A Smart Parking Sensor with Multi-purpose Antenna for Car Detection and Sensor Charging

Traffic and parking management is an important topic in modern cities. In particular open parking areas are challenging in terms of monitoring. In this paper a novel parking sensor is demonstrated, which allows detection of cars and charging of the sensor unit via one single inductor. As a proof-of-concept hardware, a small scale model of the system is implemented. For wireless power transfer the QI-standard is employed. In order to a achieve reasonable battery lifetimes the design aims to low current consumption. Power management is performed by a micro controller, which allows switching on and off external components. Furthermore detection is performed via a Colpitts oscillator circuit. The oscillation frequency of the detector lies typically around 650 kHz, whereas in the presence of a model car it increases up to 800 kHz, which is detected by a microcontroller. In the range from 14°C to 30 °C a temperature dependence of -0.4 kHz/°C is found, which is acceptable for the present system. Anyway, a temperature sensor allows a correction of thresholds for car detection. Finally, the up scaling of the model to real world size and potential problems are discussed.