A wearable baby sleep monitoring device

Abstract

The utility model relates to a wearable baby sleep monitoring device, include: main flexible pressure sensor, the pressure signal that the abdominal movement caused by sleep breath produces is perceived as first resistance signal, main linear conversion circuit, with main flexible pressure sensor connection constitutes main differential bridge structure, difference amplification circuit, connects main linear conversion circuit, two order Butterworth low pass filter circuit, connects difference amplification circuit, double T type active trap wave circuit, connects two order Butterworth low pass filter circuit, microcontroller, connects double T type active trap wave circuit. The utility model integrates flexible pressure sensor and hardware circuit together, and the volume is small, wearable, can realize multi -environment detection, has the portability, simultaneously, simple structure, low in cost, easy operation, and, fix flexible pressure sensor in abdominal collection breath signal, and the sensitivity is higher, and the environment interference is small.

Description

Technical Field

[0001] This utility model relates to the field of health monitoring, specifically to a wearable infant sleep monitoring device. Background Technology

[0002] Infants (<1 year old) secrete approximately 75% of their daily growth hormone during deep sleep, and breathing is one of the basic vital signs. Sleep apnea monitoring in infants can promptly detect respiratory abnormalities, such as rapid breathing, slow breathing, and apnea, reducing the risk of death from illness or accidents.

[0003] Current research on respiratory signal monitoring categorizes it into direct and indirect methods. Direct monitoring often uses thermal resistance sensors to measure the velocity or flow rate of respiratory airflow; indirect monitoring typically uses strain sensors to measure stress changes caused by the stretching of the skin in the chest or abdomen during respiration to reflect respiratory status. There is also sleep detection using pyroelectric infrared sensors to receive signals emitted by the human body.

[0004] In clinical medicine, multimodal signal monitoring devices are commonly used. By collecting electroencephalogram (EEG), electrooculogram (EOG), and electromyogram (EMG) signals, continuous monitoring of indicators such as respiration, arterial blood oxygen saturation, EEG, and ECG can be performed to accurately assess the severity of sleep apnea symptoms.

[0005] Besides these, the most common instruments on the market for monitoring infant respiration are maternal and infant monitors, which can monitor an infant's vital signs such as body temperature, heart rate, and respiratory rate in real time. These instruments have the following problems:

[0006] 1. If sensors such as pyroelectric infrared sensors are used for identification, they are easily affected by fluctuations in ambient temperature and it is difficult to distinguish between breathing movements and limb movements.

[0007] 2. Multimode signal monitoring devices have complex structures and high costs, making them difficult to widely use in homes.

[0008] 3. The instruments have poor individual adaptability, are large in size, and have complicated operation procedures. Utility Model Content

[0009] This invention provides a wearable infant sleep monitoring device to solve at least one of the above-mentioned technical problems.

[0010] The technical solution of this utility model to solve the above-mentioned technical problems is as follows: A wearable infant sleep monitoring device, comprising:

[0011] The main flexible pressure sensor is used to sense the pressure signal generated by abdominal movement caused by sleep breathing as a first resistance signal;

[0012] The main linear conversion circuit, connected to the main flexible pressure sensor, forms a main differential bridge structure, used to perform linear conversion on the first resistance signal to obtain a first differential voltage signal containing common-mode interference;

[0013] A differential amplifier circuit, connected to the main linear conversion circuit, is used to suppress the common-mode interference and enhance the first differential-mode voltage signal to obtain an amplified signal;

[0014] A second-order Butterworth low-pass filter circuit is connected to the differential amplifier circuit to filter out high-frequency interference in the amplified signal and obtain a low-pass filtered signal.

[0015] A dual-T active notch filter circuit is connected to the second-order Butterworth low-pass filter circuit to filter out power frequency interference in the low-pass filter signal and obtain an electrical signal for characterizing sleep breathing.

[0016] A microcontroller, connected to the dual-T active notch filter circuit, is used to sample the electrical signal to achieve sleep breathing monitoring.

[0017] Based on the above technical solution, the present invention can be further improved as follows.

[0018] Furthermore, the main flexible pressure sensor is provided in one or two configurations.

[0019] When the main flexible pressure sensor is provided, the main linear conversion circuit includes three preset resistors, a main bridge power supply terminal and a main ground terminal. The main flexible pressure sensor and the three preset resistors form a main differential bridge structure. The main bridge power supply terminal and the main ground terminal are connected to a pair of diagonals of the bridge arms in the main differential bridge structure. The other pair of diagonals of the bridge arms in the main differential bridge structure are connected to the main linear conversion circuit.

[0020] When there are two main flexible pressure sensors, the main linear conversion circuit includes two preset resistors, a main bridge power supply terminal and a main ground terminal. The two main flexible pressure sensors and the two preset resistors are arranged in a cross manner to form a main differential bridge structure. The main bridge power supply terminal and the main ground terminal are connected to a set of diagonal points of the bridge arm in the main differential bridge structure. The other set of diagonal points of the bridge arm in the main differential bridge structure is connected to the main linear conversion circuit.

