Osram infrared LEDs establish communication between distributed luminaires
The Australian company Organic Response controls large lighting installations in a way that enables each luminaire to communicate with its immediate neighbors – just like a school of fish would do. Communication is based on modulated infrared light signals that are emitted by high power infrared LEDs from Osram Opto Semiconductors.
Organic Response Lighting Control Systems are designed to operate wide area lighting installations with maximum energy efficiency while still maintaining a high level of comfort. The key lies in a distributed intelligence which enables the system to react to the presence of persons in the immediate vicinity, as well as to those further away. At the heart of the system are sensor nodes integrated in each luminaire. They comprise a motion sensor, an ambient light sensor and an infrared transmitter/receiver pair used for communication.
The moment a sensor node detects occupancy, the luminaire reacts by putting out a predetermined light level. At the same time, it communicates that occupancy to its neighbors by emitting an infrared signal. Subsequently, the neighboring sensor nodes respond by setting their luminaire to a predetermined light level appropriate to an occupant in that vicinity. They then also simultaneously relay another infrared signal to their own neighbors, informing them there is an occupant two light fittings away. Ultimately, each sensor node “knows” how close a person is and sets the luminaire to an appropriate brightness. In this way, it is not just the spot the person is in that is illuminated, but also adjacent areas. This also eliminates the sensation of literally stepping into darkness when entering currently unoccupied spaces. Using light as a means of communication ensures that only luminaires within the person’s field of vision are turned on while systems in neighboring rooms, for instance, will not be triggered. In case an office is reorganized, newly positioned walls will automatically block the infrared signal and thus adapt the system response automatically to any adjustments.
High-power infrared emitter with short switching times
This solution addresses a broad range of applications of different scales and therefore requires high power infrared emitters. The infrared light signal must be set in a way that it reaches all of its immediate neighbors, but does not affect the units beyond. This operating distance first of all depends on the strength of the light signal. But it is also affected by ambient light conditions, the height of the ceiling and the reflectivity of the floor. Therefore, signal strength must be adjusted individually according to environmental and structural conditions. In contrast to lighting installation that require IDs assigned to each luminaire and which therefore need to be programmed, the organic response solution uses the adjustable range of the IR signal to address specific luminaires. It thus eliminates the need for programming during installation.
The infrared (IR) LED Oslon SFH 4725S provides enough optical power to ensure communication for all possible set ups. The IR LED is based on stack technology, which was developed by Osram to provide one chip with two emission centers, thereby doubling its output. Driven at 1 Ampere, the SFH 4725S yields 990 milliwatts of optical power. Its narrow emission angle of ± 45° results in a radiant intensity of 425 mW/sr. The emitted light has a wavelength of 940 nanometers, which is completely invisible to human eyes but a perfect match for the spectral sensitivity of silicon photodetectors. The SFH 4725S features short rise and fall times of 10 and 15 nanoseconds, respectively, and thus permits modulated light signals.