Sunday, February 25, 2024

Smart Blood Pressure Monitor Reference Design

By Nidhi Agarwal

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A pressure monitor measures blood pressure and pulse, syncing data with a smartphone app, utilizing specific modules, and employing an oscillometric method for measurement.

BP monitor

The electronic blood pressure monitor, characterized by its affordability, compact size, and automated operation, has emerged as a vital healthcare device for households. It offers simplicity in usage and portability. In tandem with the advancements in smartphone and mobile internet technology, smart blood pressure monitors now enable wireless data transmission and parameter recording for blood pressure values.

The Smart Blood Pressure Monitor reference design by Renesas allows for convenient checking of systolic, diastolic, and pulse rates. It displays results and battery status on an LCD screen and a smartphone app. The measurement process starts with a simple button press. The RL78/L1A ultra-low power consumption LCD MCU supports multiple sensors and syncs data to your smartphone through the RL78/G1D MCU’s BLE function, reducing overall costs with its integrated peripheral functions.

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The demo board comprises the RL78/L1A and RL78/G1D modules, while the peripheral board includes components like an LCD, blood pressure measurement circuit, and air pressure control circuit. The RL78/L1A boasts a 96KB Flash ROM and 5.5KB RAM size. Users can connect to the Smart Blood Pressure Monitor via a smartphone app, utilizing its built-in Bluetooth module. Power can be supplied either by four AAA batteries or a DC 6V input.

The pressure sensor features a 12-bit digital I2C output with high accuracy and linearity. The LED control circuit employs NPN digital transistors and current limitation resistors to indicate displayed parameters on the LCD. The blood pressure measurement utilizes the oscillometric method and can be initiated by pressing the “Start/Stop” key or the “Start Measurement” button on the app. The smart blood pressure monitor app can access Historical measurement records through the “History” button.

The smart blood pressure monitor initiates the measurement by pressing the “Start/Stop” key or the “Start measurement” button on the smart blood pressure monitor app (inactive during measurement). Initially, pressure is applied to the arm cuff, with the solenoid valve closed during pressurization. An air pump controlled by PWM is used for inflating the arm cuff. Once the pressure reaches the preset value (typically 160mmHg), the pressurization halts, and a linear deflation process begins. During deflation, the smart blood pressure monitors sample data and performs calculations. Subsequently, the LCD systolic pressure, diastolic pressure, and pulse data were sequentially. If you wish to stop the measurement during the process, press the “Start/Stop” button again, causing the quick-release solenoid valve to open and release the air from the arm cuff.

Renesas has tested this reference design. It comes with a Bill of Material (BOM), schematics, etc. You can find additional data about the reference design on the company’s website. To read more about this reference design, click here.

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