Design and Implementation of a Low-Cost IoT-Enabled Smartwatch for Monitoring Patient Health
Keywords:
Internet of Things; wearable health monitoring; photoplethysmography; MAX30102; low-cost smartwatch; pulse oximetry; SpO₂.Abstract
Continuous monitoring of vital signs is central to preventive healthcare and chronic-disease management, yet commercial smartwatches from manufacturers such as Apple, Fitbit, and Samsung remain prohibitively expensive for most users in developing countries, with prices in Nigeria ranging from roughly ₦340,000 to ₦1,200,000. This creates a significant accessibility gap in personal health technology. This work presents the design, implementation, and validation of a low-cost, Internet of Things (IoT)-enabled smartwatch capable of real-time monitoring of blood oxygen saturation (SpO₂), heart rate, and body temperature. The prototype integrates a MAX30102 pulse-oximetry and heart-rate sensor, a DS18B20 digital temperature sensor, and an ATmega328P microcontroller, together with a DS3231 real-time clock, an HC-06 Bluetooth module, and an SSD1306 OLED display. A three-stage power tree (TP4056 charge controller, MCP1700 low-dropout regulator, and MOSFET-based peripheral load switching) manages the rechargeable lithium-polymer battery. Firmware developed in the Arduino IDE implements peak-detection heart-rate estimation, ratio-of-ratios SpO₂ calculation with local calibration, and a signal-quality gate that withholds unreliable readings rather than reporting them. The device was validated against medical-grade reference instruments (Masimo MightySat, Polar H10, Braun tympanic thermometer) across 1,440 paired SpO₂ and heart-rate samples and 120 paired temperature samples from 20 participants, with usability assessed by 30 additional respondents. The prototype achieved an SpO₂ accuracy of 1.78% ARMS (mean absolute error 1.62%), a combined heart-rate mean absolute error of 2.58 bpm, and a temperature mean absolute error of 0.31 °C, meeting the ISO 80601-2-61 clinical threshold and comparing favourably with flagship consumer devices costing more than ten times as much. Aggressive duty cycling extended battery life from 17.4 h in continuous-monitoring mode to 102 h in power-saving mode. These results demonstrate that careful engineering of commodity components, rather than exotic hardware, is the binding constraint on affordable, clinically credible wearable health monitoring.
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