[0021] The voltage at the main bridge power supply terminal is 3.3V, and the main grounding terminal is grounded.

[0022] Furthermore, the differential amplifier circuit includes:

[0023] The first operational amplifier, model INA333, has its VIN+ and VIN- pins connected to the main linear conversion circuit, its V+ pin connected to a 5V power supply, its V- and REF pins grounded, and its VOUT pin connected to the second-order Butterworth low-pass filter circuit.

[0024] The first resistor is connected between the two RG pins of the first operational amplifier.

[0025] Furthermore, the second-order Butterworth low-pass filter circuit includes:

[0026] The second resistor is connected at one end to the differential amplifier circuit.

[0027] The third resistor is connected at one end to the other end of the second resistor;

[0028] The second operational amplifier has its non-inverting input connected to the other end of the third resistor, its output connected to the double-T active notch filter circuit, its positive power supply connected to a 5V power supply, and its negative power supply grounded.

[0029] The fourth resistor has one end connected to the inverting input of the second operational amplifier and the other end grounded.

[0030] The fifth resistor is connected between the inverting input and output terminals of the second operational amplifier.

[0031] The first capacitor has one end connected to the non-inverting input terminal of the second operational amplifier, and the other end grounded.

[0032] The fifth capacitor has one end connected between the second resistor and the third resistor, and the other end connected to the output terminal of the second operational amplifier.

[0033] Furthermore, the dual-T active notch filter circuit includes:

[0034] The sixth resistor is connected at one end to the second-order Butterworth low-pass filter circuit.

[0035] The seventh resistor is connected at one end to the other end of the sixth resistor;

[0036] The second capacitor is connected at one end to one end of the sixth resistor;

[0037] The third capacitor has one end connected to the other end of the second capacitor and the other end connected to the other end of the seventh resistor.

[0038] The eighth resistor has one end connected between the second capacitor and the third capacitor, and the other end grounded.

[0039] The fourth capacitor has one end connected between the sixth and seventh resistors, and the other end grounded.

[0040] The third operational amplifier has its non-inverting input connected to the other end of the seventh resistor, its positive power supply connected to a 5V power supply, its negative power supply grounded, its inverting input connected to the output, and its output connected to the microcontroller.

[0041] Furthermore, it also includes:

[0042] A flexible pressure sensor is used to detect the pressure signal generated by lying face down as a second resistance signal;

[0043] An auxiliary linear conversion circuit, connected to the auxiliary flexible pressure sensor to form an auxiliary differential bridge structure, is used to linearly convert the second resistance signal to obtain a second differential voltage signal used to characterize sleeping posture.

[0044] The sleeping posture detection circuit, connected to the auxiliary linear conversion circuit and the microcontroller, is used to compare the second differential voltage signal to obtain a sleeping posture detection signal that characterizes whether the sleeping posture is abnormal.

[0045] Furthermore, the auxiliary linear conversion circuit includes a ninth resistor, a tenth resistor, an eleventh resistor, an auxiliary bridge power supply terminal, and an auxiliary ground terminal. The auxiliary flexible pressure sensor, the ninth resistor, the tenth resistor, and the eleventh resistor constitute an auxiliary differential bridge structure. The auxiliary bridge power supply terminal and the auxiliary ground terminal are connected to a set of diagonal points on the bridge arms of the auxiliary differential bridge structure. The other set of diagonal points on the bridge arms of the auxiliary differential bridge structure are connected to the sleeping posture detection circuit.

[0046] The voltage at the power supply terminal of the auxiliary bridge is 3.3V, and the auxiliary grounding terminal is grounded.

[0047] Furthermore, the sleeping posture detection circuit includes:

[0048] The fourth operational amplifier has its non-inverting and inverting inputs connected to the other diagonal of the bridge arm in the auxiliary differential bridge structure. The positive power supply is connected to a 5V power supply, and the negative power supply is grounded.

[0049] The twelfth resistor has one end connected to the output terminal of the fourth operational amplifier and the other end connected to the microcontroller.

[0050] The thirteenth resistor has one end connected to the other end of the twelfth resistor, and the other end grounded.

[0051] Furthermore, it also includes:

[0052] The power supply circuit is connected to the main linear conversion circuit, the differential amplifier circuit, the second-order Butterworth low-pass filter circuit, the dual-T active notch filter circuit, the microcontroller, the auxiliary linear conversion circuit, and the sleeping posture detection circuit, respectively, and is used to supply power to the main linear conversion circuit, the differential amplifier circuit, the second-order Butterworth low-pass filter circuit, the dual-T active notch filter circuit, the microcontroller, the auxiliary linear conversion circuit, and the sleeping posture detection circuit.

[0053] Furthermore, the core chip in the microcontroller is an STM32F103C8T6.

