Abstract
One of the biggest impacts of the vision ‘Internet of Things’ is the massive number of connected devices, where billions of nodes will exchange data, information and commands. While wireless systems offer advantages such as increased flexibility, they also introduce one major challenge: how to power each individual node. In many cases, there is no way around the use of batteries. To minimize the environmental impact, increasing the battery’s longevity is the most important factor. This paper introduces a wireless battery-assisted node that has a drastically reduced energy consumption in the standby mode. The state (on/off) will be changed by harvesting a radiofrequency signal. A latching switch connects or disconnects the load—for example, a microcontroller—and the battery. The switch is connected to a charge pump which converts an AC (alternating current) signal into a usable DC (direct current) control signal. An antenna is mounted to the charge pump via a matching network. An electromagnetic wave is emitted by a remote control switch that switches the system on and off. The used frequency is MHz and therefore in the UHF RFID (ultra high frequency radio frequency identification) band. The measurement results show that the wireless node consumes less than in the standby mode. The remote controlling is possible from a distance of more than . The presented system can be integrated in further work on a UHF RFID tag. Thus, the existing protocol standard can be used to identify the object to be switched. By custom commands, the switching request can be transmitted from the remote control (UHF RFID reader) to the switching node.
Highlights
The Internet of Things (IoT) describes a network of billions of devices
This paper shows a way to switch battery-assisted wireless nodes on and off in a network by an external remote control using UHF RFID
In order to keep the state, a latching switch topology has been proposed which can be controlled by a single MOSFET transistor
Summary
The Internet of Things (IoT) describes a network of billions of devices. Each single node can be a small sensor, a microcontroller (μC) as well as a whole laptop or smartphone. Battery-less systems use energy harvesting to power the passive node and transmit data. The node is woken up even if it is not necessary, which leads to additional energy consumption. This method is used in LTE-M, which is specified for IoT [4]. The presented 5 V battery-assisted wireless node has an standby consumption of ∼ 16 nW and can be woken up by a remote control. The used switch needs to operate in latching mode to keep its on/off state Without this feature, the node would only be powered as long as an RC sends a continuous wave (CW) [19]. The switching request can be implemented by a custom commands
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