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The Right Protocol - Dr Geoff Archenhold

Issue 60 Apr / May 2011


As Solid-State Lighting continues to displace traditional lamp source solutions in general white lighting applications, choosing the right lighting protocol is becoming ever more important. Dr Geoff Archenhold offers some guidance on intellegent control

When I first started the column nearly 5 years ago most lighting designers couldn’t use LEDs as they were not bright enough for general lighting applications; however, you only need to visit any number of lighting shows to see that LEDs are here to stay as a light source.

Although the efficiency and colour quality is the current focus of the LED industry the lighting design community should start to consider and influence how the future of lighting systems are controlled. It is clear that control systems will enter a new era of sophistication allowing designers to create intelligent lighting schemes that are not only reactive and predictive but also enable self-awareness of users, lighting conditions and a lighting fixtures environment.

I pose the question, why can a light not automatically learn the lighting requirements of the people that sit beneath them? Surely with the computing power available today an LED fixture could determine the age of people and automatically adjust its lighting spectrum accordingly to provide the optimum light for reading, viewing TV or even a romantic cuddle on the sofa. The future of lighting is intelligence and SSL is the tool to forge the future, but how would we communicate with such system?

This month’s column reviews the common lighting communication standards currently available and explores the advantages and disadvantages of each in detail.

Analogue Voltage Control (0 – 10V)
The 0-10V lighting control protocol is determined by the international standard ANSI E1.3 - 2001 and is one of the earliest and simplest electronic lighting control signalling systems. It utilises an analogue voltage input to control the intensity of a light source using a DC voltage that varies between zero and 10 volts. The controlled lighting would scale its output accordingly, so at the highest voltage, the controlled light should be at 100% of its potential output; at 5V, it should be at 50% output; and at 0V it should be 0% output i.e. ‘off’.

The advantages of such a control technique are that it is simple to implement using an external control signal wire and a common return wire. The current used to provide the voltage signal is relatively low (typically 1 to 4 mA), so it can be run along relatively thin cables with little voltage drop.

A further variant of 0-10V dimming control is when the control voltage is provided internally from the LED driver where a remote potentiometer can be connected between two terminals on the LED driver to create 0-10V.

The low voltage control signal means there is no special wiring constraints and therefore lighting fixtures can be connected using standard cabling.

One disadvantage of 0-10V is that as lighting installations become more sophisticated there may be hundreds of networked lighting fixtures and it would require several hundreds of control wires, thereby making diagnoses of problems difficult and increasing installation costs.

A further disadvantage of the Analogue Voltage Control technique include the issue of voltage drop across long control cables which could mean the signal received by the controlled light is not at the same level as the signal that was sent resulting in a reduced or uneven dimming range across fixtures. In addition, analogue voltages are prone to noise and earth loops if not wired properly over long distances.

LED drivers with 0-10V control interfaces are very common; however, the level of dimming is at best limited to perhaps 5% minimum before becoming unstable. The drivers also do not enable any sort of feedback to a network controller and are genuine one-way devices.

Mains Dimmable (Leading Edge or Trailing Edge Dimming)
A common dimming protocol found in both commercial and residential applications is mains dimming which utilises the AC mains cabling to pass power to a light or LED fixture that can be varied by chopping the sinusoidal mains voltages. This dimming protocol is found commonly in the home and is used to provide dimming of incandescent light bulbs. There are two types of dimming protocol variants:
1) Leading Edge Dimming switches: The dimmer switch usually uses a TRIAC for switching on and off and are used with incandescent lamps and mains voltage halogen lamps. The dimming is achieved by cutting the front part of the mains voltage as shown in Figure 1(a) and (b). Dimmer switches that use a TRIAC require a minimum load, typically 10W to 60W to keep the TRIAC ‘on’. This minimum load requirement is not always satisfied by many LED systems when they are dimmed, so caution needs to be taken to determine if leading edge dimmer circuits are properly loaded when installing integrated LED lamps to replace incandescent or halogen lamps. If loading of the dimmer switch is not sufficient then LED lamps will not dim down to low levels adequately and significant flickering may be seen.

2) Trailing Edge Dimming switches: This dimmer switch is popular for use with electronic transformers to dim low-voltage halogen lamps and it means that the trailing edge of the mains voltage is turned off quickly whereas the turn-on voltage is more gradual as shown in Figure 2(a) and (b). The gradual turn-on avoids high inrush currents and the dimmer switch is usually constructed from a FET.

