Post Date: 08/22/23
Digital controls promise ease, efficiency and intelligence. Ease in the form of well-designed GUI (Graphic User Interfaces) that make programming groups or controlling individual fixtures simple; efficiency through the implementation of timed scenes or sensor networks that inform fixture behavior and reduce energy consumption; intelligence in the form of real-time and historical data related to fixture performance, efficiency and utilization.
Unfortunately, the reality of dimming implementation often falls short of this promise. System commissioning can be complicated and may require experienced specialists; device coordination can be frustrated by compatibility issues or system limitations; data can be corrupted by external electrical interference. On-going operation can be similarly cumbersome, with end-users unable to manage complex systems, or use them to their greatest effect.
This is only compounded by the array of dimming options and their varying levels of complexity. The goal of this article is to provide a general overview of some of the more common digital control systems in today’s market, and their advantages and disadvantages. Specification of the right control protocol early in the process will provide a great advantage during project implementation and commissioning, as well as lifetime utilization.
DMX (Digital MultipleX)
Over the course of the last 3 – 5 years, we have seen an immense increase in the number of DMX specifications, and in almost all instances, we have seen a variety of issues stemming from its use. The biggest challenge with DMX is that it is probably the most complicated dimming protocol on the market. This is offset by the fact that it is also probably the most robust. Both derive from its heritage in the theater. It has historically been used to provide immensely complex lighting for concerts, stage performances and sporting events.
As a result, DMX is capable of accommodating control of fixture pan, tilt, RGBw color mixing, dimming, fog machines, gobo control, etc., all almost instantaneously due to its incredibly fast data transmission rates, and the assumed DMX user is a highly trained professional. So, if you are exploring DMX, design intent is incredibly important – if you are looking for on/off and brightness control, DMX is probably not the best option, as it will add cost and complexity to your project with limited returns in terms of overall performance. If you are creating dynamic lighting scenes that might require control of individual fixtures or groups of fixtures, or both, with RGBw color mixing, then DMX might be a good option, but it isn’t your only one.
If you decide that DMX is the best control system for your application, our recommendation is that the next step should be hiring a systems integrator with DMX experience to advise on the installation of the system, and to commission it once it has been installed. DMX installation requires special wiring, and if it is not done correctly, the results can be disastrous. Furthermore, many electrical contractors do not have theatrical experience, and will be unfamiliar with the installation of DMX systems. We have seen this first-hand, and in the worst cases, entire projects have needed to be completely rewired because (for example) a contractor used solid wire instead of RS-485 compliant cable.
When considering DMX, there are some very simple basics that need to be followed. First, DMX requires a balanced signal. This is achieved by using two control lines, a positive and a negative. This allows the system to absorb noise, which is cancelled out when the lines are resolved. In order for this system to be effective, DMX requires RS-485 or DMX-certified cable with twisted pairs of wires and a shielded 0V reference signal ground. Using different cable can result in signal degradation caused by environmental noise.
In track installations, even when a third conductor is provided, it cannot function as the 0V signal ground, because in a typical track installation the third conductor is exposed, and not shielded. Recommendations from top DMX control and driver manufacturers and system integrators is to avoid using this third conductor, as it can increase the level of noise in the system, subverting the intention of the 0V signal ground. Furthermore, the linearity of track or BusRun conductors (as opposed to the recommended twisted pair) further degrades signals, a condition that may require more frequent terminations (see below).
DMX512 offers 512 channels of control. You may see some literature that indicates that if you have a simple dim function per fixture, then it is feasible to control 512 fixtures, since each fixture only requires one channel (brightness). While this is technically true, it is also somewhat misleading, because it does not address signal continuity and impedance. The DMX512 standard recommends runs of no more than 32 fixtures, before it is necessary to add a booster or a splitter. EldoLED (which manufactures the drivers that Litelab uses) recommends no more than 25 fixtures, and ETC, who manufactures DMX control systems, recommends no more than 20 fixtures when used with track.
This means that (using ETC’s recommendations) every 20th fixture will need to be terminated with a 120 Ohm resistor placed across the Data+ and Data- control lines. This termination prevents signal reflection that can cause aberrant fixture behavior, and is necessary to maintain signal stability. A signal booster or splitter will then be required to enhance the signal for the next group of fixtures. In track installations, this may take the form of refeeding the track, which means that technically, a DMX track installation will have a maximum fixture capacity of twenty fixtures before being refed. Furthermore, since DMX requires a serial topology, X, T and L legs will need to be coordinated such that the fixtures are in series, and fixture limitations are respected.
The relationship between channels and fixtures is also more complicated than simply assigning one channel to each fixture. For example, depending on performance, a fixture may require more than one channel. An RGBw fixture may require 5 channels for control, one each for fixture designation, Red, Green, Blue and White. Assuming that this is the first fixture in the series, the fixture will use addresses 1 – 5. Since each channel consists of 0 – 255 steps, this means that dimming and color control will have a gradation of 255 settings / channel.
