The earliest lighting controls were simple, single-action switches on the wall of a room that could turn the lights on or off. Multiple switches were then used to control different sets of lights in the same room.

Analogue, then digital, timers were developed to provide basic automation for switching lights on or off. Such timers were often cryptic and cumbersome.

The next advance in automated control was occupant presence detection, which allowed lights to be turned on automatically when someone entered a room. The first presence detectors were passive infra-red (PIR) devices offering the ability to scan small areas of a space or room.

When coupled with internal time-out, the lights could be automatically turned off if no presence was detected for a certain time.

Ultrasonic sensors are the latest step in the continually changing technology used for controlling illumination in the home, workplace and public buildings.

The latest multi-function sensor from lighting management and automation specialist Philips Dynalite combines four detection technologies in the one device. The device adds ultrasonics to the usual combination of PIR, lux level and infra-red technologies. (The last function enables the sensor to be adjusted by a hand-held remote unit).

The new ultrasonic sensor is slightly larger than the company’s earlier devices to accommodate additional components for the ultrasonics sensor.

Philips Dynalite product manager Daniel Walker says that having four sensory disciplines in one device allows the programming of multiple functions.

“Our company is the only one that does this,” Daniel says.

The sensor can be programmed so that when occupancy is first detected the device also determines the natural light level. The sensor can then instruct the lighting controller to supply the necessary illumination from light fittings in the area.

All this happens in a less than a second and removes the need for multiple sensors to be mounted in a room to perform the different functions.

Ultrasonic sensors actively propagate high-frequency waves that reflect off surfaces and objects. The waves are of such a high pitch that not even dogs can hear them. The sensor records reflection back to the device as the reference point, and any change in reflection indicates positive motion detection. The lighting management system responds accordingly.

The main benefit is that the waves can wrap around corners and bounce down into office cubicles. This solves the problem of people becoming invisible to PIR sensors when they are not in direct line of sight.

“Ultrasonic sensors were installed in an office changing room,” Daniel says. “We found that the standing wave was bounced off different surfaces and spread out. We were able to use just one sensor to control all the lights in the change, shower and lobby areas – not three as would be required with conventional PIR occupancy sensors.”

Such an arrangement provides better occupancy sensing performance. Real cost savings in installation and commissioning mean a faster pay-back for the end user.

Different levels of ultrasonic sensitivity can be set. Daniel says some reports indicate that when the sensitivity of an ultrasonic sensor is set to the highest level, it can detect someone’s chest moving as they breathe.

The new sensors are all fully networkable, so they can be linked with other sensors and load control devices, making this a system solution with almost infinite scalability possibilities.

Being digitally addressable on the Dynet network allows the devices to be remotely configured by the control computer. This removes the need to manually adjust switches and potentiometers directly on the device itself, as is required with other solutions.

Ultrasonic sensors have a much larger scanning range, so fewer units are needed on the ceiling. Minimising the number of sensors improves the appearance of a space – keeping architects happy – and cuts the cost of installation and commissioning.

Project savings for a building can be up to 55%, and 15-20% can be saved on hardware and installation alone.

Ultrasonic technology is a big improvement in occupancy detection in a building. As technology advances, the size of the sensors will decrease and their sophistication will increase, allowing even greater integration with the control of other building services.

Staff in office buildings will be better able to focus on their job, and productivity will improve.

Philips Dynalite
http://dynalite-online.com