[0054] The beneficial effects of this utility model are as follows: This wearable infant sleep monitoring device integrates a flexible pressure sensor with hardware circuitry, making it small, wearable, and capable of detecting various environments, thus offering portability. Furthermore, the device has a simple structure, low cost, and is easy to operate; most functions are implemented through hardware circuitry, allowing for the replacement of damaged components to meet the needs of different usage scenarios and user groups. Additionally, the flexible pressure sensor, fixed to the abdomen, collects respiratory signals with high sensitivity and minimal environmental interference. Moreover, suitable sensor models and resistance values ​​can be selected based on the infant's age, ensuring high individual adaptability. Attached Figure Description

[0055] Figure 1 This is a structural block diagram of a wearable infant sleep monitoring device according to the present invention;

[0056] Figure 2 This is a partial circuit diagram of a wearable infant sleep monitoring device according to the present invention;

[0057] Figure 3 This is a partial circuit diagram of a wearable infant sleep monitoring device according to the present invention;

[0058] Figure 4 This is a circuit diagram of the power supply circuit in a wearable infant sleep monitoring device according to the present invention.

[0059] Figure 5 This is a circuit diagram of the microcontroller in a wearable infant sleep monitoring device according to the present invention. Detailed Implementation

[0060] The principles and features of this utility model are described below with reference to the accompanying drawings. The examples given are only for explaining this utility model and are not intended to limit the scope of this utility model.

[0061] like Figure 1 As shown, a wearable infant sleep monitoring device includes:

[0062] The main flexible pressure sensor is used to sense the pressure signal generated by abdominal movement caused by sleep breathing as a first resistance signal;

[0063] The main linear conversion circuit, connected to the main flexible pressure sensor, forms a main differential bridge structure, used to perform linear conversion on the first resistance signal to obtain a first differential voltage signal containing common-mode interference;

[0064] A differential amplifier circuit, connected to the main linear conversion circuit, is used to suppress the common-mode interference and enhance the first differential-mode voltage signal to obtain an amplified signal;

[0065] A second-order Butterworth low-pass filter circuit is connected to the differential amplifier circuit to filter out high-frequency interference in the amplified signal and obtain a low-pass filtered signal.

[0066] A dual-T active notch filter circuit is connected to the second-order Butterworth low-pass filter circuit to filter out power frequency interference in the low-pass filter signal and obtain an electrical signal for characterizing sleep breathing.

[0067] A microcontroller, connected to the dual-T active notch filter circuit, is used to sample the electrical signal to achieve sleep breathing monitoring.

[0068] This invention discloses a wearable infant sleep monitoring device that integrates a flexible pressure sensor with hardware circuitry into a wearable device. It detects changes in resistance caused by the sensor's deformation due to abdominal movement during infant breathing. A main linear converter circuit converts these resistance changes into voltage changes. A differential amplifier circuit then performs common-mode interference suppression and signal enhancement. A second-order Butterworth low-pass filter circuit filters out high-frequency interference, and a dual-T active notch filter circuit filters out power frequency interference. Finally, a precise electrical signal characterizing sleep breathing is obtained. A microcontroller samples this signal and converts it into a digital signal using an ADC, which is then transmitted to a host computer via USB to achieve sleep breathing monitoring. This invention achieves high precision, miniaturization, intelligence, and ease of operation.

[0069] In some embodiments, the main flexible pressure sensor is a strip-shaped thin-film pressure sensor with a two-layer structure: the top layer consists of a flexible thin film and a pressure-sensitive layer laminated thereon, while the bottom layer consists of a flexible thin film and conductive lines laminated thereon. The two layers are bonded together with double-sided adhesive and the sensing area is isolated. When the sensing area is compressed, the disconnected lines on the bottom layer become conductive through the pressure-sensitive layer on the top layer, and the resistance output value at the port changes with the pressure; the greater the pressure, the lower the resistance. In use, the main flexible pressure sensor is fixed at the point of greatest abdominal deformation during infant breathing. The slight pressure exerted by the infant's abdomen during breathing causes a change in resistance within the sensor, allowing it to be used to detect infant sleep breathing signals.

[0070] In some embodiments, the main flexible pressure sensor is one or two.

[0071] When the main flexible pressure sensor is provided, the main linear conversion circuit includes three preset resistors, a main bridge power supply terminal and a main ground terminal. The main flexible pressure sensor and the three preset resistors form a main differential bridge structure. The main bridge power supply terminal and the main ground terminal are connected to a pair of diagonals of the bridge arms in the main differential bridge structure. The other pair of diagonals of the bridge arms in the main differential bridge structure are connected to the main linear conversion circuit.

[0072] When there are two main flexible pressure sensors, the main linear conversion circuit includes two preset resistors, a main bridge power supply terminal and a main ground terminal. The two main flexible pressure sensors and the two preset resistors are arranged in a cross manner to form a main differential bridge structure. The main bridge power supply terminal and the main ground terminal are connected to a set of diagonal points of the bridge arm in the main differential bridge structure. The other set of diagonal points of the bridge arm in the main differential bridge structure is connected to the main linear conversion circuit.

[0073] The voltage at the main bridge power supply terminal is 3.3V, and the main grounding terminal is grounded.

