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Pulse Monitor

A real-time heart rate monitor using an analog pulse sensor and ESP32, displaying live BPM and waveform on an SSD1306 OLED display — built with MicroPython.

Hardware Required

Component Quantity
ESP32 1
Analog Pulse Sensor Module 1
SSD1306 OLED Display (0.96", I2C) 1
Jumper Wires Few
Breadboard 1

Wiring

circuit_image

Pulse Sensor → ESP32

Pulse Sensor ESP32
VCC (Red) 3.3V
GND (Black) GND
Signal GPIO34

OLED → ESP32

OLED ESP32
VCC 3.3V
GND GND
SDA GPIO21
SCL GPIO22

Getting Started

1. Flash MicroPython

Flash MicroPython firmware on your ESP32 from micropython.org.

2. Install ssd1306 library

In Thonny, install ssd1306 via Tools → Manage Packages, or copy ssd1306.py to your ESP32.

3. Upload & Run

Upload main.py to ESP32 and run it. Place finger on the pulse sensor and watch the OLED come alive!

How It Works

  • ADC Reading — Pulse sensor output is read via GPIO34 (ADC). ATTN_11DB enables full 0–3.3V range.
  • Peak Detection — When ADC value crosses THRESHOLD (2500) and minimum interval has passed, a heartbeat is detected.
  • BPM Calculation — Average time between last 10 peaks is used: BPM = 60000 / avg_interval_ms
  • Waveform Display — Last 80 ADC samples are stored in a buffer and drawn as a scrolling line graph on the top half of OLED.
  • Heart Symbol — Drawn pixel-by-pixel using oled.pixel() calls in a 7×5 grid pattern.

OLED Layout

┌────────────────────────┐
│      live waveform     │  ← top half (y: 0–37)
│────────────────────────│  ← divider
│  ❤ : 72 BPM           │  ← bottom half (y: 44)
└────────────────────────┘

Author

Kritish Mohapatra
B.Tech Electrical Engineering (3rd Year)
IoT | Embedded Systems | MicroPython | ESP32

⭐ Support

If you like this project, give it a ⭐ on GitHub and feel free to fork it!

Happy hacking 🚀