Based on JN5139 wireless sensor networking pulse monitoring system design of body temperature (1)

Summary: ask a support body temperature and pulse monitoring of ZigBee wireless sensor network system.

Sensor terminals, wireless routers and base stations 3 class based on the micro-controller node JN5139 device through the network regularly collect field measurements of body temperature and pulse parameters, using computer for centralized storage and management. The system has high accuracy, connectivity, scalability, and low power consumption.

Introduction

Temperature and pulse is reflected the important human health, patient physiological indicators of these physiological indicators continuous monitoring, diagnosis and treatment for diseases of the right to provide an important basis.

As sensor technology, embedded computing technology and wireless communication technologies for development, based on wireless sensor networks vital signs monitoring systems are more and more attention. Among them, based on the normal RF chip and a custom transport protocol of the system has a simple and low-cost advantages, disadvantages are low, the versatility of reliability is poor; a system based on Bluetooth protocol data rates are relatively high, but the distance is short, the power consumption and high capacity, network as weak; built on ZigBee IEEE 802.15.4 low-speed communication standards for wireless personal area network (Low-Rate Wireless Personal Net-work, LR-WPAN) protocol specification, the complexity of the system has a low, low power consumption, high reliability, network capacity, etc., become the focus of research in the field of application.

This article proposes a support body temperature and pulse monitoring of ZigBee wireless sensor network systems, network regularly collect field measurements of body temperature and pulse parameters, and use the computer for centralized storage and management, improving the monitoring of the efficiency and quality.

The system has high reliability, scalability, and low power consumption, low cost advantages.

1 monitoring system architecture

Monitoring system including sensor terminals, wireless routers and base stations have three types of nodes to self-organizing manner constitute a ZigBee mesh wireless sensor network, as shown in Figure l.

Temperature sensor Terminal is responsible for detecting and pulse, test results, through their parent node router sends to the base station. Base station with upper monitoring software to receive the data storage and display, and according to user needs to display the current status of the network structure and devices, set the sampling period and alarm threshold, the output changes reflecting the condition of records and historical curve.

2 node hardware structure

2.1 JN5139 wireless micro-controller

ZigBee node device hardware implementations are divided into two major categories: one category is the RF transceivers and separation of micro-controllers, each with 1 chip, user device class (Coordin-ator, Router, Device End) and feature selection for optimal mix; the two integrated in a chip, you can simplify device hardware design, improving the system of hardware reliability.

JN5139 is Jennic company launched the second generation single-chip IEEE 802.15.4/ZigBee wireless micro-controllers, embedded 32-bit RISC CPU, 2.4GHz IEEE 802.15.4 RF transceiver, 192 KB ROM, 96 KBRAM, as well as a wealth of parallel, serial, timer, A/D and D/A, interface resource.

In order to improve products, electromagnetic compatibility JN5139 chip, Crystal 16 MHz, 128 Flash KB serial memory, antenna, ceramics components consolidation become universal module to its core, combined with appropriate peripherals, protocol stacks and application code, you can implement different types of ZigBee node device.

2.2 sensor Terminal

As shown in Figure 2, the sensor terminal by JN5139 minimum system, temperature detection circuit, pulse circuit composition detection, using 3.6 battery V NiMH power supply.

Minimum system including JN5139 module, reset components R1 and C1, status indicator D1 and program download interface j1. Power-on reset, JN5139 internal ROM of Bootloader automatically detect MISO pin level. If it is high, the direct serial Flash outside of the films in the program code is loaded into the RAM chip; if it is running in a low, then into programming, through the serial port 0 download PC for the latest code, and writes Serial Flash.

Temperature measurement circuit consists of high-precision resistance NTC thermistor RT and precision resistance R3 ~ R5.

JN5139 by making DI01 output low level to control the temperature measuring circuit, using three 12-bit A/D conversion channel separately measured 3 points of potential, thermistor seeking out of resistance, and then use thermistor R-T relational tables and linearization formula to get the appropriate temperature.

Pulse detection circuit including photoelectric sensor and signal conditioning circuits, as shown in Figure 3.

Photoelectric sensor consists of a red light launch tube D1 and triode Q1 photosensitive, both relative to shading within a set. Measuring pulse, part of the light emitted by finger, exposure to phototransistor of photic, transmitted light intensity with pulse fluctuation render very small changes, the phototransistor optically a power conversion, output DC and weak Exchange phase voltage signal superposition of mixed. The signal across direct, low-pass filtering and amplifying processing, become a peak close to Vcc/2 analog pulse signal carried by JN5139 A/D conversion, digital filtering and cycle the judgment, the finalGet to min-pulse rate values. In order to resolve individual differences, and so causes pulse output signal saturation or too small, the emission tubes operating current by JN5139 through d/a converter automatically adjust.