[0074] In practical use, the main flexible pressure sensor is installed on the infant's abdomen (according to research, infants mostly use abdominal breathing). When the infant breathes, the deformation of the abdomen generates a small pressure on the main flexible pressure sensor. The main flexible pressure sensor with the same trend of change is installed at the diagonal position of the bridge circuit, which can be converted into a voltage signal by the bridge circuit. According to theoretical analysis, the full bridge circuit has the best linearity and sensitivity (one or two main flexible pressure sensors can be placed according to the actual situation, and the other positions can be replaced with predetermined resistors. All of them can achieve the same function but have different linearity and sensitivity).

[0075] like Figure 2 As shown, in this embodiment, there are two main flexible pressure sensors, namely a first main flexible pressure sensor H1 and a second main flexible pressure sensor H2; the main linear conversion circuit includes two preset resistors, namely a first preset resistor R1' and a second preset resistor R2'. The resistance values ​​of the first preset resistor R1' and the second preset resistor R2' are 30KΩ, and the open-circuit resistance of both the first main flexible pressure sensor H1 and the second main flexible pressure sensor H2 is 30KΩ. Initially, the bridge remains balanced. Using a differential bridge instead of a single-arm bridge increases sensitivity by 100% and improves output linearity. According to the differential bridge circuit formula:

[0076]

[0077] Among them, R H1 and R H2ΔR represents the open-circuit resistance of the first main flexible pressure sensor H1 and the second main flexible pressure sensor H2, respectively. H1 and ΔR H2 These represent the changing resistances of the first main flexible pressure sensor H1 and the second main flexible pressure sensor H2, respectively.

[0078] Let R1' = R2' = R under the initial conditions. H1 =R H2 =R, which can be simplified and derived to show the relationship between ΔR (ΔR represents the change in input resistance in the main differential bridge structure) and output voltage U as follows:

[0079]

[0080] Therefore, the main linear conversion circuit converts changes in input resistance into changes in output voltage.

[0081] In some embodiments, such as Figure 2 As shown, the differential amplifier circuit includes:

[0082] The first operational amplifier U1, model INA333, has its VIN+ and VIN- pins connected to the main linear conversion circuit, its V+ pin connected to a 5V power supply, its V- and REF pins grounded, and its VOUT pin connected to the second-order Butterworth low-pass filter circuit.

[0083] The first resistor R1 is connected between the two RG pins of the first operational amplifier U1.

[0084] Specifically, since the input first differential voltage signal is weak and contains a large amount of common-mode interference, it is necessary to suppress common-mode interference, enhance the first differential voltage signal, and minimize interference and noise. Meanwhile, when no pressure is applied, the output signal difference of the main differential bridge is 0V, requiring the first operational amplifier U1 to handle signals close to 0V. Therefore, the first operational amplifier U1 is selected as the INA333 model, which has advantages such as ultra-high CMRR, single-supply operation, rail-to-rail output (close to 0V), low noise, and adjustable gain (adjusted by resistor R1).

[0085] The main flexible pressure sensor operates in the linear region of the INA333 within a 25-30KΩ range. The gain G1 of the first operational amplifier U1 can be calculated using the formula:

[0086]

[0087] Since the input signal voltage range of the microcontroller is 0 to 3.3V, the amplification factor cannot be too large. Therefore, the resistance of the first resistor R1 is 20KΩ, and G1 = 6 is calculated.

[0088] In some embodiments, such as Figure 2 As shown, the second-order Butterworth low-pass filter circuit includes:

[0089] The second resistor R2 is connected at one end to the differential amplifier circuit.

[0090] The third resistor R3 is connected at one end to the other end of the second resistor R2;

[0091] The second operational amplifier U2 has its non-inverting input terminal connected to the other end of the third resistor R3, its output terminal connected to the double-T active notch filter circuit, its positive power supply terminal connected to a 5V power supply, and its negative power supply terminal grounded.

[0092] The fourth resistor R4 is connected at one end to the inverting input terminal of the second operational amplifier U2, and at the other end to ground;

[0093] The fifth resistor R5 is connected between the inverting input terminal and the output terminal of the second operational amplifier U2;

[0094] The first capacitor C1 has one end connected to the non-inverting input terminal of the second operational amplifier U2, and the other end grounded;

[0095] The fifth capacitor C5 has one end connected between the second resistor R2 and the third resistor R3, and the other end connected to the output terminal of the second operational amplifier U2.

[0096] Specifically, the second operational amplifier U2 is an OPA365. The design of the second-order Butterworth low-pass filter circuit is based on the Butterworth filter principle, which refers to a filter with a flat response within its passband. A second-order Butterworth low-pass filter circuit is characterized by a relatively gentle transition band at the cutoff frequency, effectively filtering out high-frequency noise while retaining low-frequency signals. In the second-order Butterworth low-pass filter circuit, the order is 2, thus achieving a relatively steep filter characteristic. An infant's respiratory rate is approximately 0.5–1Hz, requiring the filtering of high-frequency interference. Using the high-precision, low-noise, rail-to-rail input / output, single-supply operational amplifier OPA365 achieves better filtering results. The resistances of the second resistor R2, third resistor R3, and fourth resistor R4 are 16KΩ; the resistance of the fifth resistor R5 is 8.06KΩ; and the capacitances of the first capacitor C1 and the fifth capacitor C5 are 1uF. According to the formula... Find the cutoff frequency f 截止 =10Hz; the second resistor R2, the fourth resistor R4, the first capacitor C1, and the fifth capacitor C5 work together to adjust the amplitude-frequency response of the second-order Butterworth low-pass filter circuit, ensuring a flat passband and a steep stopband attenuation. The amplification factor G2 of the second operational amplifier U2 is:

[0097]

[0098] In some embodiments, such as Figure 2 As shown, the dual-T active notch filter circuit includes:

[0099] The sixth resistor R6 is connected at one end to the second-order Butterworth low-pass filter circuit.