Although mains dimming is popular in the home it is an exceptionally difficult standard to meet by utilising LED fixtures because:
• LEDs do not use significant power and therefore most installed dimmer switches will be rated to work at significantly higher wattages (400 -1000W) causing incompatibility.
• LED drivers may have high inrush currents that could cause issues for the dimmer switches. Therefore it is important to know the inrush current of the LED driver to be used because if 10 LED fixtures are used per dimmer switch then the total inrush current should be multiplied by 10.
• As LED fixtures are dimmed down to low levels their load power reduces meaning that the dimmer switch may not operate correctly resulting in unwanted flickering of the LED lights.
• Most LED drivers do not autosense the type of dimmer switch and therefore the majority of LED drivers available today are trailing edge, so if the LED fixtures are to be used to retrofit it is important to know the type of dimmer switch or replace the dimmer switch at the same time.
• As the mains dimmable LED drivers are designed using a single stage topology there is usually a second harmonic (ie; 2x line frequency) ripple in the LED current and this must be taken into account when looking at the LED lifetime. For example, with a 50Hz mains frequency the frequency of the LED ripple is at 100Hz.The typical ripple peak to peak for mains dimmable drivers is 30% of nominal current or +/-100mA for a 350mA driver.
• The fixture dimming performance is down to the quality of the dimmer switch, so if a low quality switch is used the dimming range may be limited. For example, the same LED fixture could have a minimum dimming range of 20% with a low cost dimmer switch and the same LED fixture could dim down to 1% if a high quality dimming switch is used.
In order to achieve a good dimming performance it is advisable to ask the LED fixture manufacturer for their approved dimmer switch list.
Practically, when dimmer switches are not being replaced but the lamps are being retrofitted with LEDs it is possible to add an artificial load in series with the fixture and that enables most dimmer switches to work even with LED fixtures. Most dimmer switch manufacturers offer these artificial loads which consume approximately 5-20W of power.
An advantage is that many LED fixtures can be connected in series with the dimmer switch enabling a large number of lights to be controlled from a single dimmer switch panel.

Unfortunately, the protocol only offers one way dimming communication and products that are not designed to be mains dimmable will catastrophically fail if placed on a dimming switch mains voltage line.

Digital MultipleX (DMX-512A)
DMX512 is a standard for digital communication networks that are commonly used to control LED lighting fixtures and other devices.
DMX512 employs EIA-485 differential signaling at its physical layer, in conjunction with a variable-size, packet based communication protocol. It is unidirectional and does not include automatic error checking and correction. A DMX512 controller transmits asynchronous serial data at 250 kbaud, so for 512 channels it takes approximately 23 ms to send data, corresponding to a maximum refresh rate of about 44 Hz. For higher refresh rates, packets having fewer than 512 channels can be sent.

The standard has continuosly evolved through subsequent revisions with the latest standard, known officially as ‘Entertainment Technology — USITT DMX512–A — Asynchronous Serial Digital Data Transmission Standard for Controlling Lighting Equipment and Accessories’, being approved by ANSI in November, 2004. This current standard is also known as ‘E1.11, USITT DMX512–A’, or just ‘DMX512-A’, and is maintained by ESTA.

DMX512’s popularity can be attributed to several endearing factors:
• Based upon a standard EIA485 interface
• It is simple to implement
• Very reliable
• Enables control of multiple fixture networks using simple three wire control
• Only low cost components are required
• The control interface is isolated from the fixture and is safe
• Can be used with up to 512 devices (more with additional DMX ports)
A complex network of LED fixtures can be controlled using the DMX protocol which transmits a stream of data between the data transmitter (usually the controller) and a data reciever (usually the lighting fixture). A single DMX port, outputting this stream, can pass magnitude value information for a maximum 512 channels; however, multiple DMX ports can be configured to expand the number of channels available to control additional lighting fixtures.

Therefore, it is possible to control a significantly large number of channels and hence LED fixtures by simply adding additional DMX ports as shown in Table 1.



A typical DMX network is shown in Figure 3 where a DMX512 controller is connected to a network of lighting fixtures in a daisy-chain arrangement. Each lighting fixture has a DMX in and generally a DMX out connector and the DMX out on the controller is linked via a DMX512 cable to the DMX in on the first fixture. A second cable then links the DMX out on the first fixture to the next device, and so on. In general, the final, empty, DMX out connector should have a DMX512 terminating plug attached into it, which is simply a 120Ω resistor joining pins 2 and 3 of the connector; however, many modern fixtures negate this requirement as they are capable of auto-terminating the network.

