Abstract
The paper presents the concept of a battery-free alarm indicator with a Radio-Frequency Identification (RFID) interface, intended for Internet of Things (IoT) applications, particularly in supply chain networks. The signaling device is powered by energy harvested from the electromagnetic field emitted by an RFID read/write device (RWD). The energy accumulated in the internal capacitor is insufficient for continuous operation outside the interrogation zone (IZ). To overcome this limitation, the negative energy balance can be addressed by employing a physical trigger switch, which activates the power supply circuit upon the occurrence of a guarded physical quantity. This feature is crucial, as it bridges the gap between fully passive RFID tags, which remain inactive outside the interrogation zone, and semi-passive tags, which rely on a built-in battery. The wireless and automatic monitoring capability is especially beneficial for scenarios involving simultaneous reading of multiple transponders.