[0100] The seventh resistor R7 is connected at one end to the other end of the sixth resistor R6;

[0101] The second capacitor C2 is connected at one end to one end of the sixth resistor R6;

[0102] The third capacitor C3 has one end connected to the other end of the second capacitor C2 and the other end connected to the other end of the seventh resistor R7.

[0103] The eighth resistor R8 has one end connected between the second capacitor C2 and the third capacitor C3, and the other end grounded;

[0104] The fourth capacitor C4 has one end connected between the sixth resistor R6 and the seventh resistor R7, and the other end grounded.

[0105] The third operational amplifier U3 has its non-inverting input connected to the other end of the seventh resistor R7, its positive power supply connected to a 5V power supply, its negative power supply grounded, its inverting input connected to the output, and its output connected to the microcontroller.

[0106] Specifically, the double-T active notch filter circuit is used to filter out interference from the 50Hz power frequency signal. Resistors R7 and R8 have a resistance of 11KΩ, and resistor R9 has a resistance of 5.49KΩ; capacitors C2 and C3 have a capacitance of 0.33uF, and capacitor C4 has a capacitance of 0.68uF. According to the formula: Find the cutoff frequency f 截止 =50Hz; the values ​​of each component in the dual-T network satisfy the following relationships: C2=C3=C, C4=2C, R6=R7=R, R8=1 / 2R. A third operational amplifier U3 is added to the dual-T network to form an active notch filter circuit, thereby improving frequency selection, providing feedback loop gain, and isolating the dual-T network.

[0107] In some embodiments, such as Figure 1 As shown, the wearable infant sleep monitoring device of this utility model also includes:

[0108] A flexible pressure sensor is used to detect the pressure signal generated by lying face down as a second resistance signal;

[0109] An auxiliary linear conversion circuit, connected to the auxiliary flexible pressure sensor to form an auxiliary differential bridge structure, is used to linearly convert the second resistance signal to obtain a second differential voltage signal used to characterize sleeping posture.

[0110] The sleeping posture detection circuit, connected to the auxiliary linear conversion circuit and the microcontroller, is used to compare the second differential voltage signal to obtain a sleeping posture detection signal that characterizes whether the sleeping posture is abnormal.

[0111] Specifically, an auxiliary flexible pressure sensor, an auxiliary linear conversion circuit, and a sleeping posture detection circuit collect infant sleeping posture signals, and the output signal represents whether the sleeping posture is abnormal and is connected to the microcontroller.

[0112] The flexible pressure sensor used for detecting sleeping posture also employs a flexible thin-film pressure sensor, specifically an RP-C series circular sensor. Its structure and principle are the same as the sensor used for respiratory detection. When measuring sleeping posture, it is also fixed to the infant's abdomen (to avoid inaccuracies from other locations). However, the fixed positions of the respiratory and sleeping posture sensors do not overlap (to avoid mutual interference). The accuracy requirement for the fixed position of the respiratory sensor is higher than that of the sleeping posture sensor; the respiratory sensor is fixed at the location of maximum abdominal deformation, while the sleeping posture sensor only needs to be attached to a location that can detect pressure from prone sleeping.

[0113] In some embodiments, such as Figure 3 As shown, the auxiliary linear conversion circuit includes a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, an auxiliary bridge power supply terminal, and an auxiliary ground terminal. The auxiliary flexible pressure sensor H3, the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11 constitute an auxiliary differential bridge structure. The auxiliary bridge power supply terminal and the auxiliary ground terminal are connected to a pair of diagonal points on the bridge arms of the auxiliary differential bridge structure. The other pair of diagonal points on the bridge arms of the auxiliary differential bridge structure are connected to the sleeping posture detection circuit.

[0114] The voltage at the power supply terminal of the auxiliary bridge is 3.3V, and the auxiliary grounding terminal is grounded.

[0115] The sleeping posture detection circuit includes:

[0116] The fourth operational amplifier U4 has its non-inverting and inverting inputs connected to the other diagonal of the bridge arm in the auxiliary differential bridge structure. The positive power supply is connected to a 5V power supply, and the negative power supply is grounded.

[0117] The twelfth resistor R12 is connected at one end to the output terminal of the fourth operational amplifier U4 and at the other end to the microcontroller;

[0118] The thirteenth resistor R13 has one end connected to the other end of the twelfth resistor R12, and the other end grounded.

