Health monitoring systems become a hot topic and important research field today. Research on health monitoring were developed for many applications such as military, homecare unit, hospital, sports training and activity emergency monitoring system. In this paper, we developed the wearable and real-time monitoring system of some critical vital signs for elderly people, because Thai people who ages over 60 years old encounter accidental incidents over 60 percent. [1] That system may help doctor or people in family monitor the emergency alarm from patient or elderly people. The vital signs of health status that are the important parameter in health monitoring system consist of blood pressure, heart rate, oxygen saturation, body temperature and respiratory rate.[2] In this work, we consider two parameters of the vital signs which are heart rate and oxygen saturation in blood. That vital sign can measure by using device namely; pulse oximeter. The pulse oximetry data are important for doctor to monitor patient’s health condition.

Microcontroller Based Wireless Temperature And Heart Beat Read Out suitable for operation in a small office/home environment. This system is easy to operate, with Visual LCD. Many individuals and organizations may, for various reasons, wish to use electronic surveillance techniques at some time or another. The idea is to use off-the-shelf RF Tx/Rx modules. The weather keeps us continually occupied. Some people have even made it their profession. At home too, we like to measure all kinds of things related to our climate. That is why weather stations are available in all types and sizes. If we want to know the temperature inside and outside then purpose-built indoor/outdoor thermometers are available. In the past the outside sensor of these weather stations was connected with a wire, it is now fairly standard to use RF transmission for this data.

This Wireless transmitters units usually make use of the 315-MHz band. These modules, once a rare commodity, are now widely and cheaply available. In this particular discussion, we shall be using ASK (Amplitude Shift Keying) based TX/RX pair operating at 315 MHz. The transmitter module accepts serial data at a maximum of 2400bps. They are directly interfaced to a microcontroller. At the RX end, the receiver microcontroller receives the signal via the RF receiver module, decodes the serial data and reproduces the original data in the temperature and Heat Beat format. 

Wireless technology was developed in many applications that becoming a part of human activities such as agriculture, military, medical care, smart home system etc. Distinctly, wireless sensor networks (WSN) play a crucial role in such a monitoring system application, for the reason that WSN can offer some advantages over other types of wireless systems, especially its scalability, power management and flexibility of architecture. As a matter of fact, there are two popular standards in the wireless personal area network (WPAN), namely, Bluetooth and ZigBee. This work was focused on the capability of wireless sensor networks as an efficient tool to monitor health in term of pulse oximetry data for demonstration. This situation makes it difficult to develop and challenge because many applications in WSNs developed for fixing the position of member in wireless personal area network (WPAN). We adopted the ZigBee for using as a real-time health monitoring system on a patient.

Pulse Oximeter Transmitter Module

A typical oximetry sensor has a pair of light emitting diode (LEDs). The two types of light emitting diode consist of infrared and red light. The infrared has a wavelength of 905 nm and red light has a wavelength of 660 nm. A pair of light emitting diodes (LEDs) facing with a photo detector module on patient’s finger. The photo detector module used is PDI-E832, which combines the two types of light detection in one module for minimizing the size of sensor probe. The entire optical device was assembled on Velcro strip with metal wire frame for easy to be worn by the patient. Figure 1 depicts block diagram of sensor module unit. The system consists of a microcontroller unit, two series of Li-Ion cells, power supply circuit, photo-detector module, ZigBee module, digital to analog converter IC, operating amplifier IC, driver circuit for red LED and infrared LED, couple of lightemitting diode (LEDs). Figure 2 depicts the system developed for using by patient in daily life. The entire system should be a low weight, low power consumed and comfortable to wear device. In this work, we use microcontroller unit for controlling the processing in the sensor module, which features nano-watts technologies microcontroller. The microcontroller starts the process by sending digital data to digital to analog converter and the output was amplified by operating amplifier IC. After that, the signal from operating amplifier IC are driven the couple of LEDs in the difference time. Microcontroller unit can get the signal from photo detector through finger tissue and calculate to find the SpO2 level; also the heart rate can get directly from pulse of infrared LED.

The data such as heart rate, SpO2, battery indicator and wireless signal strength are stored in microcontroller and be ready for sending to base nodes. ZigBee module provides AT-command for controlling from microcontroller unit such as request to send (RTS) the data or get the signal strength indicator. The power management of sensor node system is also controlled by microcontroller unit. The microcontroller unit reads the value of the battery voltage indicator to select proper period of time to send the data and time to sleep. In each node, it has various times to send the data that depend on total of power consumption in each node. Such as, if the battery has remaining energy more than 80%, sensor node is allowed to perform full function by transmitting data every 5 seconds. If the battery has remaining energy lower than 30%, system will extend the sleep period by transmitting data every 10 seconds. The data from each node in every second are kept and stored for sending to base node but the time to send will depend on power consumption in each sensor and that time controlled the switching of time for cyclic sleep mode in ZigBee module. In this work, two series cells of Li-Ion with a capacity of 1000 m-AH was employed because we need the light weight and small assembled size of sensor.