A Wearable Breath Detection Device Based on Capacitive Coupling

Human respiratory status information is not only of great significance in medical application, but also helps people monitor their own health status. The existing breath detection methods are mostly contact or invasive methods, which are easy to bring discomfort to users. In real life, using wireless and non-invasive equipment to monitor the respiratory process in real time has become more and more important, which can not only reduce the pain of patients, but also provide sufficient information for the early detection and diagnosis of diseases. The parallel plate is coupled with the human body to form a coupling capacitance. The small displacement of the electrode in the process of breathing movement will lead to the change of capacitance value. The change of capacitance value is directly related to the distance between the electrode and the skin. There is no direct contact between the sensor and the human body, so as to realize the non-contact detection of respiratory information. In the wearable respiratory detection device designed in this study, the capacitance signal coupled by the parallel plate and the abdomen is collected by the fdc2214 capacitance sensor chip and transmitted to the mobile phone app through the microcontroller through the wireless LAN, so as to realize the real-time detection of respiratory signal. Healthy volunteers were recruited to participate in the comparative monitoring experiment using the existing mode and capacitive coupling mode. The experimental results show that the proposed method can stably measure the breathing of the experimental object, correctly reflect the breathing frequency of the experimental object, and the measurement error is within 3%. The research shows that the output signal of capacitive coupling monitoring respiratory signal has good reliability and feasibility. The experimental self powered sensing device can be used for real-time, continuous and noninvasive monitoring of subtle muscle movement and human respiratory state.