send an email when the temperature reaches 32°C or above using a DHT sensor with Raspberry Pi:

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🔥 Sending Email Alert When Temperature Exceeds 32°C Using Raspberry Pi and DHT11/DHT22

Monitoring temperature is one of the most common use cases for Raspberry Pi-based IoT systems. In this tutorial, we will show you how to use a DHT11 or DHT22 sensor with Raspberry Pi to read temperature and send an email alert when it reaches 32°C or above.

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🧰 Requirements

• Raspberry Pi (any model with GPIO, e.g., Pi 3/4/Zero W)

• DHT11 or DHT22 sensor

• Jumper wires

• Python 3

• Internet connection (for sending emails)

• Gmail account (or any SMTP-compatible email)

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🔌 Wiring the DHT Sensor

⚠️ Use a 10kΩ resistor between VCC and DATA for DHT22 (optional but recommended for stable readings).

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🐍 Installing Dependencies

1. Update packages:

    sudo apt update
    sudo apt install python3-pip
   

2. Install Adafruit DHT library:

    pip3 install Adafruit_DHT
   

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📧 Enable Gmail for App Access

If using Gmail:

1. Go to Google Account Security

2. Turn "2-Step Verification" ON.

3. Generate an App Password.

4. Save that password — it replaces your usual password in code.

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💻 Python Script to Monitor Temperature and Send Email

import Adafruit_DHT
import smtplib
from email.mime.text import MIMEText
import time

# Constants
DHT_SENSOR = Adafruit_DHT.DHT11  # Use DHT22 if needed
DHT_PIN = 4                      # GPIO4
ALERT_TEMP = 32.0                # Temperature threshold

# Email config
SMTP_SERVER = "smtp.gmail.com"
SMTP_PORT = 587
EMAIL_FROM = "your_email@gmail.com"
EMAIL_TO = "receiver_email@gmail.com"
EMAIL_SUBJECT = "Temperature Alert!"
EMAIL_PASSWORD = "your_app_password"  # Use App Password for Gmail

def send_email(temp):
    body = f"Warning! The temperature has reached {temp:.1f}°C."
    msg = MIMEText(body)
    msg["Subject"] = EMAIL_SUBJECT
    msg["From"] = EMAIL_FROM
    msg["To"] = EMAIL_TO

    try:
        with smtplib.SMTP(SMTP_SERVER, SMTP_PORT) as server:
            server.starttls()
            server.login(EMAIL_FROM, EMAIL_PASSWORD)
            server.sendmail(EMAIL_FROM, EMAIL_TO, msg.as_string())
        print("Email sent!")
    except Exception as e:
        print("Failed to send email:", e)

# Main loop
if __name__ == "__main__":
    alert_sent = False
    try:
        while True:
            humidity, temperature = Adafruit_DHT.read_retry(DHT_SENSOR, DHT_PIN)
            if temperature:
                print(f"Temp={temperature:.1f}°C Humidity={humidity:.1f}%")
                if temperature >= ALERT_TEMP and not alert_sent:
                    send_email(temperature)
                    alert_sent = True
                elif temperature < ALERT_TEMP:
                    alert_sent = False
            else:
                print("Sensor failure. Check wiring.")
            time.sleep(10)
    except KeyboardInterrupt:
        print("Stopped.")

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🧪 How It Works

• The script checks temperature every 10 seconds.

• If the temperature reaches 32°C or above, an email is sent.

• A flag (alert_sent) ensures only one email is sent until the temperature drops below 32 again.

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