CN104305985A - Low-power-consumption heart rate monitor and monitoring method thereof - Google Patents

Abstract

The invention discloses a low-power heart rate monitor and a monitoring method thereof, including a three-stage five-stage low-power ECG extraction circuit, a single-chip microcomputer, a display module, a low-power bluetooth chip module and a mobile terminal, based on MSP430F5529 ultra-low Power-consumption single-chip microcomputer, by extracting the I-lead ECG signal, using the differential method to detect the R-wave to realize heart rate calculation and display, and can display waveforms, alarm, and transmit data and ECG images through serial ports or Bluetooth. It can be powered by a 3V~4.5V battery, and uses a combination of active and passive three-op-amp five-level signal extraction circuit and Bluetooth 4.0BLE module, which is low power consumption. The test results show that the ECG signal extracted by this system has little distortion and accurate heart rate calculation, which has a good prospect of popularization and utilization.

Description

A low-power heart rate monitor and its monitoring method

technical field

The present invention relates to the field of low-power heart rate monitors, in particular to a low-power heart rate monitor and a monitoring method thereof.

Background technique

Heart rate monitoring is commonly used in life and clinical practice. It has important uses in exercise intensity detection, physical fitness detection, and disease diagnosis. ECG waveform has greater clinical value. If the heart rate and ECG data can be collected for long-term analysis, it will have greater clinical and scientific value. However, since the ECG signal is a periodic weak signal with a low signal-to-noise ratio, it is easily affected by instruments, human bodies, etc. during the acquisition process, and mixed with strong power frequency interference, so a signal extraction with a certain extraction ability is required circuit.

Existing commercially available heart rate detectors often have a single function and lack some practical additional functions other than heart rate; the data can only be displayed but not transmitted or recorded, and the scope of application is narrow; if more functions are implemented, the power consumption will easily be biased. high. It would therefore be valuable to develop a heart rate monitor that overcomes the above-mentioned shortcomings.

Contents of the invention

The technical problem to be solved by the present invention is to provide a portable, daily-use low-power heart rate monitor, which is more suitable for people's daily health measurement and monitoring needs. The low-power heart rate monitor has a simple structure, and can switch the monitoring function by manipulating the three buttons next to the display, providing users with real-time heart rate times, 30-second average heart rate times, ECG waveforms, ST wave intervals, low heart rate or Too high reminder and many other

utility function.

The technical scheme of the present invention is as follows:

The low-power heart rate monitor includes a three-stage five-stage low-power ECG extraction circuit, a single-chip microcomputer, a display module, a low-power Bluetooth chip module and a mobile terminal. On the copper needle of the power consumption ECG extraction circuit, the output stage of the three-op-amp and five-stage low-power consumption ECG extraction circuit is connected to the single-chip microcomputer through DuPont lines, and the ECG parameters and waveforms processed by the single-chip microcomputer are displayed on the display module on the one hand. , and on the other hand, transmit ECG parameters and waveforms to the mobile terminal through the serial port or Bluetooth module.

The single-chip microcomputer is an MSP430F5529 single-chip microcomputer, the display module is a Nokia5110 display module, and the low-power bluetooth chip module is a CC2540/2541 low-power bluetooth chip module.

The described three-op-amp five-level low-power ECG extraction circuit includes sequentially connected power conversion modules, differential amplifier circuit modules, 1Hz high-pass filter modules, 100Hz low-pass filter modules, 50Hz power frequency notch modules, and amplification and electrical circuits. Lift the module flat.

The power conversion module uses a TPS60400 charge pump voltage inverter, the operational amplifier in the differential amplifier circuit module uses an INA126 differential instrument amplifier, and the operational amplifier used in the 100Hz low-pass filter module is an OPA227 operational amplifier. The operational amplifier used in the module is OPA333 operational amplifier.

The 100Hz low-pass filter module uses a second-order active Butterworth filter, the 1Hz high-pass filter module uses a first-order passive Butterworth filter, and the 50Hz industrial frequency dangerous wave module uses a passive dual T-shaped notch filter.

The software processing of the MSP430F5529 ultra-low-power single-chip microcomputer includes timing and sampling, 50Hz digital filtering, R-wave detection by differential method, calculation of real-time heart rate and average heart rate, self-learning of R-wave detection threshold, system initialization setting and low power consumption. Control, button detection, ST wave interval detection, LCD drive, heart rate interface and heart rate output, waveform interface display and alarm interface display, setting interface display, alarm light switch setting, backlight switch setting, UART serial port sending switch setting , UART serial port data encoding, UART serial port data sent to the low-power Bluetooth chip module.

