Intelligent light timers

Time-controlled automation since the beginning of the 20th century

Time can be just as simple when it comes to automation, which first emerged at the beginning of the 20th century with the invention of the timer. It was used to automatically switch street lights on and off, and was therefore already closely linked with the topic of energy. Later, time-controlled automation was also used to reduce heating temperatures overnight. Timers can also be used to charge night storage heaters off-peak, so that they can provide sufficient heat in peak times during the day. 

When motion detectors with passive infrared technology eventually appeared on the scene in the 1980s, time again played an important role right from the start. If this type of motion detector detects movement while there is insufficient ambient brightness, it will switch on the lighting and simultaneously start the switch-off delay time. At the end of the delay, if the detector has not detected any further motion, it switches the light off again. If it does detect new motion in the meantime, it restarts the switch-off delay.

The switch-off delay time can be customised based on the requirements of the location. This applies to both motion and presence detectors. The sole difference is that, while a typical ON/OFF motion detector only measures ambient brightness when it detects movement, a presence detector measures it continuously. A presence detector will deactivate the artificial light if the natural daylight is sufficient to satisfy the required level of brightness, meaning it may even do so if someone is present, i.e. before the end of the switch-off delay time.

Convenient afterglow

From the point of view of energy efficiency, the shortest possible switch-off delay time is naturally advantageous, which will likely influence the parameters in many locations. However, there is another consideration. In many jobs and professions, workers will frequently leave their stations for brief periods throughout the day. If the switch-off delay time has already ended by the time they return, the room will be in darkness, even though a dimmed light would be much more inviting and make the worker feel safer.

That is why the afterglow function was invented. After the end of the switch-off delay time, the light enters a dimmed basic lighting state for a certain period. This means that the person returns to an area that is still slightly illuminated, while the dimmed state means that the afterglow is still more energy efficient than 100 % illuminance. With ESYLUX DALI-2 solutions, the afterglow can be further restricted to specific weekdays and times, since it will generally not be required outside of working hours or at weekends.

Dimmed basic lighting, such as that used for afterglow, can also be helpful in other places, such as passageways. Unlike at a desk, where the purpose of the lighting is to enable the user to work, in passageways the focus is on safety. In typical office corridors in Europe, the minimum illuminance is 100 lux, which is maintained automatically by presence detectors equipped with light sensors. They only switch the lighting off after a switch-off delay time, which is triggered after they no longer detect motion.

Time-controlled orientation light

Similarly to afterglow, this is not always the best solution for the user. If someone is sitting in an office with a glazed door or even glass walls, a slightly illuminated corridor can noticeably increase their feeling of safety. And when there is little or no daylight, anyone moving through or standing in a network of office corridors will similarly feel more at ease if the empty corridors are not in total darkness.

Energy-efficient standby switch-off

Bus systems such as DALI-2 offer a wide range of additional options for improving energy efficiency. The dimming function, for example, also allows for presence and daylight-dependent constant lighting control, which significantly reduces energy consumption compared to presence and daylight-dependent switching. And when it comes to maximising efficiency, a lighting control system with DALI-2 is second to none, particularly in terms of the standby consumption of DALI control gears when the lighting is switched off.

This standby consumption has now been drastically reduced in Europe by the Ecodesign Directive, but it would of course be even better to have no standby consumption at all. Here, once again, we can see the advantage of automation: from a technical point of view, it is certainly feasible to switch off the standby manually when the lighting is not going to be used for a longer period. But how can we be sure that this is actually done every time? That's why automatic standby switch-off is one of the most advanced functions of modern lighting control – for example, outside of weekly operating times, as with the COMPACT APC20.

In addition to fully automatic, semi-automatic and stairwell lighting modes, this is especially true of automatic brightness. It is ideal for use in foyers, for example, where it can automatically provide adequate lighting as soon as daylight or ambient light conditions drop below a certain lux value. To avoid unnecessary energy consumption, this mode should ideally only be active on weekday evenings – which is why the COMPACT APC20 can easily switch to fully automatic mode during the day, at night and at weekends.

These examples show how closely interwoven lighting control and the time factor have always been. And in particular, the example of the DALI-2 industry standard, with its high degree of flexibility, illustrates how more and more possibilities are constantly being developed. And the best part: while the theory of relativity and quantum physics may also continually provide important new insights in the area of energy efficiency, when it comes to lighting control, things are a lot easier to understand. Set the day and time, set the function parameters, et voila!