Level sensors in LoRaWAN technology optimise the logistics of circulating containers that transport raw materials between manufacturers and consumers. The low-power wide-area technology used saves energy and enables users to operate a private wireless network on-site.
There is not a logistics manager who has not always dreamed of containers that independently report when they need to be refilled. Autonomous level sensors and new wireless technologies that can be operated privately on a company’s premises now finally fulfill this wish.
Mobile Containers Report Independently
In the Internet of Things, objects that did not have their own voice before get a chance to “speak.” Today, battery-powered sensors can capture vital data about the location and current fill level of mobile containers, tanks, and silo containers and provide the supply logistics chain with this information. One example of this is mobile silos that transport plastic granules from the manufacturer to the processing injection molding company. At the injection molding site, the granulate is gradually removed and the empty container is sent back to the granulate manufacturer. In such a circulation system, hourly information about the location and fill level of the silo is especially valuable because it can prevent the supply chain from being broken in the case of doubt.
LPWAN Enables Energy-Saving, Wireless Transmission of Sensor Signals
In the application described above, the sensor becomes the intelligent control unit of the silo tank. In this mobile system, the sensor must be able to manage without an external energy supply. This gives rise to a demand to use the available energy as efficiently as possible to achieve the longest battery life possible. Low-power wide area network (LPWAN) technologies are a good solution for meeting these requirements. They ensure low energy consumption with a long detection range for radio signals and enable sensors to transmit data with a battery for several years and over many kilometers. In addition to the energy and detection range parameters, a distinction can be made between SIM-based and SIM-free LPWAN technologies. In SIM-based technologies, a mobile service provider provides a public wireless network. SIM-less wireless technologies can also be set up and operated privately. Such private wireless networks offer the company independence from the network provider and better cost control over the long term.
LoRaWAN for a Private Wireless Network
LPWAN technology particularly well-suited for establishing a private enterprise network is LoRaWAN—a Long Range Wide Area Network. These sub-gigahertz bands allow LoRaWAN technology to achieve very long detection ranges with good coverage in buildings. As such, LoRa signals can easily be transmitted from the basement of a building. In open spaces, they bridge distances of 15 km to 40 km and are therefore equally suitable for indoor and outdoor applications. The LoRa field device sends its signals to a LoRa gateway, which in turn forwards them to a network server. A particular advantage of LoRaWAN technology is that the field devices do not log on to the gateway but only to the network server behind it. Therefore, gateways operate only as converters between the wireless and the wired world. This special system architecture makes the wireless system more rugged, as the data of a field device is simultaneously received via several gateways or channels and forwarded to the network server. Only the server decides on which specific data path it will use for signal evaluation. This procedure not only ensures valuable redundancy in signal transmission, but also facilitates network setup. This means that if the reception quality is insufficient, the network can easily be compressed via other gateways without having to create a new network plan to check the radio coverage. Furthermore, the wireless system requires only a few gateways, as a gateway can communicate with around 2000 field devices at the same time and illuminate an area of 5 to 7 square kilometers.
Regarding data security, LoRaWAN offers end-to-end encryption of the sensor data as it travels from the field device to the internet server. The data can be transferred directly to the processing goods management system.
WILSEN Speaks LoRa
The advantages offered by LoRaWAN convinced Pepperl+Fuchs to integrate this technology into the WILSEN.sonic.level battery-operated wireless fill level sensor. This sensor measures the distance to the filling material using ultrasound and calculates a fill level for the container. The payload to the network server contains not only the distance and fill level, but also the GPS coordinates, as well as the temperature and condition of the battery. In the sensor, the times for data transmission can be set within certain limits. These limits range from once per minute to once per day. More frequent transmissions affect the battery life, but enable the exact movement profile of a mobile container to be determined. Longer transmission intervals with just a few transmissions per day extend battery life by several years.
Wireless Sensor Optimises the Logistics Process
With the current fill level and geoposition, WILSEN.sonic.level operates as an intelligent component to offer a silo tank important information for replenishment logistics. After the filling process at the site of the granulate manufacturer, the silo can confirm the exact filling quantity in the purchase order and authorise its collection at the site of the logistics company. The driver will be notified of the exact pick-up location. The movement profile along the transport route enables the injection molding company to calculate the exact time of delivery. Once the silo has been unloaded by the logistics service provider, the silo will automatically inform the injection molding company’s intralogistics system which ramp it is on. From this point on, the intralogistics system always knows the exact location of the silo on the site, even if it has been put into and removed from storage several times. Each time product is removed from the silo, the silo provides data on the remaining quantity and can independently issue a command to be refilled when a minimum quantity is reached. Once the silo is completely empty, it informs the logistics provider of its pick-up location.
Optimising a circular economy beyond the borders of a company in such a way requires a comprehensive wireless network. For LoRaWAN, this is already the case in the Netherlands, France, and Switzerland. Let’s hope that other European countries will follow these positive examples as soon as possible.