The mobile APP/HeartRate can receive the data sent by the low-power bluetooth chip module, decode the data, and display the real-time heart rate, average heart rate, ST interval data and ECG waveform.

The data transmission between the Bluetooth low-power chip module and the mobile APP is based on the Bluetooth 4.0 protocol.

The low power consumption heart rate monitoring method of the heart rate monitor is characterized in that it utilizes the I lead line to extract the I lead electrocardiogram signal, and carries out pre-signal processing through the five-level low power consumption electrocardiogram extraction circuit of the three op-amps, and carries out the electrocardiogram signal. Amplify, filter and level up the electrical signal, and then transmit the output signal of the circuit to the single-chip microcomputer. The single-chip microcomputer adopts a sampling frequency of 500 times/s, with key detection, and performs 50Hz digital filtering on the input ECG signal. The single-chip microcomputer uses differential The heart rate is calculated by R wave detection, and the waveform and data are displayed on the display screen. Finally, the ECG parameters and ECG waveform are transmitted to the mobile APP for display through the low-power Bluetooth chip module.

In the low power consumption heart rate monitoring method of the heart rate monitor, key detection is accomplished through the interruption of P1.2 (main key), P1.3 and P1.4 (two auxiliary keys). When the button is pressed, the corresponding IO port is grounded, and a falling edge interrupt is generated. Immediately after that, the interrupt flag is reset, and the button press information is saved in the intermediate variable, and the intermediate variable is reset after the button is processed.

In the low power consumption heart rate monitoring method of the heart rate monitor, the timing is realized by the Timer_B timer carried by the MSP430, and every 1/500s, the MCU in the low power mode LPM0 state is woken up by the timer interrupt to work. Use a timing variable to increase the count from 0 to 29999 to obtain the time within 1 minute.

In the low power consumption heart rate monitoring method of the heart rate monitor, the R wave detection utilizes the characteristic that the rising edge of the R wave in the ECG waveform is much steeper than the rising edge of other waveforms, and uses the second-order difference method to detect the R wave in the ECG waveform .

The low-power heart rate monitoring method of the heart rate monitor uses the UART serial port of the MSP430F5529 (configured with a baud rate of 115200) for communication output, and outputs the real-time heart rate, average heart rate and ECG in a certain string format. data.

The beneficial effect of the present invention is that it can conveniently detect and monitor the normal conditions of ECG parameters in people's daily life, and has the characteristics of simple structure, low power consumption and convenient use.

Description of drawings

Below in conjunction with accompanying drawing, the present invention is further described.

Figure 1 is a schematic structural diagram of a low-power heart rate monitor;

Fig. 2 is the circuit diagram of the pre-differential amplifier circuit of the present invention and the high-pass filter of 1Hz;

Fig. 3 is a circuit diagram of a low-pass filter with a cut-off frequency of 100Hz in the present invention;

Figure 4 is a circuit diagram of the final amplification and level raising circuit of the present invention;

Fig. 5 is a circuit diagram of the 50Hz power frequency notch filter of the present invention;

Figure 6 is a circuit diagram of the negative power conversion module of the present invention;

Figure 7 is a schematic diagram of the heart rate calculation core algorithm of the present invention;

Figure 8 is a structural diagram of the APP interface of the present invention.

In the figure: three operational amplifiers and five-stage low-power ECG extraction circuit 1, MSP430F5529 microcontroller 2, power supply 3, Nokia5110 display module 4, user operation buttons 5, connecting wires between components 6, heart rate data display 7, ECG waveform 8 is displayed.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing 1 to Fig. 8.

Figure 1 shows the basic principle of the system. This system extracts the signal through the combination of active and passive three-stage five-stage signal amplification and filter circuit, and detects the R wave in the ECG waveform through the five-point difference method, and then displays and transmits data, and realizes some additional functions. Function. The power supply can be two 1.5V dry batteries. the

