full accuracy to fit any wave type and without any frame

delays due to no data comparisons having to be made. resulting in LED technology being better supported.

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