[0119] Specifically, the resistances of resistors R9, R10, R11, R12, and R13 are all 10KΩ, and the open-circuit resistance of the auxiliary flexible pressure sensor H3 is 30KΩ. The fourth operational amplifier U4, model LM8261, features high output current and high speed, making it suitable for constructing precision switching circuits. When the infant sleeps on their stomach, the auxiliary flexible pressure sensor H3 experiences increased pressure to a specific value, outputting a signal indicating an abnormal sleeping posture.

[0120]

[0121] V+ and V- represent the second differential voltage signal; when V+ is greater than V-, the output is 5V; when V+ is less than V-, the output is 0V. The output signal V of the fourth operational amplifier U4 is divided by the twelfth resistor R12 and the thirteenth resistor R13 to obtain the voltage-divided signal Vo:

[0122]

[0123] The voltage divider signal is transmitted to the microcontroller. When the signal reaches the preset input value range of the microcontroller, an abnormal sleeping posture can be determined.

[0124] In some embodiments, the wearable infant sleep monitoring device of the present invention further includes:

[0125] The power supply circuit is connected to the main linear conversion circuit, the differential amplifier circuit, the second-order Butterworth low-pass filter circuit, the dual-T active notch filter circuit, the microcontroller, the auxiliary linear conversion circuit, and the sleeping posture detection circuit, respectively, and is used to supply power to the main linear conversion circuit, the differential amplifier circuit, the second-order Butterworth low-pass filter circuit, the dual-T active notch filter circuit, the microcontroller, the auxiliary linear conversion circuit, and the sleeping posture detection circuit.

[0126] Specifically, such as Figure 4As shown, the power supply circuit consists of a USB interface chip USBC1, a fifteenth resistor R15, a sixteenth resistor R16, a switch SW1, a DC-DC power isolation module, and a 5V-3.3V voltage conversion module. The USB interface chip USBC1 is a TYPE-C-31-M-12, used to provide VCC+5V power and transmit signals. Pins A4 and B9 of the USB interface chip USBC1 output VCC+5V power, and pins A1 and B12 are grounded. Pins A6 and A7 of the USB interface chip USBC1 are connected to the microcontroller. One end of the fifteenth resistor R15 is connected to pin B5 of the USB interface chip USBC1, and the other end is grounded. One end of the sixteenth resistor R16 is connected to pin A5 of the USB interface chip USBC1, and the other end is grounded. The switch SW1 is a slide switch of model SS-3235S-L1, with one pin connected to the VCC+5V power supply and the other three pins grounded. The resistance values ​​of the fifteenth resistor R15 and the sixteenth resistor R16 are both 5.1KΩ.

[0127] like Figure 4 As shown, the DC-DC power isolation module consists of chip U5, eleventh capacitor C11, and sixth capacitor C6. Chip U5 is model B0505S. The -Vin and -Vout pins of chip U5 are grounded, the +Vin pin is connected to VCC +5V power supply, and the +Vout pin outputs 5V power supply. The eleventh capacitor C11 is connected between the -Vin and +Vin pins of chip U5. The sixth capacitor C6 is connected between the -Vout and +Vout pins of chip U5. The capacitance of the eleventh capacitor C11 is 4.7uF, and the capacitance of the sixth capacitor C6 is 10uF.

[0128] like Figure 4 As shown, the 5V-3.3V voltage conversion module is used to realize ADC conversion and data transmission. It consists of chip U6, capacitors C7-C10, fourteenth resistor R14, and LED1. The chip U6 is model AMS1117-3.3. The ADJ pin of chip U6 is grounded, the VOUT pin is connected to the TAB pin, the VIN pin is connected to the 5V power supply, and the TAB pin outputs 3.3V power. One end of the seventh capacitor C7 and the eighth capacitor C8 is connected to the VIN pin of chip U6, and the other end is grounded. One end of the ninth capacitor C9 and the tenth capacitor C10 is connected to the TAB pin of chip U6, and the other end is grounded. One end of the fourteenth resistor R14 is connected to the TAB pin of chip U6, and the other end is connected to the positive terminal of LED1. The negative terminal of LED1 is grounded. The capacitance of the seventh capacitor C7 and the tenth capacitor C10 is 10uF, the capacitance of the eighth capacitor C8 and the ninth capacitor C9 is 100nF, and the capacitance of the fourteenth resistor R14 is 10KΩ.

[0129] In some embodiments, the core chip in the microcontroller is an STM32F103C8T6.