In Fig. 2, a low-power heart rate monitor includes a three-op-amp five-stage low-power ECG extraction circuit in the upper left part of Fig. 2, a power supply battery in the upper right part of Fig. 2, and a single-chip computing and control module in the lower left part of Fig. 2 , and the display screen and control buttons in the lower right part of Figure 2. Figure 2 The upper left part of the three-op-amp five-stage low-power ECG extraction circuit consists of a pre-differential amplifier circuit, a high-pass filter with a cut-off frequency of 1Hz, a low-pass filter with a cut-off frequency of 100Hz, a 50Hz power frequency notch filter and The final amplification and level boosting circuit is composed. The power supply part in the upper right part of Figure 2 is realized by two 1.5V dry batteries, and the negative power supply used by the central electric signal extraction circuit is realized by the TPS60400 charge pump voltage inverter. The single-chip computer calculation and control module in the lower left part of Fig. 2 is realized by MSP430F5529 single-chip computer. MSP430 series single-chip microcomputer is a 16-bit single-chip microcomputer with low power consumption, which can be powered by 3V, and has rich peripheral modules, which is suitable for the realization of this heart rate meter. It can be further divided into two parts: heart rate calculation and system process control. The lower right part of Figure 2 is the output part. Including display output and communication output. The monitor outputs real-time heart rate, average heart rate, ECG waveform, alarm information and some setting information. The display used is Nokia5110 module. The communication output uses the UART serial port that comes with MSP430F5529, and outputs heart rate (immediate, average) and ECG data in a certain string format. If you connect the UART serial port to the USB to UART module, you can send data to the computer. If you connect the UART serial port to the Bluetooth serial port transparent transmission module, you can see the heart rate on Bluetooth devices such as mobile phones. This system uses a module based on TI's CC252541 low-power Bluetooth chip--HM-11 Bluetooth 4.0 BLE low-power Bluetooth serial port transparent transmission module produced by Jinan Huamao Company. And realize the display of instantaneous heart rate and average heart rate on the Android system.

In Fig. 3, Fig. 4 and Fig. 5, the input part of a heart rate monitor with low power consumption includes, one of which is a human body I lead ECG extraction circuit. The second is the input of the user's button operation, which is used to switch various functions. The human body I lead ECG extraction circuit consists of five stages. The first stage is a pre-differential amplifier circuit. Perform pre-amplification, and the processed signal has properties such as low common mode, low noise, and low drift signal. Implemented with INA126 differential amplifier. The second stage is a high-pass filter with a cutoff frequency of 1Hz. Dealing with baseline drift. It is realized by RC passive filtering. The third stage is a low-pass filter with a cutoff frequency of 100Hz. Deal with high-frequency interference. It is implemented by a second-order Butterworth active filter, and the op amp is a precision op amp OPA227. The fourth stage is a 50Hz power frequency notch filter. Minimize the power frequency interference as much as possible, so that the identifiable ECG waveform can be displayed on the oscilloscope. It is realized by double T-type passive filter. The fifth stage is the final amplification and level boosting circuit. An OPA333 single-supply op amp is used to form the same-phase proportional adder, and the ECG signal is finally amplified to an amplitude of about 1V, and superimposed with the power supply voltage division, and raised to the range of 1~2V. The 3.3V single-supply op amp also protects the ADC. Then send it to the ADC module. In order to ensure the signal quality, the method of grounding the right leg is adopted, that is, connecting RL to the GND of the system. The system design input impedance is 40MΩ, and the total magnification is about 500 times at 25Hz as measured by step-by-step simulation.

Figure 6 shows the heart rate calculation process of a low-power heart rate monitor.

The heart rate calculation principle is as follows.

ECG signals are input from the ADC at a sampling frequency of 500 times/s.

Afterwards, 50Hz smoothing digital filtering is performed. The filtering method is a smoothing filtering method, that is, the average value of the current and the previous 9 ADC sampling results is used as the current ECG data. Let x represent the ADC sampling result, and y represent the ECG data obtained after processing, then y(n)=[x(n)+x(n-1)+x(n-2)+x(n-3)+ x(n-4)+x(n-5)+x(n-6)+x(n-7)+x(n-8)+x(n-9)]/10.

Then perform five-point difference processing. If the differential result is represented by z, then z(n)=2y(n)+y(n-1)-y(n-3)-2y(n-4).

Compare the five-point differential value with the threshold m, and every time m is exceeded, it will be recorded as an R wave, which is used as the basis for judging the ECG R wave (but if the interval between the two detected R waves is too short (less than 0.16s, that is, If the heart rate is greater than 375 beats/min), the second R wave is considered to be a false wave and will not be counted) Then the real-time heart rate is calculated according to the interval time of the 3 R-waves, the formula is real-time heart rate=90000/(time difference of 3 R-waves ); Calculate the average heart rate based on the number of R waves within a certain period of time (15s, 30s, 60s).

The threshold is obtained through a self-learning algorithm, and the calculation formula is threshold m=(maximum value of ECG data within 2 seconds-minimum value of ECG data within 2 seconds)*0.5.

