# Air Quality Monitor
**Air Quality Monitor** is a lightweight web interface that displays real-time data from two environmental sensors: **HTU21D** and **BMP180**. The system uses **NGINX** to serve an HTML page that reads live data from JSON files.
## Project Description
This project was designed to visualize environmental parameters in a simple, fast, and efficient way using an embedded graphical interface. The data is obtained from the following sensors:
- **HTU21D**: Temperature and relative humidity.
- **BMP180**: Atmospheric pressure and temperature.
The data is stored in two JSON files, updated by the embedded system and displayed through an HTML/JavaScript-based frontend.
---
## Project Structure
air-quality-monitor/
│
├── BMP180.json # Pressure and temperature data from BMP180
├── HTU21D.json # Temperature and humidity data from HTU21D
├── index.html # Main web interface
├── index.js # JavaScript logic to fetch and display JSON data
├── style.css # Custom CSS styles
> The `.json` files are automatically updated by C programs that communicate with the sensors via I2C.
---
## 🚀 Installation & Deployment with NGINX
### Requirements
- Linux server with `nginx` installed.
- Root access or permission to modify NGINX configuration.
### Steps
1. Install NGINX (if not already installed):
```bash
sudo apt update
sudo apt install nginx
```
2. Copy the project files to NGINX’s public directory (e.g., /var/www/html):
``` bash
```
3. Redirect the configuration file to our repository folder:
```bash
sudo vi /etc/nginx/sites-available/default
```
4. Replace the line:
```bash
root /var/www/html;
```
with:
```bash
root /home/debian/path/to/your/repository;
```
5. Apply chages with:
```bash
sudo systemctl restart nginx
```
## User interface
This is a simple web page that displays real-time sensor data from two devices:
• BMP180: Shows temperature and pressure.
• HTU21D: Shows humidity and temperature.
It’s styled with a separate CSS file (style.css) and fetches live data using JavaScript (index.js), which likely reads values from two JSON files (BMP180.json and HTU21D.json).
### HTML
#### Complete code
```html
Sensor Dashboard
Sensor Dashboard
BMP180
Temperature: -- °CPressure: -- hPa
HTU21D
Humidity: -- %Temperature: -- °C
```
#### Explanation
```html
```
• Declares this document as HTML5.
• lang="en" sets the document language to English, which is useful for accessibility and SEO.
##### HEAD
```html
Sensor Dashboard
```
• charset="UTF-8" ensures proper text encoding.
• viewport makes the layout responsive on mobile devices.
• title is what appears in the browser tab.
• link imports the external CSS file (style.css) for styling.
##### BODY
```html
...
```
• The background div might be used for a visual effect like a background image or color gradient (defined in your CSS).
• container holds the main content (dashboard).
• index.js is loaded at the end to ensure the DOM is ready before scripts run.
##### Dashboard Title
```html
Sensor Dashboard
```
• This is the main heading of your web page.
##### Sensor Card: BMP180
```hmtl
BMP180
Temperature: -- °CPressure: -- hPa
```
• This block represents the BMP180 sensor.
• The icon (from flaticon.com) visually represents pressure/temperature.
• The id attributes (temperature, pressure) are hooks used by JavaScript to insert real values from BMP180.json.
##### Sensor Card: HTU21D
```html
HTU21D
Humidity: -- %Temperature: -- °C
```
• This block represents the HTU21D sensor.
• The image is a humidity icon.
• The id attributes (humidity, tempHTU) are also updated by JavaScript using HTU21D.json.
##### JavaScript Integration
```hmtl
```
• This line loads your script, which is responsible for:
• Fetching the JSON files.
• Parsing their content.
• Replacing the placeholder values (-- °C, -- hPa, etc.) with live sensor data.
### Index.js
The script fetches data from two local JSON files:
• BMP180.json — contains temperature and pressure.
• HTU21D.json — contains temperature and humidity.
Then it updates the HTML every 3 seconds so the page always shows live sensor values.
#### Full code
```js
function updateBMP180() {
fetch('BMP180.json')
.then(res => res.json())
.then(data => {
document.getElementById('temperature').textContent = `Temperature: ${data.temperature.toFixed(2)} °C`;
document.getElementById('pressure').textContent = `Pressure: ${data.pressure.toFixed(2)} hPa`;
})
.catch(err => console.error("Error BMP180:", err));
}
function updateHTU21D() {
fetch('HTU21D.json')
.then(res => res.json())
.then(data => {
document.getElementById('humidity').textContent = `Humidity: ${data.humidity.toFixed(1)} %`;
document.getElementById('tempHTU').textContent = `Temperature: ${data.temperature.toFixed(1)} °C`;
})
.catch(err => console.error("Error HTU21D:", err));
}
setInterval(() => {
updateBMP180();
updateHTU21D();
}, 3000);
// Carga inicial
updateBMP180();
updateHTU21D();
```
### Code explanation
#### Function: updateBMP180
```js
function updateBMP180() {
fetch('BMP180.json')
.then(res => res.json())
.then(data => {
document.getElementById('temperature').textContent = `Temperature: ${data.temperature.toFixed(2)} °C`;
document.getElementById('pressure').textContent = `Pressure: ${data.pressure.toFixed(2)} hPa`;
})
.catch(err => console.error("Error BMP180:", err));
}
```
- This defines a new function named updateBMP180. You’ll call this function when you want to update the BMP180 sensor data on the page.
- fetch('BMP180.json'): Loads the JSON file from the same directory.
- .then(res =\>json()): Parses the response as JSON
- .then(data +\> {}): Accesses the data inside the file.
