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277 lines
4.9 KiB
Markdown
277 lines
4.9 KiB
Markdown
# Raspberry Pi 4 Temperature & Humidity Monitoring System (HTU21D)
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---
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## Project Overview
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This project implements a real-time temperature and humidity monitoring system using a **Raspberry Pi 4** and an **HTU21D sensor**. The system reads environmental data via I2C, processes it using a C program, and displays the results on a web dashboard using Nginx.
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---
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## System Architecture
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The system is structured as a simple data pipeline that connects the sensor, processing logic, and web interface. Data flows continuously from the physical environment to the user in a clear and modular way.
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---
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### 🔹 Hardware and Communication Layer
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The HTU21D sensor measures temperature and humidity and communicates with the Raspberry Pi using the I2C protocol. This allows the Raspberry Pi to request and receive raw data from the sensor.
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---
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### 🔹 Data Processing Layer
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A C program interacts with the I2C interface to read the sensor data. It converts the raw binary values into human-readable units such as degrees Celsius and percentage humidity, and formats the result as JSON.
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---
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### 🔹 Data Storage Layer
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The JSON file stores the latest sensor readings. It acts as an intermediate layer, separating the data acquisition process from the web interface.
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---
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### 🔹 Web Server Layer
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Nginx serves the JSON file and the web page over HTTP. It allows other devices on the network to access the system through a browser.
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---
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### 🔹 Presentation Layer
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The web page uses JavaScript to periodically request the JSON file and update the displayed values dynamically, enabling near real-time visualization.
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---
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### Overall Flow
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Data is captured by the sensor, processed by the C program, stored as JSON, served by Nginx, and displayed in the browser. This structure keeps the system simple, modular, and easy to maintain.
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---
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## Materials
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### Hardware
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* Raspberry Pi 4
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* HTU21D sensor
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* Jumper wires (female-to-female)
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* MicroSD card with Raspberry Pi OS
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* Power supply
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### Software
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* Raspberry Pi OS / Debian
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* GCC compiler
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* i2c-tools
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* libi2c-dev
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* Nginx
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* Git
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---
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## Hardware Connections
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### Pin Reference Images
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---
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### Wiring Table
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| HTU21D | Raspberry Pi 4 |
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| ------ | -------------- |
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| VCC | 3.3V |
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| GND | GND |
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| SDA | GPIO2 (SDA) |
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| SCL | GPIO3 (SCL) |
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---
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## Deployment Guide (From Scratch)
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### 1. Install Dependencies
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```bash
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sudo apt update
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# Updates package list
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sudo apt install gcc i2c-tools libi2c-dev nginx git
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# Installs compiler, I2C tools, web server, and Git
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```
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---
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### 2. Clone the Repository
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```bash
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git clone https://gitea.itmorelia.com/Verano-Delfin-2026/Temperature-Humidity-Sensor.git
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# Downloads the project from the server
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cd Temperature-Humidity-Sensor
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# Enters the project folder
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```
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---
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### 3. Enable I2C
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```bash
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sudo raspi-config
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# Opens Raspberry Pi configuration menu
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```
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Go to:
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```
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Interfacing Options → I2C → Enable
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```
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```bash
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sudo reboot
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# Restarts system to apply changes
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```
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---
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### 4. Verify Sensor
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```bash
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i2cdetect -y 1
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# Scans I2C bus for connected devices
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```
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Expected:
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```
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0x40
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```
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---
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### 5. Compile the Sensor Program
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```bash
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cd sensors/HTU21D
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# Move to sensor source code
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gcc main.c htu21d.c -o HTU21D -li2c
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# Compiles the program and links I2C library
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```
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---
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### 6. Deploy Web Files
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```bash
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sudo cp -r ~/basic-ui-dashboard/* /var/www/html/
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# Copies project files to Nginx directory
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```
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```bash
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sudo mkdir -p /var/www/html/data
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# Creates folder for JSON output
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```
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---
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### 7. Set Permissions
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```bash
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sudo chmod +x /var/www/html/sensors/HTU21D/HTU21D
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# Allows execution of sensor program
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sudo chown -R www-data:www-data /var/www/html
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# Gives Nginx access to files
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```
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---
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### ▶8. Run Sensor Loop
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```bash
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cd /var/www/html
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# Go to web directory
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while true; do ./sensors/HTU21D/HTU21D > data/HTU21D.json; sleep 5; done
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# Continuously updates JSON every 5 seconds
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```
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---
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### 9. Start Nginx
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```bash
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sudo systemctl start nginx
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# Starts web server
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sudo systemctl enable nginx
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# Enables auto-start on boot
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sudo systemctl status nginx
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# Verifies server is running
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```
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---
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### 10. Get Raspberry Pi IP
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```bash
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hostname -I
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# Displays local IP address
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```
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Example:
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```
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192.168.1.100
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```
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---
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### 11. Access from Another Computer
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Open a browser and go to:
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```
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http://192.168.1.100
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```
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---
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### 12. Result
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---
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## Real-Time Updates
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JavaScript fetch:
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```javascript
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fetch('./data/HTU21D.json?nocache=' + Date.now())
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```
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**What it does:**
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* Prevents browser cache
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* Forces fresh data request
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## Conclusion
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This project integrates:
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* Embedded systems (sensor + Raspberry Pi)
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* C programming
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* Linux system configuration
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* Web development (Nginx + JS)
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It demonstrates a complete pipeline from hardware acquisition to real-time web visualization.
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---
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