The IEA485 specification only supports ‘daisy-chain’ networking with up to 32 ‘unit loads’ or fixtures on each network segment which can be up to 1000m. Practically, the use of repeaters or splitters within each network segment should be considered long before cable runs or the number of fixtures limit is reached. It is important to note that a ‘unit load’ could represent a 3 or 4 channel LED driver or indeed a 24 channel LED driver. However, there are several new RS485 IC’s that enable more than 32 devices to be connected to a single DMX port, so for example the Texas Instruments ISO15 RS485 IC enables up to 128 ‘unit loads’ with this IC in to be connected together.

Care has to be taken as some DMX LED drivers claim unlimited numbers of drivers can be connected together on a single DMX port but these do not meet the official standard. Many of these devices use a technique that reads the DMX protocol on its input connector and then regenerates the DMX protocol on its output by using a microprocessor. Such a technique unfortunately creates an accumulative time delay in the DMX protocol between LED drivers, so for a large installation this may be visually seen and if one of the LED drivers develops a fault the rest of the DMX drivers in the chain afterwards would not receive the DMX commands.
The connectors themselves are usually five-pin XLR types; however, within the DMX512-A standard Cat5 RJ45 connectors are also acceptable when used in a permanent lighting installation.

One advantage of DMX is the channels can be easily assigned to a particular lighting fixture providing the functionality of each channels is mapped to the device. For example, the first LED lighting fixture on DMX port 1 in Figure 3 may require 4 channels to individually control a Red, Green, Blue and Amber bank of LEDs. In another instance lighting fixture 2 may just require three channels for R,G,B control whilst LED fixture 3 might require one channel to provide dimming of a white LED fixture.

At the heart of the DMX protocol is the DMX512 packet (shown in figure 4), which contains all of the information required to control fixtures within a DMX network. The ‘Start Code’ within a DMX packet is the first byte of information after the break and is used as a flag to indicate the type of data that follows. A value of ‘0’ indicates that the following frames contain lighting fixture intensity level information. The other 255 codes are not defined in the DMX specification; however, they are utilised within the new Remote Device Management (RDM) standard (see next section) that is based upon DMX.

Each DMX port transmits up to 512 eight-bit channel values, between 0 and 255 and a full DMX packet takes approx. 23 mS to send across the lighting network which corresponds to a refresh rate of about 44 times per second. This refresh rate is generally considered appropriate for the majority of applications and is above the perception rate of the eye.
The only significant disadvantage of the DMX control protocol is that it is uni-directional in nature meaning that the information is transferred one way from the DMX controller to the lighting fixture(s). Therefore, it is impossible to monitor the performance of any lighting fixtures within a DMX network and for example the DMX controller could not monitor whether a lighting fixture had failed.

DMX does not mandate a method of 16-bit encoding for data packets; however, it is possible to use two DMX channel addresses to encode a 16-bit value range providing 65536.

Recently, wireless DMX512 adapters have become popular, especially in architectural lighting installations where cable lengths can be prohibitively long. Although wireless DMX512 networks can function over distances exceeding 3000 ft (1000 m) under ideal conditions, most wireless DMX512 links are limited to a maximum distance of 1000 to 1500 ft (300 to 450 m) to ensure reliable operation. New wireless DMX systems use adaptive frequency hopping and cognitive coexistence, a technique to detect and avoid surrounding wireless networks, to avoid transmitting on occupied frequencies.

However, despite being uni-directional, the DMX protocol has become the de facto standard for LED fixture installation and is now fully understood by most Lighting Designers.

It is clear that for future LED control protocols a bi-direction standard that allows automatic lighting fixture address assignment and performance management will be essential due to the significant advantages that LED fixtures offer the lighting designer and installer.

Bi-directional control protocols
There are a number of bi-directional protocols available for Lighting applications; however, the main ones have been developed into International standards including: Digital Addressable Lighting Interface (DALI); Remote Device Management (RDM) an enhancement to DMX-512A; Architecture for Control Networks (ACN); and KNX. Many of these control protocols have been available for some time but few of them have achieved a dominant position with additional costs involved in implementing them into lighting schemes providing a significant barrier. However, with the advent of LED lighting several are starting to edge in front.

