Sensor Design for Inductive Proximity and Moving Direction Sensing of Metal Targets

We present the design of a new inductive proximity sensor to detect metal targets and their direction of movement. The proposed sensor design includes a base board with the necessary microcontroller based circuitry for driving and reading the sensing LC tanks and several different solutions for the printed sensor coil. Different coil configurations are fabricated on separate printed circuit boards designed to plug-and-play into the base board. They are intended for different specific applications including for sensing metal targets approaching perpendicularly on the coil plane and for sensing and identifying the lateral direction of movement (i.e., left-to-right or right-to-left). The coil designs are studied via simulations using the freely available Numerical Electromagnetics Code (NEC). A complete hardware prototype is developed and demonstrated to detect different metal targets, including copper, brass, aluminum, and stainless steel. It is also shown that measurements obtained from hardware experiments are in good agreement with the simulations.