The Design Of Wireless Heart Sounds Sensor Node Based On ZigBee

The study and analysis of heart sounds signal is important as it help to evaluate the reserve capacity of our hearts. At present, most of the hospitals use heart sounds detector that connects the sensor with patient to transmit signals. It is so troublesome as there are so many equipments and wires, and it may make mistakes in the result as patients feel nervous. In this paper, I put forward a design proposal of a wireless heart sounds sensor node based on ZigBee by analysing wireless multimedia sensor network and networking protocol.The hardware of wireless heart sounds sensor node consists of data acquisition unit, data processing unit, data transmission unit and power supply unit. The data acquisition unit includes signal acquisition circuit, analog filter amplifier circuit, gain control circuit and level conditioning circuit. The processed analog signal would fluctuate in 0~3V,then then signal will be transmitted to A/D conversion circuit. It is simple and efficient that data processing and transmission units of the node are designed based on ZigBee chip system (SOC) CC2430 chip and its periphery circuits. Power supply unit provides±5V and + 3.3 voltage. The software design consists of A/D sampling circuit driver programming design, data storage driver programming design, wireless transfer module application layer protocol design and user control centre software design.By building simple star network, users can send collecting order to collecting node by user interface. And then the terminal node sends signals to base station. And then the base station communicates with PC and shows the heart signal by user interface. And we can extract the parameters in the heart signal to analyze pathology. This scheme realizes the design of heart sounds wireless sensor node and make the function and performance testing in the network. In the function testing, according to contrast of the heart sound signals collected from the terminal node and base node,it is known that basically there is no deformation in the heart sound wave through the ZigBee network transmission, but the signal is blended with many noises, making the signal wave appearing much burr. Partial the second heart sound S2 may have been covered by noises, and the data packets losing in the transmission process may also make S2 not normally collected. But it does not affect effective recognition of the signal. We select the clear wave segments which can be extracted parameters to analyze pathology after denoised and algorithm simulated. In the performance testing, a terminal node continuous sends fixed size (256 bytes) packets to base station, and no packet loses in 10m indoor, but few packets lose out of 20m outdoor due to the increase of interference, and along with the increasing distances, the signal strength is more and more weak. At the respect of Power test, the power of working mode and sleeping mode respectively are 736mW and 198uW that are expected to reach the experimental effect.