🌡️ Temperature & Humidity Monitor

A simple IoT monitoring system that reads temperature and humidity from a DHT22 sensor, sends the data over WiFi to a Flask backend, and stores it in a Supabase database for tracking and alerting.

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Architecture

DHT22 Sensor
     ↓
ESP8266 (Arduino)
     ↓ HTTP POST (JSON)
Flask Server (deployed / local)
     ↓
Supabase (PostgreSQL cloud database)

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Files

File	Purpose
temp_humidity_monitor.ino	Upload to ESP8266 via Arduino IDE
server.py	Python Flask server
.env	Supabase credentials (never commit this!)
requirements.txt	Python dependencies

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Supabase Setup

1. Go to https://supabase.com and create a free account
2. Create a new project
3. Go to SQL Editor and run this to create the table:

CREATE TABLE readings (
  id          BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  temperature FLOAT        NOT NULL,
  humidity    FLOAT        NOT NULL,
  alert       BOOLEAN      NOT NULL DEFAULT FALSE,
  timestamp   TIMESTAMPTZ  NOT NULL DEFAULT NOW()
);

4. Go to Project Settings → API
5. Copy your Project URL and anon public key
6. Paste them into .env:

SUPABASE_URL=https://your-project-id.supabase.co
SUPABASE_KEY=your-anon-key-here

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Server Setup

pip install -r requirements.txt
python server.py

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Deploy Server (optional)

To make it accessible from anywhere, deploy server.py to:

• Railway — https://railway.app
• Render — https://render.com
• Fly.io — https://fly.io

Add your .env values as environment variables in the platform dashboard. Never upload your .env file to GitHub.

After deploying, update the Arduino code:

const char* SERVER_URL = "https://your-deployed-server.railway.app/log";

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Arduino Setup

Required Libraries

Install via Arduino IDE → Library Manager:

• DHT sensor library by Adafruit
• Adafruit Unified Sensor by Adafruit

ESP8266WiFi and ESP8266HTTPClient come with the ESP8266 board package.

Board Manager URL

Add under Arduino IDE → Preferences → Additional Board URLs:

http://arduino.esp8266.com/stable/package_esp8266com_index.json

Configure the Code

const char* WIFI_SSID     = "YOUR_WIFI_SSID";
const char* WIFI_PASSWORD = "YOUR_WIFI_PASSWORD";
const char* SERVER_URL    = "http://YOUR_SERVER_URL/log";

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Wiring

DHT22
  VCC  → 3.3V
  GND  → GND
  DATA → D2

Green LED (+) → 220Ω → D5
Red LED   (+) → 220Ω → D6
Buzzer    (+) → D7
All       (-) → GND

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Alert Behavior

Condition	Green LED	Red LED	Buzzer
Normal	ON	OFF	Silent
Temp > 35°C or Humidity > 80%	OFF	ON	Beep

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API Endpoints

Method	Endpoint	Description
POST	/log	Save sensor reading
GET	/readings	Last 50 readings
GET	/readings/latest	Most recent reading
GET	/readings/alerts	Alert readings only
GET	/readings/stats	Avg / Max / Min stats
DELETE	/readings/delete	Clear all records

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Troubleshooting

Problem	Solution
Supabase connection error	Check .env values are correct
ESP8266 won't connect	Double-check WiFi credentials
Server response -1	Check SERVER_URL in .ino
Sensor reads NaN	Check DHT22 wiring, use 3.3V not 5V
ModuleNotFoundError	Run pip install -r requirements.txt