Raspberry Pi-Based SMS Alert System Using Circuit Digest Cloud API

A modern, Wi-Fi-based SMS alert system that monitors temperature using a DHT11 sensor and sends real-time alerts to your phone - no GSM modules or SIM cards required.

🚀 Project Overview

This project creates a temperature monitoring system using a Raspberry Pi that sends SMS alerts when temperature thresholds are exceeded. The system uses the Circuit Digest Cloud API to send messages over Wi-Fi, making it simple and cost-effective compared to traditional GSM-based solutions.

Key Features:

• Real-time temperature monitoring with DHT11 sensor
• Wi-Fi-based SMS alerts (no SIM card needed)
• Visual feedback with LED indicators
• Configurable temperature thresholds
• Anti-spam cooldown mechanism
• Easy setup and deployment

🛠️ Components Required

Component	Quantity
Raspberry Pi (any model 3,4,5)	1
DHT11 Temperature Sensor	1
220Ω Resistors (for LEDs)	1
LEDs (Red, Green)	2
Breadboard & Jumper Wires	As needed

📋 Prerequisites

Raspberry Pi Setup

1. Install latest Raspberry Pi OS using the official Raspberry Pi Imager
2. Connect to internet (Wi-Fi or Ethernet)
3. Update system packages:

   sudo apt update && sudo apt upgrade -y

Python Library Installation

Due to PEP 668 restrictions on newer Raspberry Pi OS versions, you have two installation options:

Option 1: Override system packages (quick but not recommended)

sudo pip3 install --break-system-packages Adafruit_DHT requests

Option 2: Virtual environment (recommended)

sudo apt install python3-venv -y
python3 -m venv myenv
source myenv/bin/activate
pip install Adafruit_DHT requests

🔧 Circuit Digest Cloud Setup

Account Registration

1. Visit Circuit Digest Cloud
2. Click "Login" → "Register Now" for new users
3. Complete registration with email, username, and password
4. Log in with your credentials

API Key Generation

1. Navigate to "My Account" in the top-right corner
2. Complete the captcha verification
3. Click "Generate API Key"
4. Copy your API key for use in the code

Mobile Number Verification

Important: You must verify your mobile number using OTP authentication before receiving SMS alerts. This prevents spam and ensures authorized usage.

API Usage Limits

• SMS API Keys: 100 requests per key
• Generate new keys when quota is exhausted
• Fair use policy applies

🔌 Hardware Wiring

Pin Connections

• DHT11 Sensor: GPIO4 (Pin 7)
• Green LED: GPIO23 (Pin 16)
• Red LED: GPIO24 (Pin 18)
• Ground: Connect all ground pins to common ground rail

📝 SMS Templates

The system uses template ID 102 for temperature alerts:

Template 102 - Temperature Alert:

The temperature in {#var1#} has reached {#var2#}°C. Please take necessary action.
-- 
Powered by CircuitDigest for the Engineers and Makers of India. Visit www.circuitdigest.com.

Variables:

• var1: Location and timestamp (e.g., "Home at 02:45 PM")
• var2: Temperature value (e.g., "34")

⚙️ Configuration

Update the following variables in the code:

API_KEY = 'your_api_key_here'           # Your Circuit Digest API Key
TEMPLATE_ID = '102'                     # Temperature alert template
MOBILE_NUMBER = '91xxxxxxxxxx'          # Target mobile number with country code
LOCATION = 'Home'                       # Location label for SMS
TEMP_THRESHOLD = 33                     # °C: Trigger SMS if temp exceeds this
READ_INTERVAL = 10                      # Seconds between sensor reads
COOLDOWN_TIME = 60                      # Seconds to wait after sending SMS

🚀 Running the System

1. Navigate to project directory:

   cd /path/to/your/project

2. Activate virtual environment (if using):

   source myenv/bin/activate

3. Run the monitoring script:

   python3 sms_alert_system.py

4. Monitor output:

   Monitoring temperature... (Press Ctrl+C to stop)
   Temperature: 25C | Humidity: 45%
   Temperature: 35C | Humidity: 50%
   [OK] SMS sent: Home at 02:45 PM, Temp = 35C
   

🔍 System Behavior

Normal Operation

• Continuously monitors temperature every 10 seconds
• Displays temperature and humidity readings
• Green LED blinks when SMS is sent successfully
• Red LED blinks when SMS sending fails

Alert Triggering

• SMS sent when temperature exceeds threshold (default: 33°C)
• 60-second cooldown prevents spam alerts
• Visual feedback via LED indicators

Error Handling

• Sensor read failures are logged and retried
• Network connection errors trigger red LED
• Graceful shutdown with Ctrl+C

🛠️ Troubleshooting

Problem	Solution
SMS not received	Ensure mobile number is verified in Circuit Digest account
Library install fails	Use --break-system-packages or create virtual environment
Network timeout	Check internet connection with ping www.google.com
GPIO pins don't respond	Verify pin numbers (BCM vs physical numbering)
Sensor read errors	Normal for DHT11 - system retries automatically

📊 Testing

1. Heat the sensor with warm air or hair dryer
2. Watch console output for temperature readings
3. Verify SMS delivery when threshold is exceeded
4. Check LED feedback for success/failure indication

🤝 Contributing

We welcome contributions and would love to see how you use this system! Feel free to:

• Submit bug reports and feature requests
• Share your project implementations
• Suggest new SMS templates
• Improve documentation

Happy Building! 🎉