Medical Sensor Monitor

A small embedded system that reads body temperature and heart rate, displays them live on an LCD, and logs the data for analysis on a PC.

I built this to get hands-on with biomedical sensing and embedded systems — two areas I want to develop as I go deeper into electrical engineering. It's also my first real attempt at wiring analogue sensors together with a microcontroller, so a lot of this was figuring things out as I went.

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What It Does

• Reads body temperature using an LM35 analogue sensor
• Detects heart rate in BPM using a KY-039 pulse sensor
• Displays both readings live on a 16×2 I2C LCD
• Streams data as CSV over USB serial for PC logging
• Includes a Python script to plot and review recorded sessions

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Demo

=== Medical Sensor Monitor ===
Time(ms), Temp(C), BPM
1002, 36.8, 0
2004, 36.9, 72
3006, 36.8, 74

LCD display:

Temp: 36.8°C
HR:   73 BPM

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Hardware

Component	Purpose
Arduino Uno	Microcontroller
LM35	Analogue temperature sensor (10mV/°C)
KY-039	Optical pulse sensor
16×2 I2C LCD	Live display
Breadboard + jumper wires	Prototyping

Full wiring and pin connections are in docs/wiring.md.

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Getting Started

Upload to Arduino

• Install LiquidCrystal_I2C from the Arduino Library Manager
• Open src/med_sensor_monitor.ino
• Select your board and port, then upload

Log Data to PC

pip install pyserial
python src/serial_logger.py --port COM3 --duration 60

Plot the Data

pip install pandas matplotlib
python src/analyse.py --file log_20260101_120000.csv

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Project Structure

med-sensor-monitor/
├── src/
│   ├── med_sensor_monitor.ino
│   ├── serial_logger.py
│   └── analyse.py
├── docs/
│   └── wiring.md
└── README.md

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What I Learned

This project pushed me to understand things I hadn't dealt with before. A few that stood out:

• How analogue sensors work and how to convert raw voltage readings into meaningful units
• Writing a peak detection algorithm to extract BPM from a noisy analogue signal — this took more tuning than I expected
• How the I2C protocol works and why it's useful for keeping wiring clean
• Bridging Arduino and Python over serial, and building a simple data pipeline from sensor to CSV to graph

The gap between "it compiles" and "it actually works reliably" was where most of the learning happened.

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What I Want to Add

• SD card logging to remove the dependency on a PC
• OLED display for a sharper, more compact UI
• Moving average filter to smooth out noisy BPM readings
• Threshold alerts via buzzer for abnormal temperature or heart rate
• Bluetooth module (HC-05) for wireless data transmission

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About

Engineering Product Design, SUTD Interests: Electrical Engineering · Healthcare Technology · Embedded Systems

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For learning purposes only — not a certified medical device.