DMX communicates at a 250 kbps baud rate, which means that it has an incredibly fast response time when compared to other dimming systems (like DALI). However, control in a DMX system is unidirectional, originating with the control desk and concluding when the command has been actuated by the fixture. This is an aspect of its heritage as a theatrical system. In order to fulfill the data-recording functions of LEED or WELL, or enable two-way communication with sensors and other devices, you will need an RDM (Remote Device Management system).
To take advantage of the two-way communication of RDM, you will also need DMX/RDM compatible drivers (EldoLED’s drivers are DMX/RDM compatible). One of the additional advantages of an RDM is that addressing is accomplished automatically, otherwise fixtures need to be individually addressed, and channels individually assigned and programmed. While the very high baud rate of DMX facilitates the collection of real-time data, the requirement itself is premised on theatrical applications where immediate tracking of the movements of an actor (for example) might require this type of response time. In other applications, this type of response time isn’t as critical, and the delay incurred by other types of dimming systems is negligible. This is why understanding the use-case of the system is so important – because the advantages of DMX may not justify the added cost and complexity of installation and commissioning, much less ongoing use and maintenance.
Overall, DMX is an incredibly robust protocol, but it does have inherent limitations. An experienced systems integrator should be consulted at the beginning of the process to assist with the layout, design and installation of the system, and it is always best to bring the controls supplier into the conversation early to understand the specific requirements and limitations of their systems. Lastly, it is always recommended that a clear use-case be established early in the process, and that a thorough evaluation of options is completed. Given the design criteria, other protocols (like DALI or wireless) might be advantageous, especially due to the steep learning curve associated with on-going use.
DALI (Digital Addressable Lighting Interface)
DALI was developed as a successor to 0-10v, and is governed by a consortium of manufacturers as an open standard alternative to several proprietary protocols. Unlike DMX, DALI was designed as a bi- or multi-directional communications protocol, and is decentralized. This means that it can assume a number of topologies, including Ring, Star, Tree or Daisy Chain. As a result, managing X, T and L configurations in track does not pose the same difficulties that it does with DMX, and there is no additional RDM required.
Like DMX, DALI allows users to individually address fixtures, and to control fixtures either individually or in groups, or both. DALI2 offers tunable white compatibility, with RGBw certification coming soon, and is backwards compatible with existing DALI installations. DALI control systems can manage up to 64 devices, and the system will automatically assign addresses to the fixtures that it detects. It is also possible to add multiple controllers to a single DALI Bus to increase the number of fixtures managed by the system, making DALI more scalable than other systems, and more adaptable to changes in the fixture or device ecology.
Unlike DMX, DALI does not have special wiring considerations. It is also not polarity sensitive, so there is less of an opportunity to make wiring mistakes that would impact a 0-10v system (for example). It also does not require a shielded 0V signal ground (like DMX does). This means that installation is considerably simpler than other types of control protocols, although it is still recommended that a systems integrator be hired to help commission the system.
Since DALI uses an inherently bi- or multi-directional communications paradigm, it is capable of application with sensor networks and building system management platforms that monitor and record device performance, which is critical for maintenance of sustainability and wellness certifications like LEED and WELL. The introduction of DALI2, D4i and DALI+ also means that DALI can also be used in coordination with wireless systems, either through the use of standardized gateways that enable wired networks to be incorporated into wireless ecosystems, like Zigbee or Bluetooth Mesh, or by allowing DALI to be used over wireless and IP-based networks. The combination of decentralization and wireless compatibility also means that DALI enjoys a degree of future-proofing unavailable to analog systems, and (arguably) DMX.
DALI was developed for large-scale implementation in office, museum and architectural contexts, and enjoys broad support outside of the United States. With increased interest in advanced controls in the United States, DALI is starting to penetrate the U.S. market, and enjoys support from most of the larger U.S.-based controls manufacturers, like Acuity, Lutron, Crestron and ETC. With broader adoption in the United States, DALI is perhaps better situated to accommodate the data and functional requirements of architectural spaces compared to DMX, while DMX is better suited for application in performance, theatrical or sports venues that require faster data-exchange rates and more control channels.
While DALI certification is controlled by the DALI Alliance, DALI itself is an open standard, which means that manufacturers do not need to license it to use it. This can cause issues in instances where manufacturers manipulate the DALI standard, and advertise their product as DALI or DALI compatible. If you are specifying a DALI system, be sure that it carries DALI certification, and includes the appropriate DALI mark. Certification ensures that the system is DALI compliant and compatible. Product that is advertised as DALI, but which does not carry the certification may not have the promised functionality that DALI provides.
Compared to DMX, DALI offers lower installation costs, easier interfaces, future-proofing and compatibility with wireless controls. It is also inherently suited to sensor network integration and data collection, and it provides nuanced fixture control at both the individual and group level. In terms of a wired advanced control system, DALI provides a compelling solution for museum, gallery, office and institutional applications.
Most wireless lighting controls providers offer the same level of nuanced individual or group control that both DALI and DMX offer. They also provide sensor network integration, and the monitoring and recording of data required for LEED and WELL certification. In addition to this, they offer scalable infrastructures with lower installation costs, because they remove the requirement for running data cables (for the most part). Wireless control interfaces are typically app-based and can be downloaded to tablets or smartphones, and they are intuitive and well-designed. Commissioning even a large network can be accomplished by non-professionals, with most wireless providers offering on-line tutorials and training, and automatic device recognition (similar to DALI).
