Project Hub /Healthcare Biomedical & Assistive/Pulse Oximeter & Vital Scanner/Designing a Smartwatch using ESP32 Part 2 - Ambient Light and Heart Rate Sensors

Intermediate

ESP32

Project Specific

3 – 6 Hours

Partial Kit

Designing a Smartwatch using ESP32 Part 2 - Ambient Light and Heart Rate Sensors

This project guides you through interfacing the BH1750 ambient light sensor and the MAX30102 heart rate sensor with an ESP32 microcontroller as part of a DIY smartwatch build.

Originally published on CircuitDigest

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

ESP32 WiFi+Bluetooth CP2102 Development Board Rs. 520.00
LDR Light Sensor Module Rs. 49.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

We don't carry yet: Pulse / Heart Rate Sensor
TFT / Touch LCD

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How It Works

This wearable prototype centers around the ESP32 DevKit v1 microcontroller, which coordinates data acquisition and visual output. To monitor health and environment, the system integrates two key digital sensors communicating via the I2C protocol. The MAX30102 module uses integrated red and infrared LEDs alongside photodetectors to measure blood oxygen saturation (SpO2) and heart rate via photoplethysmography (PPG) at the user's fingertip or wrist. Simultaneously, the BH1750 ambient light sensor measures surrounding illumination levels, returning a calibrated lux value that allows the system to gauge external lighting conditions. The ESP32 processes these incoming sensor metrics and drives a full-color TFT display (using the ST7789 driver chip) to render real-time health statistics and environmental readouts. Power distribution, signal routing, and temporary prototyping are managed through a breadboard and jumper wires, while the Arduino IDE compiles and uploads the necessary software libraries—including dedicated drivers for the display, light sensor, and pulse oximeter—to execute the firmware loop.

Why Build This

Gain hands-on experience integrating multiple I2C peripheral sensors onto a single microcontroller bus for biomedical and environmental data logging.

Develop practical firmware skills by combining complex hardware drivers—such as optical pulse oximetry and graphical display rendering—into a cohesive embedded application.

Explore the engineering principles behind consumer wearable technology, including adaptive user interface brightness and continuous vital sign monitoring.

Real-World Application

Wearable health monitoring devices, smart fitness bands, and adaptive display brightness control in consumer electronics.

Skills You'll Learn

I2C serial communication

sensor data processing

optical biosensing principles

SPI display interfacing

embedded firmware architecture

Safety Precautions

No specific precautions noted for this build — always follow general electronics safety practices.

Technology Tags

ESP32

BH1750

MAX30102

I2C

SPI

TFT_ESPI

SENSORS

WEARABLES

ARDUINO

Frequently Asked Questions

Can I power this entire smartwatch setup directly from a standard USB connection?

Yes, powering the ESP32 DevKit v1 via USB supplies stable 5V and 3.3V rails capable of driving the microcontroller, sensors, and TFT display during desktop prototyping.

Why are there multiple sensor libraries required in the Arduino IDE?

The BH1750 and MAX30102 use different internal registers and communication protocols; dedicated libraries abstract these complexities so you can easily query lux, heart rate, and SpO2 values without writing low-level byte-parsing code.

How do the MAX30102 and BH1750 share the same microcontroller pins?

Both sensors utilize the I2C communication protocol, which allows multiple slave devices to connect to the same serial clock (SCL) and serial data (SDA) pins as long as each device maintains a unique hardware address.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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