Portable Air Quality Meter

Project overview

DIY Portable Air Quality Index (AQI) Monitor Overview This project is a compact, handheld Air Quality Index (AQI) monitoring device designed to measure ambient air pollution in real time. Built using an Arduino Pro Mini, an MQ-135 air quality sensor, a 0.96-inch I2C OLED display, and powered by a LiPo battery, this device provides a portable solution for detecting hazardous gases and general air quality levels indoors or outdoors. Core Components & Architecture Microcontroller: Arduino Pro Mini Serves as the brain of the project, handling analog signals from the sensor, executing threshold logic, and driving the OLED interface over I2C.Selected for its ultra-compact form factor, low power consumption, and minimal footprint on the perfboard/PCB .Gas Sensor: MQ-135Detects a wide spectrum of air pollutants including Ammonia , Nitrogen Oxides, Alcohol, Benzene, Smoke, and Carbon Dioxide. Uses an internal heating element and a tin dioxide sensitive layer whose resistance changes proportionally with gas concentration. Communicates with the Arduino via an analog output pin. Display Module: 0.96-inch OLED (SSD1306)Monochrome I2C display powered by 4 pins (GND, VDD, SCK, SDA). Displays the real-time raw/calibrated sensor value and maps it to a human-readable qualitative status (e.g., "Poor Air").Power Supply: LiPo Battery Enables untethered, mobile operation. Can be paired with a small TP4056 charging module and step-up boost converter to regulate voltage for the Arduino and sensor. The Arduino’s internal 10-bit ADC converts this signal into a raw numerical value ranging from 0 to 1023.Data Processing: The code averages readings to filter out electrical noise and heater fluctuations, then compares the value against programmed safety thresholds .Visual Feedback: Header: Displays -- AIR MONITOR --Numeric Output: Shows the current gas concentration reading. Air Quality Status: Categorizes air quality based on defined thresholds: Clean Air / Good: Low concentration values Moderate: Medium gas levels Poor Air: High concentration values (as shown on screen)Key Applications & Advantage Portability: Battery operation and a minimal board layout allow for real-time monitoring on the move. Indoor Air Safety: Ideal for checking ventilation levels in office spaces, workshops, kitchen areas, or residential rooms. Cost-Effective: Assembled entirely with accessible, budget-friendly off-the-shelf electronics components.