Wireless Sensor Networks (WSN)—a Key Technology for Smart Building IoT

Industry has been using various types of sensors for a long time, but the Internet of Things (IoT) has taken the use of sensors to a whole new level. Today, wireless sensor networks (WSN) are used in a wide range of applications including healthcare vital signs monitoring, manufacturing defect monitoring, traffic monitoring, and more. In fact, some consider WSNs to be the most critical technology advancement of the 21^st century.

The ‘wireless’ in ‘wireless sensor network’ refers to the type of network technology used to transmit data, containing signals captured from sensor nodes, from one device to another. A wireless network can be based on Zigbee, Bluetooth, or WiFi as examples. Wireless sensors transmit data via radio signals (i.e., over-the-air, using antennas at the transmitters and receivers) whereas wired sensors rely on physical cables or wires to transmit data.

WSN Key Characteristics

• Sensor nodes detect physical phenomena such as light, temperature, humidity and occupancy. A sensor connected to a wireless network sends data to a network manager to then process and generate commands to lights, HVAC, and other building systems.
• Wireless connectivity technology such as Zigbee, Bluetooth or WiFi, is standardized technology that enables a sensor to transmit or receive information, through radio waves, from/to other devices that also use the same wireless connectivity technology. It encompasses both hardware and software, and different wireless connectivity technologies leverage different networking topologies (i.e., mesh, star, bus, ring or tree). For example, a network based on Zigbee standards leverages a mesh topology. In a mesh topology, each sensor node can connect to multiple nodes in the system and pass data through the most reliable path available, which could change over time.
• A Network Manager controls and manages network resources and configurations, and is the connection point between the sensors on the network and the Cloud. It processes data and transfers/receives data of value to/from the Cloud.
• A Cloud Platform is a set of internet-based hardware and software resources that can be used to store, compute, and manage data thus enabling system analysis, centralized optimization, and providing data insights.

Smart Lighting and Wireless Sensor Networks

Commercial real estate organizations need real-time monitoring of their space to enhance the level of efficiency, improve cost-savings and increase occupant comfort levels. Wireless sensor networks are an integral part of a wireless smart lighting system. They are key for improving energy efficiency in buildings and leveraging smart building applications as they closely monitor the environment (light, temperature, etc.) and the activity of the occupants.

Fixture-integrated sensor nodes on the wireless lighting system network collect physical and environmental data in a space including light, temperature and occupant activity. They execute simple commands sent from the network manager such as on/off and dimming. Sensor nodes are densely deployed over the network so that decisions are made based on data collected from multiple sensors, which improves reliability. The lighting system manager collects and processes the data which is then sent to the Cloud where it is stored for easy access by workplace analytics software developers. Using an API, analytics software, developed for specific smart building applications such as space optimization, digital wayfinding and asset tracking, delivers actionable insights that target business improvements such as greater efficiency, better occupant comfort levels, and more.

Powering a Wireless Sensor on a Lighting Network

Wireless sensors communicate wirelessly but still require a power source to actually work. There are several power options that can be considered: batteries or a wired connection to power. 

Batteries - Batteries power most ‘wireless’ sensors, but the usability of the sensor is subject to the lifespan of the battery. Once the battery is depleted, it must be manually swapped out for a new battery or the sensor is useless.

LED Driver Aux DC Output - Fixture-integrated wireless sensors can access power via the auxiliary DC output or ‘Aux’ on the fixture’s LED driver, eliminating the need for batteries. This power option is like using an endless battery or connecting permanently to a DC adapter. LED drivers with this feature offer the flexibility of powering a wireless sensor or controls module and creating a ‘smart’ fixture.  

The Aux can also be used to power a fan to lower the temperature in the fixture. If the LED driver does not have the Aux feature, an additional power pack is required which adds complexity and cost to the fixture-integrated solution. Most OPTOTRONIC® LED Drivers have an Aux feature.

LED Driver with DEXAL Port - DEXAL™ (Data Exchange for Advanced Lighting) Technology, is a non-proprietary, intra-luminaire interface that enables bi-directional communications between an OPTOTRONIC LED Driver with DEXAL Technology and the fixture integrated Connected Lighting Module (CLM) with DEXAL Technology or SensiLUM™ Wireless Integrated Sensor. The DEXAL interface port on the OPTOTRONICS Driver also supplies power to either of these fixture-integrated components.  

The DEXAL interface is ideal for smart building applications that require exact (not estimated) luminaire-specific data including power consumption, temperature profile, operating hours and diagnostics.