What is vital-signs-monitor?

This project is a portable medical monitoring device built from scratch as a biomedical engineering bachelor's thesis project. It measures four vital signs at once, heart rhythm, blood oxygen level, body temperature, and breathing rate, reproducing the core functions of a hospital patient monitor using affordable, accessible electronic parts. It is a working proof of concept the author built and tested, not a certified medical device that could be used for real patient care. The device runs on an ESP32 microcontroller, a small dual core chip that runs the whole system. Heart activity is picked up with a chest sensor and turned into a heartbeat reading using a well known heartbeat detection method, which the author tested against a large public database of real heart recordings and found to correctly identify almost 99 percent of heartbeats. Blood oxygen and breathing rate come from a single optical sensor placed against the skin, temperature comes from a separate digital sensor, and all the readings are shown on a small screen built into the device as well as on a webpage you can open over the device's own WiFi signal. It also has a three level alarm system with lights and a buzzer, and it saves session data with timestamps onto a memory card. Everything, including the circuit design, a parts list with costs, and a 3D printable case, is included in the repository alongside the author's thesis document. The software is written in C++ using FreeRTOS, a system that lets several tasks run at once across the chip's two processor cores, so that things like reading sensors and updating the display do not interfere with each other. The project is aimed at students, hobbyists, or researchers interested in medical device engineering rather than people looking for a certified clinical product. It is released under the MIT license.