Home Air Monitoring System

Home Air Monitoring System (HAMS) is my personal hardware & embedded software development project designed to monitor indoor and outdoor air quality in my home.

Overview

The system consists of a central hub and six wireless sensor nodes to measure:

• Temperature
• Relative Humidity
• Atmospheric Pressure
• Particulate Matter
• Volatile Organic Compounds (VOCs)
• NOₓ
• CO₂

System Components

• Central Hub

  • ESP32-based; mains-powered.
  • Connects to the internet for weather updates and time synchronization via SNTP.
  • Displays real-time measurements on a 7.5" 800x480 e-ink screen with a 1 minute refresh rate.
  • Contains sensors for all previously listed quantities.
  • Screen-sized 3D-printed enclosure (estimated 175 mm x 92.65 mm x 120 mm).

• Sensor Nodes

  • STM32-based and battery-powered, optimized for low power consumption and long battery life.
  • Equipped with temperature and humidity sensors only, with optional hardware support for one more sensor.
  • Transmit data to the hub every minute using nRF24 radio modules.
  • Minimalistic and visually non-intrusive 3D-printed case with a small form factor (estimated 81 mm x 58 mm x 28 mm).

Sensors

• SHT40
  • Temperature and humidity sensor from Sensirion.
  • Used in the central hub and sensor nodes.
  • Temperature accuracy: ±0.2 °C
  • Humidity accuracy: ±1.8 %RH
• SCD41
  • CO2 sensor from Sensirion.
  • Used in the central hub.
  • CO2 accuracy: ±50 ppm ± 5.0 %m.v. (depending on range)
• SGP41
  • VOC and NOx gas index sensor from Sensirion.
  • Used in the central hub.
• SPS30
  • Particulate matter sensor from Sensirion.
  • Used in the central hub.
  • Accuracy: ±10 %
• BME280
  • Temperature, relative humidity and atmospheric pressure sensor from Adafruit.
  • Used in the central hub (for atmospheric pressure only).
  • Atmospheric pressure accuracy: ±1 hPa

Documentation

• Hub
• Nodes
• SHT4x calibration

Repository Structure

├── docs                         # Documentation for project setup, usage, etc.
├── utilities                    # Various auxiliary scripts, tools etc.
│   ├── sht_sensor_burn_in       # PlatformIO Arduino project for SHT40 sensor burn-in
│   └── sht_sensor_calibration   # PlatformIO Arduino project for SHT40 sensor calibration
├── hub
│   ├── hardware                 # PCB design and schematic for hub
│   ├── firmware                 # Firmware for the ESP32-based central hub
│   └── 3D_models                # 3D models for the hub's enclosure
├── node
│   ├── firmware                 # Firmware for the STM32-based sensor nodes
│   ├── hardware                 # PCB designs and schematics for nodes
│   └── 3D_models                # 3D models for the nodes' enclosures
├── README.md                    # Project overview (you are reading this now!)
└── TODO.md                      # Project task list