- document.getElementById(...) updates the corresponding elements in your HTML.
#### Function: updateHTU21D
```js
function updateHTU21D() {
fetch('HTU21D.json')
.then(res => res.json())
.then(data => {
document.getElementById('humidity').textContent = `Humidity: ${data.humidity.toFixed(1)} %`;
document.getElementById('tempHTU').textContent = `Temperature: ${data.temperature.toFixed(1)} °C`;
})
.catch(err => console.error("Error HTU21D:", err));
}
```
Works the same way as updateBMP180(), but:
- Fetches from HTU21D.json.
- Displays humidity and temperature.
- Uses .toFixed(1) for 1 decimal place (common for humidity values).
#### Auto-update every 3 seconds
```js
setInterval(() => {
updateBMP180();
updateHTU21D();
}, 3000);
```
- Calls both update functions every 3,000 milliseconds (3 seconds).
- Keeps the UI in sync with new sensor readings, assuming the .json files are being updated continuously.
#### Initial load
```js
updateBMP180();
updateHTU21D();
```
- Ensures the data is shown immediately on page load, before the 3-second interval kicks in.
### CSS
#### Full code
```css
* {
margin: 0;
padding: 0;
box-sizing: border-box;
font-family: "Segoe UI", sans-serif;
}
body, html {
height: 100%;
background-color: #0d1117;
color: #ffffff;
position: relative;
overflow: hidden;
}
.background {
background-image: url('https://wallpapers.com/images/hd/blue-circuit-board-traces-zn0xezd4t8axj9r6.webp');
background-size: cover;
background-position: center;
opacity: 0.1;
filter: blur(3px);
position: absolute;
top: 0; left: 0;
width: 100%;
height: 100%;
z-index: -1;
}
.container {
max-width: 800px;
margin: 40px auto;
background-color: #161b22;
padding: 30px;
border-radius: 20px;
box-shadow: 0 0 30px rgba(0, 255, 255, 0.2);
animation: fadeIn 1s ease-in;
}
h1 {
text-align: center;
margin-bottom: 30px;
font-size: 2.5rem;
color: #58a6ff;
}
.sensor-card {
background-color: #1f2937;
padding: 20px;
border-radius: 15px;
margin-bottom: 20px;
box-shadow: 0 0 20px rgba(100, 255, 255, 0.1);
animation: slideIn 1s ease;
display: flex;
flex-direction: column;
align-items: center;
text-align: center;
}
.sensor-card img {
width: 64px;
height: 64px;
margin-bottom: 10px;
}
.sensor-card h2 {
margin-bottom: 10px;
color: #90cdf4;
}
.data span {
display: block;
margin: 5px 0;
font-size: 1.2rem;
color: #ffffff;
}
@keyframes fadeIn {
from { opacity: 0; transform: translateY(-20px); }
to { opacity: 1; transform: translateY(0); }
}
@keyframes slideIn {
from { opacity: 0; transform: scale(0.9); }
to { opacity: 1; transform: scale(1); }
}
```
#### Explaining
Global Styling
- *: Resets default browser spacing (margin, padding) and sets a consistent font and box model across the entire page.
- body, html:
- Sets full height layout.
- Applies a dark background (#0d1117) with white text.
- Hides overflow and enables positioning for internal layers.
⸻
Background Layer
- .background:
- Adds a faint, blurred circuit board image as the background.
- Uses opacity: 0.1 and filter: blur(3px) to give it a soft tech feel.
- Positioned absolutely behind everything (z-index: -1).
⸻
Main Container
- .container:
- A centered, card-like section with:
- A dark background (#161b22)
- Rounded corners and soft glowing shadow.
- Padding and a fade-in animation on load.
⸻
Title
- h1:
- Large, centered header in light blue (#58a6ff).
- Styled to stand out at the top of the dashboard.
⸻
Sensor Cards
- .sensor-card:
- Styled boxes for each sensor.
- Darker background (#1f2937) with a soft shadow.
- Rounded corners, padding, and a slide-in animation when they load.
- Contents are centered vertically and horizontally.
- .sensor-card img:
- Sensor icons sized to 64×64 pixels with margin for spacing.
- .sensor-card h2:
- Sub-headers for each sensor card in a soft blue (#90cdf4).
⸻
Data Text
- .data span:
- Each line of sensor data (e.g., temperature, humidity).
- Displayed as blocks with spacing and larger font for visibility.
⸻
Animations
- @keyframes fadeIn:
- Smooth slide-down + fade-in for the container.
- @keyframes slideIn:
- Subtle zoom-in effect for each sensor card.
## Sensor library
### HTU21D library
The library contains 3 files, HTU21D.c, htu21d.h and main.c
#### htu21d.h
```h
#ifndef HTU21D_H
#define HTU21D_H
// HTU21D i2c address
#define HTU21D_ADDR 0x40
//commands for readings
#define HTU21D_TEMP 0xE3
#define HTU21D_HUM 0xE5
#define HTU21D_RESET 0xFE
//funtion declarations
//Temp:
int getTemp(int fd, double *temp);
//HUM
int getHum(int fd, double *hum);
//RESET
int getReset(int fd);
#endif
```
- HTU21D_ADDR: The I2C address of the sensor (0x40).
- HTU21D_TEMP: Command to read temperature (0xE3).
- HTU21D_HUM: Command to read humidity (0xE5).
- HTU21D_RESET: Command to reset the sensor (0xFE).
- Declares three functions:
1. getTemp() – for reading temperature,
2. getHum() – for reading humidity,
3. getReset() – for resetting the sensor.