[0130] Specifically, such as Figure 5 As shown, the microcontroller circuit module consists of a core chip U7, twelfth capacitor C12 to twentieth capacitor C20, seventeenth resistor R17, first crystal oscillator X1, and second crystal oscillator X2. The signal source for the core chip U7 is an STM32F103C8T6. The PA0-WKUP pins of the core chip U7 are connected to the output of the dual-T active notch filter circuit. The PA1 pin of the core chip U7 is connected to the output of the sleeping posture detection circuit. The PA11 pin of the core chip U7 is connected to the A7 pin of the USB interface chip USBC1. The PA12 pin of the core chip U7 is connected to the USB interface... Pin A6 of chip USBC1 is connected; one end of the seventeenth resistor R17 is connected to the 3.3V power supply, and the other end is connected to pin PA12 of core chip U7; one end of the second crystal oscillator X2 is connected to pin PC14-OSC32_IN of core chip U7, and the other end is connected to pin PC145-OSC32_OUT of core chip U7; one end of the sixteenth capacitor C16 is connected to pin PC14-OSC32_IN of core chip U7, and the other end is grounded; one end of the seventeenth capacitor C17 is connected to pin PC145-OSC32_OUT of core chip U7. One end of the first crystal oscillator X1 is connected to the PD0-OSC_IN pin of the core chip U7, and the other end is connected to the PD1-OSC_OUT pin of the core chip U7; one end of the eighteenth capacitor C18 is connected to the PD0-OSC_IN pin of the core chip U7, and the other end is grounded; one end of the nineteenth capacitor C19 is connected to the PD1-OSC_OUT pin of the core chip U7, and the other end is grounded; one end of the twentieth capacitor C20 and the twelfth capacitor C12 are grounded and both are connected to the VSSA pin of the core chip U7, and the other end is connected to a 3.3V power supply. The thirteenth capacitor C13 is connected to the VDDA pin of the core chip U7; one end of the thirteenth capacitor C13 is grounded and connected to the VSS_1 pin of the core chip U7, and the other end is connected to the 3.3V power supply and the VDD_1 pin of the core chip U7; one end of the fourteenth capacitor C14 is grounded and connected to the VSS_3 pin of the core chip U7, and the other end is connected to the 3.3V power supply and the VDD_3 pin of the core chip U7; one end of the fifteenth capacitor C15 is grounded and connected to the VSS_2 pin of the core chip U7, and the other end is connected to the 3.3V power supply and the VDD_2 pin of the core chip U7.

[0131] like Figure 5As shown, the first crystal oscillator X1 is 8MHz, and the second crystal oscillator X2 is 32.768kHz, providing high-frequency and low-frequency clock signals for the core chip U7, respectively; the twentieth capacitor C20 has a capacitance of 10uF, the twelfth capacitors C12 to C15 have a capacitance of 0.1uF, the sixteenth capacitors C16 and C17 have a capacitance of 22pF, and the eighteenth capacitors C18 and C19 have a capacitance of 33pF; the seventeenth resistor R17 is a pull-up resistor with a resistance of 1.5KΩ.

[0132] The main function of the microcontroller is to acquire two signals (the circuit signal where the main flexible pressure sensor is located and the circuit signal where the auxiliary flexible pressure sensor is located), perform ADC conversion, and transmit data via USB 2.0 (transmitting the respiratory signal to the host computer for further visualization, analysis and diagnosis).

[0133] This utility model discloses a wearable infant sleep monitoring device that integrates a flexible pressure sensor with hardware circuitry. It is small, wearable, and capable of detecting sleep in various environments, making it highly portable. Furthermore, the device boasts a simple structure, low cost, and ease of operation. Most functions are implemented through hardware circuitry, allowing for the replacement of damaged components to meet the needs of different usage scenarios and user groups. The flexible pressure sensor, fixed to the abdomen, collects respiratory signals with high sensitivity and minimal susceptibility to environmental interference. Additionally, suitable sensor models and resistance values ​​can be selected based on the infant's age, ensuring high individual adaptability.

[0134] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A wearable infant sleep monitoring device, characterized in that, include: The main flexible pressure sensor is used to sense the pressure signal generated by abdominal movement caused by sleep breathing as a first resistance signal; The main linear conversion circuit, connected to the main flexible pressure sensor, forms a main differential bridge structure, used to perform linear conversion on the first resistance signal to obtain a first differential voltage signal containing common-mode interference; A differential amplifier circuit, connected to the main linear conversion circuit, is used to suppress the common-mode interference and enhance the first differential-mode voltage signal to obtain an amplified signal; A second-order Butterworth low-pass filter circuit is connected to the differential amplifier circuit to filter out high-frequency interference in the amplified signal and obtain a low-pass filtered signal. A dual-T active notch filter circuit is connected to the second-order Butterworth low-pass filter circuit to filter out power frequency interference in the low-pass filter signal and obtain an electrical signal for characterizing sleep breathing. A microcontroller, connected to the dual-T active notch filter circuit, is used to sample the electrical signal to achieve sleep breathing monitoring.

2. The wearable infant sleep monitoring device according to claim 1, characterized in that, The main flexible pressure sensor is one or two; When the main flexible pressure sensor is provided, the main linear conversion circuit includes three preset resistors, a main bridge power supply terminal and a main ground terminal. The main flexible pressure sensor and the three preset resistors form a main differential bridge structure. The main bridge power supply terminal and the main ground terminal are connected to a pair of diagonals of the bridge arms in the main differential bridge structure. The other pair of diagonals of the bridge arms in the main differential bridge structure are connected to the main linear conversion circuit. When there are two main flexible pressure sensors, the main linear conversion circuit includes two preset resistors, a main bridge power supply terminal and a main ground terminal. The two main flexible pressure sensors and the two preset resistors are arranged in a cross manner to form a main differential bridge structure. The main bridge power supply terminal and the main ground terminal are connected to a set of diagonal points of the bridge arm in the main differential bridge structure. The other set of diagonal points of the bridge arm in the main differential bridge structure is connected to the main linear conversion circuit. The voltage at the main bridge power supply terminal is 3.3V, and the main grounding terminal is grounded.

