Polydimethylsiloxane‐based capacitive motion sensor and its read‐out circuit

A capacitive motion sensor that can detect human walking and motions up to a certain distance was designed using polydimethylsiloxane (PDMS) as the primary sensor material. A read‐out circuit was designed to detect capacitive coupling with the sensor material caused by the motion in the surrounding. The read‐out circuit consists of sensing, filtering, and amplifying stages. A high‐pass filter was used to avoid DC components, and to eliminate adverse impacts of 50Hz noise in the sensing signal, a sixth‐order low‐pass filter consisting of active Sallen–Key and passive RC filters was utilized. The signals obtained from the complete read‐out circuit revealed that the sensor system could accurately detect human movements up to 2 m away. Also, different signal patterns were obtained from the output of the sensor system for various human motions.