The Last Inch: Why Does the Lighting Industry Still Struggle with Dimming Compatibility?

by | Mar 8, 2021 | News

Modern lighting control and dimming systems can cover tens of thousands of square feet and control equally vast numbers of lighting fixtures, or as the saying goes, “the first mile”. However, each of those thousands of fixtures are now end points, or “the last inch”, which can easily jeopardize even the best lighting designs due to unpredictable performance with the lighting controls. Most of the technical difficulties of a making lighting product operate correctly with a dimming control have been resolved. With the development of advanced electronics and clever interfaces, combined with thousands of hours spent testing product and resolving field problems, the technology required to effectively dim and control almost all modern LED lighting exists.

Despite all the above, the industry remains stymied by how to effectively match the dimmer style necessary to control the LED driver used in a given lighting fixture. This lack of compatibility between dimmer and driver creates visibly obvious, unwanted, and often surprising effects like strobing, pulsing, fluttering, popping (jumping to a bright or dim state), ghosting (not turning off completely), blanking (not turning on) and sticking (only full-on or dimming only to a random level). Even worse, some combinations of dimmer and driver show several of these glitches at various set points. For example, some dimmer/driver interactions will pop on only when set to 100%, strobe while dimming between 100%-50%, stick at the same brightness between 50%1% and then ghost when set to 0%. Some even pulse when set to 0% with a rhythmic electronic heartbeat, while some do all the above for about 10 seconds and then abruptly fizzle out the driver, the dimmer or both. The “magic smoke” packed into those little black boxes escapes forever.

When these glaring problems surface on any project, usually widespread panic ensues. A flood of phone calls, texts and emails are exchanged between the contractor, the design team, and the manufacturers of both the lighting and the dimming control systems. Often the manufacturers of the lighting products do not make the driver, and the lighting and control products are from unrelated companies. The mayhem created drains time, money, and reputations quickly. Sometimes a quick fix is found, sometimes a compromise in settings masks the problem, but most often demands are made to change-out suspect fixture types or the dimming controls entirely. Fingers are pointed, change orders are issued, and bucks are passed. Often, the mystery of the malfunction remains shrouded in technical jargon and gobbledygook. The mess left behind is a massive distraction for the project itself and the entire project team.

Photo Credit:  Jason O’Rear Photography

The question is WHY? How can this industry be stuck on this problem?

The answers: a lack of standards and a lack of information.

Criticism about a lack of standards typically targets the dimming control system, and some of the time, the driver. As mentioned above, these two key components are usually not from the same manufacturer in day-to-day projects. There are several reputable companies who have developed both sides of the equation, using either proprietary systems or modified open protocols to provide an overall better chance of success. However, many technical and commercial barriers prevent one or even both pieces from coming together on a project. A significant issue is NOT the compatibility between the driver and the controls, rather it’s whether the available drivers will work the LED arrays used in each fixture type on a project. Even with a broad portfolio of specialty drivers, the chances of having everything work natively on the dimming control system are slim. Some fixture types, usually ‘decorative’, ‘custom’ or other specialty products like LED tape, are designed with LED arrays that use a specific driver or with driver components integral to the LED array. Many of these designs are intended for installation direct to AC power, tested to dim only with wall-box “phase-cut” dimmers, not to a system. Some may not be designed to dim at all!

This challenge is not limited to this “phase cut” technology like the original solid-state dimmer introduced in the 1960’s, several of which still work well with lighting fixtures have a two-wire line voltage dimmable LED driver. Weird glitches and poor performance happen even when using the venerable 0-10V analog signals, or when using more advanced digital systems. These modern systems include wired protocols like DALI or DMX, and newer wireless systems using Zigbee, Bluetooth or Wi-Fi and possibly combinations of them. While this article does not define these terms, the Illuminating Engineering Society (IES) does in their recently published ANSI/ IES LP-6-20: Lighting Control Systems – Properties, Selection and Specification, which has section on Open Control Protocols. Full disclosure, I am a co-chair of the IES Lighting Control Systems Committee.

Incredible progress has been made on the technology of dimming and control; many drivers and the control work well together, and the technology may also be standards based, but there are still no guarantees that every fixture type will perform as expected. Add in the recent trend of using color-temperature tuning arrays (CCT/white spectrum), and the continued trend towards smaller and smaller profile fixtures with onboard drivers, and the chances of getting everything to work together is nearly impossible.

Next, consider the second gap stated above: a lack of information. Considering the complexity of the information above, how could the lighting specifier know, for certain, that the lighting fixture specified can be dimmed or controlled using one system or another?

Compliments of Casambi

Even with great technology, a vast amount of testing and an obscene amount of money spent developing lighting control products, the problems persist because the information is simply not available or not published clearly. For example, different manufacturers have their own style of publishing information, usually on spec sheets, and each also can indicate their model numbering for options differently. Specifying a standard 0-10V dimming driver may be simply “D” on one fixture, but “010” on another. Note that very few of these designations match from company to company, and not even from brand to brand within the same company. The level of detail provided about the driver or the LED array is highly variable, or there may be no information at all. If the driver uses a protocol, such as DALI (Digital Addressable Lighting Interface), what exactly is supplied? In some cases, there might be two drivers instead of one, which cuts the number of fixtures on a wiring plan in half.

Building on the more recent technology example in the last section, using CCT tuning fixtures requires additional details – for instance, defining how the intensity controlled separately from the CCT range is critical to pairing the lighting up to the controls needed. Perhaps in this example, the driver/CCT LED array uses two separate 0-10V dimming lines, so any control system specified to control it must have an interface capable of managing two 0-10V dimming lines separately, hopefully without doubling the overall number of control devices needed. Next, consider how providing a multi-name specification or reviewing alternate proposals could become exponentially more complex when the level of information provided for each piece of the system is highly variable.

Photo Credit:  designing lighting

Closing the gaps: Last year, the IES Lighting Control Systems Committee published a new ANSI/IES standard, ANSI/IES RP-42-20: Dimming and Control Method Designations, intended to provide a model for both specifiers and manufacturers to move towards standardized information. The standard offers symbols, nomenclature and descriptions that can more clearly define what the lighting and control systems offer. It also prompts the specifier to indicate how a particular fixture type will be controlled, whether switched or dimmed, and which control protocol will be used when more than one are onboard. While this new standard is a great start, it is the community that must actually take action to improve. Specifiers need to insist that manufacturers provide detailed information on the control capabilities of the lighting using the tools in RP-42-20. Likewise, manufacturers need to proactively provide these details, and adhere to the designations and formats in the standard. The goal of the authors of RP-42-20, comprised of people from both the design and product communities, is to help push the industry toward solving that remaining, stubborn detail, of what is actually happening at the “last inch” of the system.

This article originally appeared in the February issue of designing lighting