Figure 7 shows the flow control of the system. System flow control is realized by programming the MSP430F5529 microcontroller. When the system is idle, the microcontroller enters the LPM0 low-power mode to save power. Control the function mode of the system through 1 main button and 2 auxiliary buttons, you can choose the display mode of heart rate and average heart rate, ECG waveform mode, alarm mode, and can set the switch of backlight, alarm light and communication function. In either mode, the collection of ECG signals and the calculation of heart rate are performed in real time.

Figure 8 shows the heart rate display on the Android system, including functions such as instantaneous heart rate and 15-second average heart rate.

Claims (9)

1. a low-power consumption heart rate monitor, it is characterized in that comprising three amplifier Pyatyi low-power consumption electrocardios extracts circuit, single-chip microcomputer, display module, low-power consumption Bluetooth chip module and mobile terminal, the I conducting wire connecting human body is enclosed within three amplifier Pyatyi low-power consumption electrocardios and extracts on the copper pin of circuit, the output stage that three amplifier Pyatyi low-power consumption electrocardios extract circuit is connected by Du Pont's line with single-chip microcomputer, EGC parameter after single-chip microcomputer process and waveform, be presented on display module on the one hand, pass through serial ports or bluetooth module transmission EGC parameter and waveform on the other hand to mobile terminal.

2. a kind of low-power consumption heart rate monitor according to claim 1, it is characterized in that described single-chip microcomputer is MSP430F5529 single-chip microcomputer, display module is Nokia5110 display module, and low-power consumption Bluetooth chip module is CC2540/2541 low-power consumption Bluetooth chip module.

3. a kind of low-power consumption heart rate monitor according to claim 1, is characterized in that three described amplifier Pyatyi low-power consumption electrocardios extract circuit and comprise power transfer module connected in turn, differential amplifier circuit module, 1Hz high-pass filtering module, 100Hz low-pass filtering module, 50Hz notch filter module and amplify and level lifting module.

4. a kind of low-power consumption heart rate monitor according to claim 3, it is characterized in that described power transfer module adopts TPS60400 charge pump voltage reversal device, what the amplifier in differential amplifier circuit module adopted is INA126 difference instrument amplifier, the operational amplifier that 100Hz low-pass filtering module adopts is OPA227 operational amplifier, and amplifying the operational amplifier adopted with level lifting module is OPA333 operational amplifier.

5. a kind of low-power consumption heart rate monitor according to claim 3, what it is characterized in that described 100Hz low-pass filtering module employing is second order active Butterworth filter, what 1Hz high-pass filtering module adopted is the passive Butterworth filter of single order, and what 50Hz power frequency danger mode block adopted is passive double-T shaped notch filter.

6. a kind of low-power consumption heart rate monitor according to claim 1, it is characterized in that the software processes of described MSP430F5529 super low power consuming single chip processor comprises timing and sampling, 50Hz digital filtering, calculus of finite differences R ripple detects, the calculating of instant heart rate and average heart rate, the self study of R ripple detection threshold, system initialization setting and low power consumption control, button detects, ST wave spacing detects, liquid crystal drive, heart rate interface and heart rate export, rippled interface display and alert interface display, the display at setting interface, alarm lamp switch sets, backlight switch sets, UART serial ports transmit button sets, UART serial data is encoded, UART serial data is sent to low-power consumption Bluetooth chip module.

7. a kind of low-power consumption heart rate monitor according to claim 1, is characterized in that data that described mobile terminal APP/HeartRate can receive low-power consumption Bluetooth chip module and send, carries out data decoding, shows instant heart rate, average heart rate, ST interval data and ecg wave form.

8. a kind of low-power consumption heart rate monitor according to claim 1, it is characterized in that described low-power consumption Bluetooth chip module and mobile terminal APP carry out that data transmit is based on bluetooth 4.0 agreement.

9. the low-power consumption heart rate monitoring method of a Cardio kickboxing as claimed in claim 1, it is characterized in that utilizing I conducting wire to extract I to lead electrocardiosignal, extract circuit through three amplifier Pyatyi low-power consumption electrocardios and carry out advance signal process, carry out the amplification of electrocardiosignal, filtering and level lifting, then circuit output signal is imported into single-chip microcomputer, single-chip microcomputer adopts the sample frequency of 500 times/s, detect with button, and 50Hz digital filtering is carried out to the electrocardiosignal of input, single-chip microcomputer utilizes the detection of calculus of finite differences R ripple to carry out heart rate calculating, the display of waveform and data is carried out on display screen, finally by low-power consumption Bluetooth chip module, EGC parameter and ecg wave form are transferred to mobile terminal APP show.