Intelligent lighting at the service of indoor geolocation

By combining ethernet diet (POE) and communication technologies by visible light (VLC) of the LI-Fi type, it is possible to create intelligent lighting systems capable, among other things, to locate people inside peopleor mobile industrial equipment (AGV) with a precision of less than 30 cm.

By Mike Sandyck, Onsemi Product Marketing Director, article adapted by Pascal Coutance

Mike Sandyck, Marketing Director of ONSEMI products - Credit: ONSEMI

Thanks to its ability to provide more than 90 W safe and efficiently, ethernet diet (Poe, Power Over Ethernet) has been proved to be one of the main growth engines for connected lighting systems.The combination of this technology with the advantages of visible light communication (VLC, for visible Light Communication), of which LI-FI (Light-Fidelity) is an example, makes it possible to develop extremely safe indoor location systems andefficient, which offer performance higher than that of RF solutions in certain areas of application.In this article, we will see how POE technology has evolved to become a viable solution for industrial lighting, and how VLC technology can be added to the system to allow location.

Update on the POE standard (IEEE 802.3xx)

The POE standard has been developed to allow low -power peripherals to be supplied from a simple central hub, thus eliminating the complexity, cost and compliance problems associated with the mains supply within abuilding.Like many standards, the IEEE 802 standard.3xx - The other name of the POE - has evolved over the years, offering more features and supported power, with each new version.The first version of the standard (IEEE 802.3AF) was launched in 2003 and provides a power of 15.4 W to devices such as IP phones, access points and sensors.In practice, given the losses in the cables, the power available for each device is around 13 W.The following declination of the standard (IEEE 802.3at), also called Poe+, offers a capacity of 30 W, reduced to 25 W still taking into account the losses.Enough to supply more complex devices and load small devices like tablets.

Figure 1 - Different versions of the POE standard and wiring types used - Credit: ONSEMI

If these two standards remain valid, the last version of the POE standard to date bears the name of IEEE 802.3BT.Launched in 2018, it is divided into two categories: type 3 (Poe ++), which can provide up to 60 W per port, and type 4 (higher power poe) which can provide up to 90 W at point D'use.The table in Figure 1 sums up the characteristics as well as the wiring used for the different versions of the POE standard.While the power defined by standard 802.3BT type 4 était destinée à des appareils tels que des ordinateurs portables, avec l’avènement de l’éclairage Led, elle permet aussi d’alimenter des systèmes d’éclairage intelligents de taille moyenne à grande via PoE.

POE lighting systems and visible light communication (VLC)

Poe lighting has many advantages, the two main ones are safety and flexibility.As the voltage of the POE bus remains, by design, below the safety threshold of 60 V continuous, the characteristic risks of the mains voltage, such as electrocution and fire, are excluded from the system.The only necessary wiring is that of lighting;The same CAT 5 Ethernet cable is enough for power and data.This avoids the recourse (and therefore the cost and the complexity) to a mains supply, including the connection of wall switches.

Thanks to the Ethernet connection, the control aspect of the lighting system can be configured via the local network, which offers a range of much wider control options.Integrated sensors can provide information back on the occupation of the various offices or rooms, in order to optimize energy consumption, as well as on temperature control and indoor air quality.Wall switches can evolve towards a low thickness design, wireless and energy recovery, which avoids using batteries or electrical connections and allows you to easily and quickly reconfigure building spaces.

Location systems based on VLC communications

Although it is not a new technology, since it dates back to the 1880s, when Alexander Graham Bell developed its "photophone", which made it possible to transmit data flows using visible lightAs a support, VLC technology arouses growing interest, especially for indoor applications.An obvious application of VLC technology is networking through light (LI-FI), particularly useful in dangerous areas where there is a risk of explosion, or in areas where equipment sensitive to interference are presentradio, as in hospitals or on board planes.

VLC location systems use the lighting sources of a building and a triangulation algorithm to calculate the position of a person or a mobile robot.Credit: onsemi

Another less obvious application is to use light for location systems inside buildings, for example to guide an AGV type vehicle (automatic guide vehicle) in a smart warehouse or factory, or forHelp people sail in large buildings, such as airports, stages or hospitals.This location technology also opens up commercial opportunities such as geolocated marketing, which consists in attracting consumer attention to a special offer present nearby.

Localization systems based on VLC communications respond to several problems posed by GPS indoors.It is possible that the GPS signal does not penetrate very well into the building and, even if it succeeds, bouncing on the walls, the propagation by multiple journeys leads to imprecisions in the system.VLC positioning systems use lighting systems in a building to create a positioning system inside.To do this, each light has its own, unique identifier, which is coded and permanently transmitted by modulating the light emitted at an imperceptible frequency for the human eye.When a smartphone or an equivalent device equipped with a camera and a triangulation algorithm is within reach of at least three VLC lights, the application can then calculate the distance from the smartphone to the three identified light sources and deduceSmartphone position with precision less than 30 cm, as illustrated by the photo above.

POE VLC Systems Design

Energy efficiency and compactness are the two main challenges faced by POE -based VLC systems designers, not to mention the pressure to quickly launch conceptions on the market.ONSEMI benefits from a great experience in the design of high -energy solutions for many applications, including smart lighting.Its smart lighting solution based on Poe combines several very integrated devices in a compact format which greatly facilitates the design.The diagram of Figure 2 illustrates the architecture of such a system.

The intelligent lighting solution based on onsemi POE combines several very integrated devices in a compact format which greatly facilitates the design.Credit: onsemi

The NCP1095 and NCP1096 are POE-PD interface controllers which guarantee the lighting solution to comply with IEEE 802 standards.3af/at et -3BT.They integrate all the functions of a POE system, in particular the detection, classification and limitation of the call current.The NCP1095 and NCP1096 both support applications up to 90 W and incorporate protection against overcurrent and overheating, thus protecting the device and the load of lighting.The NCP1095 uses an external passage transistor for more flexibility in terms of design, while the NCP1096 is a completely integrated solution.

The interface controller is accompanied by the NCL31000 LED pilot of ONSEMI which includes all the elements necessary for a high -performance high -performance lighting system.The key to this device lies in the use of a BUCK LED pilot with a yield of 97%, which supports the wide -band analog variation and the PWM modulation (modulation of pulse width) of the current, until'to a zero current.The device incorporates DC-DC converters to supply the microcontroller and sensor type devices, which avoids using DC-DC converters.This simplifies the design while allowing room for space and reducing nomenclature costs.

Its ability to vary the current with an accuracy of 0.1% as well as its high -level linearity make NCL31000 a tool well suited to VLC applications, including the location based on light.A high and stable reference allows a real variation to a zero LED current, and eliminates any risk of ghost light.The diagnostic functions are very complete, with in particular the precise measurement of currents, voltages and temperatures, which are provided at the microcontroller of the system via an I2C / SPI interface.

As we can see here, with the convergence of low -consumption intelligent lighting made possible by LED technology, and the permanent evolution of the POE standard which allows you to route to 90 W today to the point of use, it is now possible to create sophisticated lighting systems that do not require significant (and expensive) sector wiring.If these systems can be used everywhere, they are particularly useful in dangerous areas such as mines and oil or gas platforms, environments with high humidity, as well as proximity to sensitive equipment, as in hospitals or on boardplanes.

Based on a long experience in the area of power solutions and high-performance LED pilots, the POE-PD1095 and NCP1096 PO-PC interface controllers, as well as the NCL31000 LED pilot Facilitates the design of suchlighting systems, by offering a proven solution, very effective from an energy and fully integrated point of view, which allows faster placing of intelligent lighting solutions.

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