Remote Device Management (RDM)

Remote Device Management is a draft protocol enhancement that will allow bi-directional communication between a lighting or system controller and attached RDM compliant devices over a standard DMX line. This protocol will allow configuration, status monitoring, and management of these devices in such a way that does not disturb the normal operation of standard DMX devices that do not recognise the RDM protocol. RDM provides a significant advantage over competing lighting protocols as it is backwards compatible with DMX devices thus enabling lighting designers, installers, rental companies and manufacturers to continue to utilise the significant investment they have made in LED lighting fixtures so far.

The RDM standard was developed by the ESTA Technical Standards. It uses the time between packets to transmit data to supported devices thus not adding any data that standard DMX devices would consider valid level information. All RDM devices on the link will have a unique identifier (UID) that will consist of a manufacturer ID and serial number; the controlling device can then use a ‘discovery’ procedure to acquire the UIDs of all connected devices and would then be able to communicate automatically to a specific device or in groups identified by manufacturer.

RDM compliant lighting networks offers the following benefits:
• Ability for the console to set the base address of the fixture. This enables rapid installation and no need for installers to set the DMX addresses manually.
• RDM devices can be firmware upgraded via the RS485 cable.
• By allowing bi-directional communication, it will be much easier to mix DMX installations with sophisticated Ethernet protocols such as ACN.
• Control of individual units (individual addressing) or groups (group addressing) is possible.
• A simultaneous control of all units is possible .
• No interference of data communication is to be expected due to the simple data structure.
• Control device status messages (lamp fault, ....), (report options: all / by group / by unit).
• Automatic search of control devices
• Simple formation of groups of lighting fixtures.
• Automatic dimming of all units when selecting a scene.
• System with assigned intelligence (every unit contains amongst other things the following data: individual address, group assignment, lighting scene values, fading time ...)
• Operational tolerances of LEDs can be stored as default values (for example for the purpose of energy savings maximum values can be set).
• Fading: adjustment of dimming speed.
• Identification of unit type.
• Lower system cost and more functions compared to 1–10V systems.
The RDM protocol allows the controller to obtain feedback information such as if the LED light is overheating, operating hours, what the LED current draw is, what the mains or DC voltage is and undertake CCT or CRI measurements in the case of advanced lighting fixtures.
There are several reasons why RDM hasn’t become ubiquitous throughout the lighting industry including:
• The electronics needed to implement RDM was more advanced which added cost to RDM systems. For example, in order to store the sensor values of a fixture EEPROM was required which retained settings after the unit was switched off. Furthermore, in order for RDM units to send information they needed to use a RS485 transceiver rather than just a receiver that was needed for DMX.

• There was a lack of RDM controllers that could actually harness the extra power provided by the RDM complaint devices. The number of limited controllers meant their prices were significantly higher than standard DMX controllers.
• The RDM advantages were not known to the Lighting Design community and they had only become used to DMX standard, so why change.
• There was not many LED drivers that were compliant with RDM, so the choice of manufacturers was limited.
Many of the disadvantages outlined above have now been addressed for example:
• The microprocessors used in DMX drivers have become so powerful they automatically include EEPROM, so there is no or little extra cost to implement RDM.
• Semiconductor companies have implemented isolated RS485 Transceiver solutions that are comparatively priced enabling RDM to be implemented easily.
• The main DMX controller companies such as ENTEC, Artistic Licence and JESE now offer RDM controllers enabling the designers to have full control and easy implementation of installations.
• There are now a wide range of RDM compatible lighting systems available such as ENFIS, IST and EldoLED amongst others.

Judging by the number of products at the RDM compliant corner at the recent PLASA show I believe RDM lighting networks is already starting to become a popular choice with designers and installers. I think the next 18 months may see RDM take over the de facto standard reigns from DMX. This is definitely one standard to keep a close eye on if you’re a lighting designer.

Digital Addressable Lighting Interface (DALI)

DALI was established as a successor for the Analogue Voltage Control (1-10v) protocol and is an open standard as defined by the International Electrotechnical Commission (IEC) 60929, standard for fluorescent lamp ballasts. At the end of 2009 the DALI standard was revised to include extended command functions for a variety of devices including Part 207 for LED modules under IEC 62386.

The DALI communication protocol is designed to operate on a two-wire cable, and the range includes a series of controllers, lamp interface units and special purpose-designed modules, featuring converters and other products to ensure maximum system versatility from a variety of manufacturers including Osram, Philips, Helvar and Tridonic Atco. Using a bi-directional data exchange, a DALI controller can query and set the status of each lighting unit within a DALI network as shown in figure 5.

