A three-electrode capacitive based sensing system to determine the direction of motion of humans

This paper presents a novel capacitive sensor-based proximity detection system that can sense and determine a human being’s presence and the direction of motion. The proposed system consists of a coplanar-based three-electrode capacitive sensor and a sensor interface circuit that can accurately determine the direction of motion of humans and remain insensitive to other objects. The capacitive sensor structure is easily mountable on the side jamb of a door. Due to the shielding effect, the sensor capacitance value decreases, and a unique pattern in the sensor output is observed, based on the direction of motion of the human beings passing through the doorway. A simulation study conducted in ANSYS Multiphysics-based environment with copper electrodes of length 30 cm and width 1.2 cm will give a detection range of 50 cm. The same is experimentally verified through a prototype developed in the laboratory and the overall power consumption of the proposed system is around 27 mW. Rigorous tests are conducted to evaluate the performance of the system, and the experimental results indicate the versatility and the potential of the system.