The intelligent sphygmomanometer has low cost, miniaturization and automation, and has developed into an important intelligent terminal at home. Users can use their spare time for physical examination. The new intelligent electronic sphygmomanometer scheme can effectively realize the wireless network transmission of measurement data, record the blood pressure parameter values, and display the historical measurement records, so that users can timely understand their physical conditions, and carry out prevention and treatment as early as possible, thus preventing and treating hypertension more effectively.
The electronic sphygmomanometer mostly uses the oscilloscope method, and uses the inflatable cannula in the measurement process to block the blood flow of the upper arm artery. Due to the hemodynamics of the heart, the pressure wave on the cuff overlaps with the synchronized pressure wave of the heart, which is called a pulse wave.
When the cuff pressure is higher than the systolic pressure, the pulse wave disappears. As the pressure on the cuff decreases, pulse waves begin to appear. When the cuff pressure changes from above systolic blood pressure to below systolic blood pressure, the pulse wave suddenly increases. When the pressure drops to the average pressure, the pulse wave reaches its maximum. Then it decays as the cuff pressure decreases.
The oscillographic method for measuring blood pressure can estimate and control blood pressure based on the relationship between pulse wave amplitude and sleeve pressure management in the era. Pulse wave amplitude and corresponding average blood pressure. Systolic and diastolic blood pressure are determined by the ratio of the maximum different amplitudes of pulse waves in the market,PmIs the average pressure,PsFor systolic blood pressure,PdIs diastolic blood pressure,UmIs the maximum pulse wave amplitude,KsandKdThe correlation coefficient between systolic and diastolic blood pressure without corresponding pulse signal amplitude and the average pressure amplitude ratio of corresponding pulse waves,KsandKdThe manufacturer of sphygmomanometer shall generally select it according to the experience value.
Hardware of sphygmomanometer scheme
use rl78/l1aAs the main microcontroller,flash romSize is96kb，ramSize is5.5 kb。 exceptrl78/l1aBesides the microcontroller, there is also a display boardrl78/g1db leMicrocontroller module and peripheral circuits(LCD display, blood pressure measurement circuit, pressure control circuit)。
Part of the power supply is supplied byfoursectionAAADry batteries andDC 6VPower input power supply. switchSW2After connection, the intelligent sphygmomanometer is powered on,6VVoltage is regulated by a voltage regulator chipXC6206-3.3VStabilize voltage to3.3VsupplyMCUWait for peripheral devices, while passingA\\u002FDThe port samples the battery voltage.6VThe voltage directly supplies power to the inflator and solenoid valve.
The pressure and sensors that can be used in this application areABPDANN005PG2A3The pressure passes through the sensor. The pressure sensor has12-bitofI2CDigital culture output has a high precision and good linearity. The working range of pressure control measurement is0~5psiThe corresponding blood pressure value is approximately0~258mmHg, and the design and development of sphygmomanometer require enterprises to match.
The control circuit of the air pump and solenoid valve adoptsNPNType triodeDTC114andPChannelMOSFET（IRLML6402）Composition,DTC114andIRLML6402have1MHzThe above switch speeds are suitable for high speedsPWMControl. Air pump usageMITSUMICompany'sMAP-AM-265The rated voltage is6VThe maximum pressure can reach400mmHg。 Selection of solenoid valvesKSV05B，6VPower supply, pressure from300mmHgReduce to15mmHgOnly requiredthreeSeconds.
The display section is composed offourpositioneightThe segment LCD display is complete.Rl78/l1aThe microcontroller is equipped with4 ~ 8Channel pins and28 ~ 32Channel pins can independently drive and control the LCD display.
LEDThe control circuit is composed ofNPNComposed of a transistor and a current limiting resistor, it is used to indicate the currentLCDWhat parameters are displayed.LED0(red)Denotes systolic blood pressure,LED1(yellow)Denotes diastolic blood pressure,LED2(blue)Indicates pulse.
Schematic diagram andBOM
The sphygmomanometer case integrates a Bluetooth control module on an ordinary electronic sphygmomanometer, and uses Bluetooth technology to realize the function of wireless network transmission system. In order to achieve our research application, we need to burn and write separatelyBLEProgram and application analysis program toRL78/G1DModule andRL78/L1AAnd install it accordinglyAPPreachAndroidDeveloping smartphones throughBLEThe function can realize the communication between your mobile phone and the intelligent sphygmomanometer. Smartphone information receives systolic pressure, diastolic pressure and pulse data from the sphygmomanometer, displays and stores management data.
intelligencebomindicate,bomThere are substitutes for the components of. Due to the internal characteristics of different microcontrollersromUnlike parameters, the eigenvalues, noise, and power consumption of the system also differ. When replacing the crystal oscillator, attention should be paid to the corresponding capacitance of the two loadsc9andc10It may also need to be replaced