The advantages of DALI systems include:
• A single bus can control up to 64 devices.
• The ballasts and controls connected to the same DALI bus can be assigned to up to 16 layers (groups or zones) of controls and scenes in the same space.
• A single pair of control wires, which form the bus, connect the ballasts and controls directly, which simplifies wiring in spaces with multiple control zones. The bus is also isolated from each ballast and control.
• Because each ballast is individually addressable, control zones can be established that are as small as a single ballast or light fixture.
• Non-linear dimming down to 0.1% (in theory)

The DALI control bus operates between 11.5 and 20.5V with DALI control bus PSU supplying between 8mA and 250mA maximum.
DALI LED drivers include a microprocessor that functions as storage (ballast address, intensity settings, fade rate), receiver (control signals) and sender (intensity, lamp/ballast status) of digital information. DALI instructions such as GoToScene and SetMax are sent to the ballasts, utilising the data stored in its microchip memory.

Two-way communication enables the lighting system operator to query ballasts for energy usage (using feedback such as IntensitySetting), which can be used for a variety of purposes from energy savings verification to benchmarking to billing internal departments or tenants individually for their lighting usage.

It also enables the operator to query ballasts for lamp and ballast failure (querying for a response such as BadLamp), which can improve the efficiency of lighting maintenance and improve customer service from the facilities department.

The DALI standard requires a dimming range of 100% to 0.1%, utilising a logarithmic dimming curve as shown in Figure 6.  The inverse-square dimming curve is used for better control of the lighting intensity in response to the human perception of brightness and provides excellent visual dimming (no steps at low LED intensity is observed) compared to Linear dimming techniques.

Unfortunately the majority of LED drivers are not able to dim down to this level using DC current with the majority of LED drivers getting to about 5 or 6mA which represents approximately 1.5% on a 350mA driver. Although dimming using PWM is possible this is not favoured for general white light applications as the duty cycle of the PWM signal is so small at the lower dimming levels flicker may be observed unless high PWM frequencies are used. The lowest DC dimming range will soon be available on high quality LED drivers as they are able to reach forward currents of less than 1mA (or 0.3%) with Digital Signal Processing to provide perfect visual dimming.

The control protocol utilises an encoding technique known as Manchester Encoding which provides a degree of error correction; however, the DALI protocol speed is limited to 1200 baud, so is not fast. There is no special wiring required with regard to wiring topology (star, series and mixed networking allowed). The maximum cable length of DALI control wires is 300m for 1.5 mm2 conductors, 100m for 0.5mm2 and 150 meters for 0.75mm2 wires. All devices in a DALI system must comply with the following European standards: EN 55015, EN 61547, EN 61000-3-2 and EN 63000-3-3.

Although DALI has been in the market place for quite some time it has not been widely adopted due to the premium cost attributed to a DALI controlled lighting fixture as compared to a standard (non-DALI) fixture. The cost issue as with the RDM protocol is now being mitigated by the availability of low cost microprocessor and DALI based drivers, so demand for this protocol is once again becoming strong for new projects.

The lighting designer must be aware that not all DALI LED drivers are equal and care must be taken to determine the correct specification of each. For example it will be important to check the minimum dimming range of the DALI driver and also what DALI instructions are implemented within the driver. There are several low cost DALI drivers that do not implement all the DALI commands which can cause issues when being installed with other types of DALI enabled equipment. Always ask your supplier for the DALI instruction set that is implemented with the driver you intend to use (that advice also goes for the RDM protocol).

IP based networks
Today the Internet uses IP protocols as its core communications layer to transfer information between one device and another; however, it is already starting to attract the attention of lighting organisation as a network for communicating with lighting fixtures and controlling more complex devices like video playback servers.
The advantages of using TCP/IP include:
• A low cost infrastructure – Maximum opportunity to use off-the-shelf technology.
• Scalability - Near unlimited lighting networks are possible
• Compatible with Network and Internet protocols so easy to control lighting networks remotely
• Ease of configuration – Networks should be easily configured
• Control protocol speeds are very high (now Gibabyte ethernet)
• Fault tolerance – The system needs to be fault tolerant if packets of information are lost

ESTA is developing a networking protocol called Architecture for Control Networks (E1.17) (ACN) that proposes a way forward for controlling lighting fixtures across IP networks. The protocol is designed to be layered on top of UDP/IP and therefore will run over standard, inexpensive Ethernet and 802.11 (Wi-Fi) network links.

