Circuit Design of a Smart Bluetooth Apparel System for Physiological Monitoring

7050 OSC seed vibration

Test - lowercase jpg

With the development of the economy and the improvement of living standards, people's health requirements are getting higher and higher, and there is an urgent need for a convenient and quick way to know their own vital signs. However, conventional medical testing equipment has the disadvantages of inconvenient operation, poor portability, and difficulty in further analysis of data. With the rapid development of sensor technology, material technology and wireless communication technology, the combination of medical monitoring equipment and clothing can better meet the needs of people. In this paper, a wearable multi-parameter monitoring intelligent clothing system is proposed, which integrates sensors, fabric cables and flexible circuit boards into clothing, realizing dynamic and collaborative monitoring of multiple physiological parameters in daily life and working environment. Signal detection, signal feature extraction, and use Bluetooth technology to complete data backup for further analysis, or use Bluetooth-enabled communication equipment to achieve remote medical services and other functions.

Monitoring sensor circuit design

The sensor is responsible for measuring the collection of vital signs such as heart rate and body temperature. Considering the wearable features of the system, in terms of sensor selection, products with integrated, high sensitivity and high precision should be selected as much as possible, which can reduce the area of ​​the system circuit, facilitate wear, and improve the stability and reliability of the system. Sex. The blood pressure collection module uses the MPXV5050GP piezoelectric sensor produced by Freescal, and is placed inside the elbow joint of the middle of the sleeve. This can directly convert the pressure of the arterial blood to the blood vessel wall into an output electrical signal. The specific circuit is shown in the figure. The sensor uses an ion implantation process, and integrates a signal processing unit circuit such as an amplifier and a filter. The external device requires only a few components to operate. The amplified and shaped electrical signal is output at the output, so that the output of the sensor is directly connected to the ADμC7024's internal 12-bit ADC for analog-to-digital conversion. The blood pressure value is obtained by software processing.

PVDF piezoelectric film has the characteristics of light weight, soft texture, good durability and large dynamic range of piezoelectric response. Multi-layer contact piezoelectric film sensor is used to measure heart rate, which can reduce interference signals. The heart rate acquisition module uses the HK-2000H integrated digital pulse sensor, which is placed on the left chest of the garment to measure heart rate. HK-2000H integrates PVDF piezoelectric film, high-sensitivity temperature compensation component, temperature sensing component, program-controlled amplifier circuit, signal conditioning circuit, filter circuit and A/D conversion circuit. Integration avoids the disadvantage of using a discrete component design circuit to occupy a large area. The schematic is shown in Figure 3. The HK-2000H integrated digital pulse sensor uses a USB port output for easy software processing of its output.

The body temperature acquisition module uses Maxim's analog temperature sensor MAX6612 to detect body surface temperature. The MAX6612 is available in a 5 PIN SC70 package with a maximum operating current of only 35μA. It features low power consumption, high accuracy, and small size. It is optimized for the ADC and is suitable for this system. The specific body temperature acquisition circuit is shown in the figure.

The relationship between the output amplitude of the MAX6612 and the measured temperature satisfies the expression.

The measured output electrical signal is analog-to-digital converted by a 12-bit successive approximation ADC on the ADμC7024 processor. The conversion result will be stored in the ADCDAT0 register. The ADC bit status register can be used to see if the ADC conversion is complete. At the end of the conversion, the lowest bit is set. The measured body surface temperature is obtained according to the above algorithm by reading the value in the register ADCDAT0 and then using software.

Bluetooth module circuit design

The system uses a Bluetooth module to implement data exchange with an external device embedded with Bluetooth. In order to reduce system size, reduce system quality and reduce power consumption, the Bluetooth module adopts Class-2 design scheme, USB output, transmission distance of 10 m, and supports Bluetooth 2.0 version protocol to meet system requirements. The Bluetooth chip uses CSR's BC417413. The chip integrates 8 MB of flash memory. It mainly stores the software of the baseband, link management layer and host control interface, and also includes some APIs for configuring the chip. The front-end RF bandpass filter uses MDR771F-CSR-T. Barron uses TDK's HHM-1517 to complete the conversion between the system's differential RF signal and the antenna input and output signals. The schematic diagram of the specific design scheme is shown in Figure 5.

This system supports the expansion of system functions. For the actual needs of patients with diabetes and hypertension, modules such as blood glucose and blood oxygen can be installed to perform non-invasive continuous monitoring of blood sugar and blood oxygen. Allows the wearer to take measurements at any time, making it easy to operate. A smart clothing system for life monitoring was proposed and designed, and the appropriate working mode can be selected according to the needs of users. At the same time, the system uses the Bluetooth technology to network the external devices such as the human body, the smart phone and the computer, and can back up the collected vital signs data, and facilitate the development of the telemedicine service.