🌤️ IoT Weather Station — Arduino + MQTT

An Arduino-based IoT weather station that measures wind speed and sound intensity, transmitting real-time data to a cloud database via MQTT over Ethernet.

Built as part of the Embedded Systems Project Work course at Tampere University of Applied Sciences (TAMK), Spring 2025.

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📋 Table of Contents

• Overview
• System Architecture
• Hardware Components
• Software Design
• Test Cases
• Getting Started
• Project Structure
• Team

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Overview

The weather station collects two environmental parameters:

Parameter	Sensor	Interface
Sound Intensity	DFRobot Gravity Analog Sound Sensor (DFR0034)	Analog (A0)
Wind Speed	Anemometer signal box (lab)	Digital interrupt (Pin 2)

Data is processed by an Arduino Nano/Mega and published to an MQTT broker every 5 seconds. The broker forwards data to a cloud SQL database, retrievable via a REST API.

Wind speed is calculated using the anemometer transfer function:

U (m/s) = -0.24 + F (Hz) × 0.699

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System Architecture

┌─────────────────────────────────────────────────────┐
│                   IoT Layer Stack                   │
│                                                     │
│  [Sound Sensor]  [Wind Sensor/Anemometer]           │
│         │                  │                        │
│         └──────┬───────────┘                        │
│                ▼                                    │
│         [Arduino Nano]   ← Device Layer             │
│         (C++ Firmware)                              │
│                │                                    │
│                ▼                                    │
│      [Ethernet Shield W5100]  ← Gateway Layer       │
│                │                                    │
│                ▼                                    │
│      [MQTT Broker :1883]  ← Cloud Layer             │
│                │                                    │
│                ▼                                    │
│      [SQL Database + REST API]                      │
└─────────────────────────────────────────────────────┘

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Hardware Components

Component	Specification	Function
Microcontroller	Arduino Mega / Nano	Central processing unit
Sound Sensor	DFRobot DFR0034	Analog sound intensity measurement
Wind Sensor	Signal box (anemometer output)	Frequency-based wind speed input
LCD Display	20×4 Character LCD	Real-time local data display
Ethernet Module	W5100-based shield	TCP/IP network connectivity
Push Button	With 10 kΩ pull-down resistor	Transmission mode selector

Pin Mapping:

Pin	Connected To
A0	Sound sensor (analog)
D2	Wind sensor (external interrupt, falling edge)
D3–D8	LCD display (parallel interface)
D9	Push button (mode select)

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Software Design

Libraries Used

Library	Purpose
LiquidCrystal.h	LCD display control
TimerOne.h	Hardware timer interrupt (1 s tick)
Ethernet.h	W5100 Ethernet shield / DHCP
PubSubClient.h	MQTT client (publish/subscribe)

Key Functions

Function	Description
pulseISR()	Counts falling edges from wind sensor on Pin 2
timerISR()	Fires every 1 s; calculates frequency over a 10 s gate
readAverageAnalog()	Averages N ADC samples with configurable delay
handleButton()	Cycles transmission mode with 50 ms debounce
publishData()	Builds JSON payload and publishes to MQTT topic
connectMQTT()	Handles MQTT broker connection and reconnection
updateDisplay()	Refreshes 20×4 LCD with current sensor values

Transmission Modes

Controlled by a push button — cycles through three modes:

[Default: ANALOG] → [DIGITAL] → [BOTH] → [ANALOG] → ...

Mode	Data Sent
ANALOG	Sound intensity only
DIGITAL	Wind speed only
BOTH	Sound intensity + Wind speed

MQTT Message Format

IOTJS={"S_name1":"EMB_sound","S_value1":245,"S_name2":"EMB_windSpeed","S_value2":312}

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Test Cases

Three formal test cases were executed to verify system correctness.

Test Case 1 — Sensor Data Averaging

Objective: Verify that readAverageAnalog() stabilises noisy ADC readings.

Environment	Raw ADC Range	Averaged Output
Quiet room	0 – 50	Stable ~5–10
Loud environment	100 – 500	Stable ~300

✅ Result: Averaging function correctly reduced noise in all conditions.

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Test Case 2 — MQTT Message Frequency & Wind Speed Accuracy

Objective: Verify frequency measurement and MQTT connectivity using a signal generator.

Signal generator settings used:

• Amplitude: 2.5 V (peak-to-peak)
• Offset: 1.25 V
• Frequency range tested: 1 Hz – 50 kHz

All wind speed outputs verified manually against the transfer function U = -0.24 + F × 0.699.

✅ Result: Frequency measurement accurate across full tested range. MQTT broker connection confirmed.

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Test Case 3 — End-to-End Data Transfer to Cloud Database

Objective: Confirm sensor data is stored in the remote SQL database and retrievable via REST API.

API endpoints tested:

GET /v1/weather/latest/EMB_windSpeed
GET /v1/weather/latest/EMB_sound

Both returned valid JSON with current readings and timestamps. Historical endpoints confirmed persistent storage.

✅ Result: Full pipeline — sensor → Arduino → MQTT → database → REST API — verified successfully.

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Getting Started

Prerequisites

• Arduino IDE (v1.8+ or v2.x)
• Required libraries (install via Arduino Library Manager):
  • TimerOne
  • PubSubClient by Nick O'Leary
  • Ethernet (built-in)
  • LiquidCrystal (built-in)

Installation

1. Clone this repository:

   git clone https://github.com/YOUR_USERNAME/iot-weather-station.git
   cd iot-weather-station

2. Open the sketch:

   Open src/weather_station/weather_station.ino in Arduino IDE
   

3. Configure your network in weather_station.ino:

   byte mqttServerIP[] = { YOUR, MQTT, BROKER, IP };
   static uint8_t mymac[6] = { 0x44, 0x76, 0x58, 0x10, 0x00, 0x62 }; // update MAC

4. Upload to your Arduino Mega/Nano with the Ethernet shield connected.

Hardware Setup

1. Connect the sound sensor to pin A0
2. Connect wind sensor signal to pin D2 (interrupt-capable)
3. Wire LCD to pins D3–D8 (RS=8, EN=7, D4=6, D5=5, D6=4, D7=3)
4. Connect push button to pin D9 with a 10 kΩ pull-down resistor to GND
5. Attach Ethernet shield on top of the Arduino

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Project Structure

iot-weather-station/
│
├── src/
│   └── weather_station/
│       └── weather_station.ino     # Main Arduino sketch
│
├── docs/
│   ├── FINAL_REPORT.pdf            # Full technical report
│   └── circuit_diagram.png         # Hardware wiring diagram (add yours)
│
├── test/
│   └── test_cases.md               # Formal test case documentation
│
├── .gitignore
├── LICENSE
└── README.md

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Team

EMB Group — TAMK Software Engineering, 2025

• Sasnu Fernando
• Piyumi Gajanayaka
• Geethika Jayasekara
• Sachini Alwis

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License

This project is licensed under the MIT License — see LICENSE for details.