Historical resistance to wireless control in the United States has been predicated on concerns about security. In many instances, these concerns have been ameliorated through long-term application, although understanding device management and access should be a priority when deploying the system. Wireless lighting control systems are either cloud-based or have their own dedicated server, routers and gateways, which means that in either case, the lighting infrastructure is isolated from other building systems.
These two styles for managing wireless signal propagation define the two basic topologies of wireless lighting control; star and mesh. In a system that requires gateways, like Lutron’s Athena, a wireless hub controls a set of fixtures enabled with wireless nodes, with fixture placement determined by the range of transmission and the capacity of the system (the number of fixtures it can control). This is a star topology. If something happens to the node, its constellation of fixtures will be affected. Furthermore, the system of hubs and gateways used to control fixtures will require additional data-cabling (although significantly less than a traditional DALI or DMX installation).
In the BLE (Bluetooth Low Energy) Mesh topology used by Avi-On and Casambi (for example), every luminaire functions as both a node and a hub. This style of organization is nonhierarchical and capable of absorbing loss of a single device without any interruption to adjacent devices. With BLE Mesh networks, there is limited cabling, because each device acts as a hub, and no other gateways or hubs are necessary.
In most instances, the data transmission range of BLE fixtures is more than sufficient for applications in architectural projects. For example, Casambi offers radio transmission ranges of up to 200 meters (650 ft), while Avi-On offers ranges between 18 – 30 meters (60 – 100 ft). Bluetooth-enabled star topologies are more limited in this regard due to the centralized hub, and extension of the system will require the introduction of signal extenders or new gateways as radio ranges are exceeded. Recommended distances for Lutron’s Athena system are within 22 meters (71’) of a Clear Connect Gateway, or within 8 meters (25’) between nodes.
To send and receive signals, wireless systems rely on connectivity, which means that any fixture that is part of the wireless system will require an exposed antenna to receive data. While most wireless controls manufacturers have done their best to limit the size of these antennas, they will have a visual presence. This will vary based on how the luminaire manufacturer integrates the antenna into their fixture design. Furthermore, while there will be cost savings in terms of installation, the wireless antenna and node assemblies can add significant cost to fixtures, and if you are specifying a star-based topology, then you should also account for the cost of additional hubs, extenders or gateways, as well as the labor and materials to wire them.
Most wireless nodes are compatible with 0-10v and DALI, D4i and DALI-2 type 8 drivers, which provide options for tunable white and RGBw color mixing. As a result, contemporary wireless controls systems offer a robust, secure and proven option for advanced digital luminaire control, with few limitations that are not surmountable by the extension of the system or the addition of fixtures / nodes. Like DALI, wireless has enjoyed wide application in Europe, and is currently enjoying increased popularity in the United States as security concerns seem to have subsided with long-term field application.
Advanced controls are here to stay, and their usage will probably increase over time, especially with the popularity of building systems management platforms designed to reduce energy consumption, rationalize space usage and improve the quality of indoor environments. Today, there are two essential formats for advanced digital control, wired and wireless. The former has roots in pre-digital revolution lighting controls environments, with DMX originally developed in the late 1980s for use in theatrical contexts, where fast, reliable and robust control is required, and DALI developed in the mid-1990s for large-scale application in office, cultural and other architectural contexts. The roots and capabilities of both are evidenced in their functionality, as well as the level of expertise required to operate them.
Hesitancy to adopt DALI in the U.S. market is largely premised on a lack of familiarity with DALI products, but many major lighting controls manufacturers are members of the DALI Alliance, and offer DALI products. It is likely that in the near future, DALI will overcome DMX in the U.S. market, in large part due to the technical requirements of the latter, which make it more suitable for use by professionals in theatrical, performance or sporting contexts. Furthermore, of the two, DALI is better equipped to integrate into contemporary wireless networks, with D4i, DALI2 and DALI+ designed for this type of integration while maintaining backward compatibility with existing DALI infrastructures.
DALI’s move to wireless is likely indicative of a broader move in lighting controls to wireless infrastructures. Wireless has many advantages, including scalability, lower installation costs, cloud-based upgrades that can enhance fixture control, seamless integration into device ecologies and the recording and storage of ongoing performance data. The greatest challenge with wireless may be ensuring ongoing compatibility between wireless networks and driver firmware over subsequent software updates, and determining maintenance ownership between luminaire and driver manufacturers and wireless providers when issues arise.
However, based on the success of today's telecommunications providers, these issues are not insurmountable – Apple and Google issue updates to iOS and Android all of the time with little interruption of App ecologies and network connectivity, and both Casambi and Avi-on use the same BLE (Bluetooth Low Energy) technology used in iPhones and Android phones and tablets. So, the standards developed in the telecommunications industry will probably help ensure device compatibility and operability over time. Ideally, as we move passed the early phase of wireless lighting controls, we will see greater standardization, and the DALI mark and standards developed by the DALI Alliance appear to be focused on establishing the groundwork for universal wireless standards in lighting controls.