LED Technology
information about the movements of large volumes of people over time, heat maps of how and when different areas of a building are being used can be created to provide a better understanding of seasonal footfall patterns. This information can also be used to provide location-based services and marketing.
Visible Light Communication (VLC) GPS is the most widely used localisation technology in the world, but it does not work well, or is inaccurate, in indoor spaces. This is because radio frequency (RF) signals like those transmitted from the satellite are obstructed by the indoor boundaries like walls or ceilings of a building. This shortcoming of GPS has resulted in other technologies being adapted to enable indoor location tracking with varying degrees of success. An IPS typically comprises two different elements – beacons and tags. Beacons are placed at different points in a building, while tags are carried by persons or placed on an object whose location is being tracked. Some of the technologies used for location tracking include: ● Inertial Measurement Units: These provide information about the relative movement of a tag using several sensors such as an accelerometer, magnetometer, and gyroscope. An advantage of this technology is that it does not require the use of beacons, but overall accuracy is poor (several metres) because position error accumulates quickly over time. ● Ultrasound: These use sound as the communications medium and operate on the principle of Time of Flight (the time required by sound to travel from a beacon to a tag and vice versa) and can resolve the position to less than one metre but suffer interference from solid objects. This means measurements cannot always be trusted. ● Other RF Technologies: The ready availability of Bluetooth and Wi-Fi makes them appealing for use with IPS but the main difficulty is that these signals vary enormously in how they behave in the presence of obstacles and moving people (due to reflections and multipath propagation). Ultra-wideband (UWB) can penetrate materials such as concrete, glass, and wood, which makes it suitable for use inside buildings (where the line of sight to a beacon is often obstructed as a tag moves around). However, this technology is not yet widely available and power levels at certain signal frequencies are restricted by regulations for radio spectrum usage. The limitations in the use and accuracy
www.cieonline.co.uk
of these approaches mean that they are not ideal for IPS applications. Visible Light Communications (VLC), however, is emerging as a promising solution to the accuracy problem. Visible light is the portion of the electromagnetic spectrum which is perceptible to the human eye (375–780 nm). VLC uses this bandwidth to transmit data wirelessly while simultaneously illuminating an indoor space. In a VLC system, a microcontroller modulates data onto an LED (beacon) and this signal is received by a photodiode in a tag (for example, in the front camera of a mobile phone). Transmitting data using light as a medium requires little if any excess power over and above what is required for the LEDs to provide illumination, and installation costs are minimal because lighting is already present in almost all indoor spaces. While the modulated data inevitably causes the LED light to flicker, the frequencies used are imperceptible to the human eye, but they are easily detected by the receiving devices. By embedding a unique identifier within each LED and modulating this onto the LED driver, each light fitting (commonly referred to as a luminaire) within a building can transmit a unique code associated with its exact location. By using identifiers received from three luminaires, a triangulation algorithm can then determine the position of a tag to an accuracy of 30 cm – an order of magnitude better than the best performing RF-based positioning systems.
Implementing VLC
Efficiency and compact size are the two main challenges when designing a VLC system and the NCL31000 advanced light engine from onsemi addresses both by integrating all the functions needed for such a system into a compact IC. It has a 97 per cent efficient LED driver that supports pulse width modulation dimming and has EMI-compliant DC-DC converters for driving other system components such as sensors. It also has an onboard analogue-to-digital converter (ADC) to provide accurate and detailed diagnostics to a local MCU via a choice of the integrated I2C or SPI buses. A companion device - the NCL31001- supports multi- channel LED applications while yet another IC in this family - the NCP31010 - also integrates a power over ethernet (PoE) driver (in addition to the LED driver) into a single package. This allows data to be modulated directly onto LED light without the need for a separate ethernet driver IC and also allows lighting luminaires to be connected as part of a smart lighting solution. This is especially attractive for designers of smart buildings looking for ways to manage lighting as efficiently as possible. By continuously monitoring room occupancy, lighting levels can be dynamically adapted in response to daily usage patterns. Powering luminaires using DC power supplied through a PoE driver
also eliminates the need for AC cabling and AC/DC transformers in the luminaires, which are also ideally located to house temperature, humidity, air quality and other smart sensors. These ICs are ‘yellow dot’ ready – a luminaire certification programme that allows manufacturers to test and certify that their LED luminaires are interoperable with Philips’ indoor positioning technology and is open to all luminaire manufacturers.
Conclusion
Indoor positioning systems have the potential to provide many benefits for the managers of smart buildings by enabling them to greatly enhance the user experience, safety, and security of visitors to shopping malls, events arenas, airports, and hospitals. GPS is unsuitable for use in indoor applications and as a result, many different technologies have been adapted to provide indoor tracking, with varying degrees of success in terms of the accuracy they provide. VLC overcomes the limitations of other technologies and can be implemented during the design phase of an LED lighting luminaire by using an LED driver IC like the NCL31000. The completed IPS can then be used to track the position of objects and people indoors with an accuracy of 30cm.
www.mouser.com Components in Electronics February 2023 39
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62