3. The wearable infant sleep monitoring device according to claim 1, characterized in that, The differential amplifier circuit includes: The first operational amplifier, model INA333, has its VIN+ and VIN- pins connected to the main linear conversion circuit, its V+ pin connected to a 5V power supply, its V- and REF pins grounded, and its VOUT pin connected to the second-order Butterworth low-pass filter circuit. The first resistor is connected between the two RG pins of the first operational amplifier.

4. The wearable infant sleep monitoring device according to claim 1, characterized in that, The second-order Butterworth low-pass filter circuit includes: The second resistor is connected at one end to the differential amplifier circuit. The third resistor is connected at one end to the other end of the second resistor; The second operational amplifier has its non-inverting input connected to the other end of the third resistor, its output connected to the double-T active notch filter circuit, its positive power supply connected to a 5V power supply, and its negative power supply grounded. The fourth resistor has one end connected to the inverting input of the second operational amplifier and the other end grounded. The fifth resistor is connected between the inverting input and output terminals of the second operational amplifier. The first capacitor has one end connected to the non-inverting input terminal of the second operational amplifier, and the other end grounded. The fifth capacitor has one end connected between the second resistor and the third resistor, and the other end connected to the output terminal of the second operational amplifier.

5. The wearable infant sleep monitoring device according to claim 1, characterized in that, The dual-T active notch filter circuit includes: The sixth resistor is connected at one end to the second-order Butterworth low-pass filter circuit. The seventh resistor is connected at one end to the other end of the sixth resistor; The second capacitor is connected at one end to one end of the sixth resistor; The third capacitor has one end connected to the other end of the second capacitor and the other end connected to the other end of the seventh resistor. The eighth resistor has one end connected between the second capacitor and the third capacitor, and the other end grounded. The fourth capacitor has one end connected between the sixth and seventh resistors, and the other end grounded. The third operational amplifier has its non-inverting input connected to the other end of the seventh resistor, its positive power supply connected to a 5V power supply, its negative power supply grounded, its inverting input connected to the output, and its output connected to the microcontroller.

6. The wearable infant sleep monitoring device according to claim 1, characterized in that, Also includes: A flexible pressure sensor is used to detect the pressure signal generated by lying face down as a second resistance signal; An auxiliary linear conversion circuit, connected to the auxiliary flexible pressure sensor to form an auxiliary differential bridge structure, is used to linearly convert the second resistance signal to obtain a second differential voltage signal used to characterize sleeping posture. The sleeping posture detection circuit, connected to the auxiliary linear conversion circuit and the microcontroller, is used to compare the second differential voltage signal to obtain a sleeping posture detection signal that characterizes whether the sleeping posture is abnormal.

7. The wearable infant sleep monitoring device according to claim 6, characterized in that, The auxiliary linear conversion circuit includes a ninth resistor, a tenth resistor, an eleventh resistor, an auxiliary bridge power supply terminal, and an auxiliary ground terminal. The auxiliary flexible pressure sensor, the ninth resistor, the tenth resistor, and the eleventh resistor constitute an auxiliary differential bridge structure. The auxiliary bridge power supply terminal and the auxiliary ground terminal are connected to a pair of diagonals of the bridge arms in the auxiliary differential bridge structure. The other pair of diagonals of the bridge arms in the auxiliary differential bridge structure are connected to the sleeping posture detection circuit. The voltage at the power supply terminal of the auxiliary bridge is 3.3V, and the auxiliary grounding terminal is grounded.

8. The wearable infant sleep monitoring device according to claim 7, characterized in that, The sleeping posture detection circuit includes: The fourth operational amplifier has its non-inverting and inverting inputs connected to the other diagonal of the bridge arm in the auxiliary differential bridge structure. The positive power supply is connected to a 5V power supply, and the negative power supply is grounded. The twelfth resistor has one end connected to the output terminal of the fourth operational amplifier and the other end connected to the microcontroller. The thirteenth resistor has one end connected to the other end of the twelfth resistor, and the other end grounded.

9. The wearable infant sleep monitoring device according to claim 6, characterized in that, Also includes: The power supply circuit is connected to the main linear conversion circuit, the differential amplifier circuit, the second-order Butterworth low-pass filter circuit, the dual-T active notch filter circuit, the microcontroller, the auxiliary linear conversion circuit, and the sleeping posture detection circuit, respectively, and is used to supply power to the main linear conversion circuit, the differential amplifier circuit, the second-order Butterworth low-pass filter circuit, the dual-T active notch filter circuit, the microcontroller, the auxiliary linear conversion circuit, and the sleeping posture detection circuit.

10. The wearable infant sleep monitoring device according to claim 1, characterized in that, The core chip in the microcontroller is an STM32F103C8T6.

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