ACN is fully bi-directional; every ACN device will have a unique identifier code, so allowing an ACN controller to ‘discover’ the lighting devices connected to it. However, the intention is that ACN will go far beyond just allowing the console to know that there is a ‘light’ as each light will have a file describing its capabilities that it can send to the lighting controller. This means that even if the lighting controller has never encountered a specific light before it will be able to patch it intelligently and offer the operator control of it in a sensible way.

To provide an easier transition from DMX to ACN, a ‘sub-standard’ of ACN, called DMX-over-ACN, Streaming ACN or, officially, BSR E1.31 lightweight streaming protocol for transport of DMX512 using ACN, has now been created. Streaming ACN is a protocol allowing the familiar repeated ‘channel, level’ information as transmitted by DMX to be sent over a network to suitable receiving devices. In this respect it is very like the existing lighting network standards such as Strand’s Shownet, ETC’s ETCNet2 or the open-standard ArtNet - though, of course, incompatible with all of them!

KNX – Intelligent Buildings

KNX is a standardised (EN 50090, ISO/IEC 14543), OSI-based network communications protocol for intelligent buildings. KNX is the successor to, and convergence of, three previous standards: the European Home Systems Protocol (EHS), BatiBUS, and the European Installation Bus (EIB or Instabus).

The KNX standard is administered by the KNX Association which contains over 200 members with almost 7000 KNX certified product groups in their catalogues. The KNX Association has partnership agreements with more than 30,000 installer companies in 100 countries and more than 60 technical universities as well as over 150 training centres.

KNX was used for the complete lighting controls installation at Terminal 5, Heathrow, the biggest building project in the UK and possibly the largest lighting control installation in Europe.
KNX defines several physical communication medias:
• Twisted pair wiring: This communication medium, twisted pair, bitrate 9600 bits/s, has been taken over from EIB. The EIB and KNX TP1 certified TP1 products will operate and communicate with each other on the same busline.
• Powerline networking: This communication medium, power line, bitrate 1200 bits/s, has also been taken over from EIB. The EIB and KNX PL110 certified products will operate and communicate with each other on the same electrical distribution network.
• Radio: KNX devices supporting this communication medium use radio signals to transmit KNX telegrams. Telegrams are transmitted in the 868 MHz (Short Range Devices) frequency band, with a maximum radiated power of 25mW and bitrate of 16.384 kBit/sec. 
• Ethernet (also known as EIBnet/IP or KNXnet/IP): LAN networks as well as Internet can be used to route or tunnel KNX telegrams.
KNX is designed to be independent of any particular hardware platform. A KNX Device Network can be controlled by anything from an 8-bit microcontroller to a PC, according to the needs of a particular implementation. The most common form of installation is over twisted pair medium.
There are three categories of KNX device:
• A-mode or ‘Automatic mode’ devices automatically configure themselves, and are intended to be sold to and installed by the end user.
• E-mode or ‘Easy mode’ devices require basic training to install. Their behaviour is pre-programmed, but has configuration parameters that need to be tailored to the user’s requirements.
• S-mode or ‘System mode’ devices are used in the creation of bespoke building automation systems. S-mode devices have no default behaviour, and must be programmed and installed by specialist technicians.
KNX has not found its way into the mainstream adoption such as DMX or DALI; however, this may be a standard protocol to watch in the future.

Conclusions

The advent of intelligent LED lighting fixtures is upon the lighting industry and the battle of the control standards will now commence for the lighting protocol of the future. There are several contenders that could easily become the next control protocol standard for LED fixtures; however, it is clear that any control protocol needs to be bi-directional to enable full integration within intelligent buildings of the future. The clear front leaders are RDM and DALI followed by KNX in a distant third; however, the next 2 years will determine the winning control protocol.

Geoff Archenhold is an adviser to the UK Government on LED Technology and helps LED companies raise investment from the finance community. He is an investor in an LED driver company and an LED fixture company, a Lighting Energy Consultancy and euroLEDs Events LLP.


The views expressed in this article are entirely those of Geoff Archenhold and not necessarily those of mondo*arc

 

Figure 1(a) showing Leading edge dimming at 80% and (b) at 20% dimming


  • Figure 2(a) showing Leading edge dimming at 60% and (b) at 20% dimming


  • Figure 3: A typical DMX network controlling three DMX ports each containing a series of LED lighting fixtures


  • Figure 4: A diagram of a typical DMX Packet at the heart of the DMX standard


  • Figure 5: A typical DALI network


  • Figure 6: The non linear dimming down to 0.1% available in the DALI standard

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