Taking Control

David Ogilvy, Technical Engineer at Unios, says that the control system is essentially the brains of the lighting control solution. “It controls the flow of information between components such as graphical displays, touchscreens, buttons, switches, dials, sensors, timeclocks, schedules and light fittings themselves,” he expresses. “All these devices talk via some form of communication interface.”

Logic programmed into the control system performs the smart functionality of the solution. “This can be as simple as activating lights when motion is detected or turning off all lighting when a security system is armed,” explains David. He says that more advanced logic (such as automatically dimming certain lights based on ambient light levels measured by a sensor) is also possible now with most control systems. “The availability of specific features like this is dependent on which control system is chosen.” Besides logic functionality, one of the most significant considerations when choosing a control system is the ability for the system to communicate with end devices. The communication interface between control systems and devices can be one of many different communication protocols - each of these protocols has advantages and disadvantages as they have been designed for specific purposes.

Control systems tend to have one main communication interface which allows the controller to talk to “communication bridges” that then communicate with devices over other specific communication interfaces. David explains that light switches, motion sensors, touchscreen interfaces and other control devices from the same company tend to use the same main communication interface. The availability of these different bridges means that lighting control systems can interface with a wide variety of different lights.” David states that it’s important to choose a lighting control system that supports the same communication interface as your lights.

Once communication has been established with a light fitting, a control system can instruct that light fitting to dim to the desired setting or turn on/off. Modern LED drivers achieve this by adjusting their constant voltage or current output to suit, or by Pulse Width Modulating (PWM) their output.

“Older magnetic ballast fluorescent lighting and incandescent lighting relied on phase-cutting the power to lower the amount of light produced,” reports David. In this legacy environment, phase-cut dimmers were effectively the communication interface and dimming technology in one unit.

David explains that due to its existing install base and the current transition to LED in the retrofit market, phase-cut dimming is one of the most popular methods of dimming LED lighting in the residential market. He further elaborates that LED chips are driven by the LED driver - not directly controlled by the phase-cut power supply. “LED drivers must detect the level of phase-cutting and translate this into a dimmed output level.” Perfect compatibility between all dimmers and drivers is hard to achieve making phase-cut dimmers a less than ideal technology for modern LED solutions.

When it comes to commercial spaces, DALI is the most dominant communication protocol, especially when lights need to be individually controlled. David says that Analogue Dimming (0-10V / 1-10V) and Digital Serial Interface (DSI) are far less common nowadays, but were much more popular before DALI was introduced. “All of these options are wired solutions and require additional cabling on top of regular power cabling.”

Residential installations tend to have lower budgets for cabling and in the case of retrofitting, they have much more restricted access to existing cable pathways. David explains that rotary dial phase-cut dimmers are quite popular in the residential market as they re-use the existing power cabling also to carry a dimming signal. Digital phase-cut dimmers are available that interface with lighting control systems to serve the same purpose. David comments that for this reason, phase-cut dimming has stuck around even as we progress further into the era of LED lighting. Some higher-end smart homes use Analogue Dimming, but it requires the use of compatible LED lights and drivers. “It is much more popular overseas in the US market,” remarks David.

Some common commercial systems in Australia include Clipsal’s C-Bus System and Phillips’ Dynalite which use their own proprietary control bus protocols, C-Bus and DyNet respectively. ABB offers their i-Bus range of products which use the open KNX standard for communication between control devices. “Casambi now offers a wifi and bluetooth based system for installations requiring wireless connectivity,” adds David.

We see that there are also lighting control solutions designed specifically for residential installations, while many commercial systems can be scaled down to suit. David explains that major tech companies have built platforms for automation that include lighting control. “Apple offers the HomeKit platform, Google offers Google Assistant, and Amazon has Alexa.” These platforms rely on third-party products to implement automation tasks, which include lighting control.

For some devices, they can connect directly to wifi and are compatible with one or more of the three major platforms and sometimes with their own platform as well. David explores the most common scenario when it comes to lighting control, which is devices connecting using a more traditional interface with a communication bridge connecting them to a wifi network. “The popular Philips HUE series of smart lights can be connected to Apple HomeKit, Google Assistant or Amazon Alexa through the use of a HUE Bridge.”

When considering a lighting control solution, it’s best to start with the control system. Find one that suits your functionality needs and budgetary requirements. This includes any sensors or physical interfaces like buttons or touch panels. Then make sure the required communication bridges are available to interface with your chosen lights. Finally, ensure the light fittings have drivers with the correct communication interface. Keep in mind that some products are highly integrated and may perform more than one of the core functions.