This project involves the development of a smart environmental monitoring and control system that integrates various sensors and actuators to ensure optimal environmental conditions. The system utilizes a DHT11 sensor for temperature and humidity monitoring, an MQ2 sensor for gas detection, and an LCD for real-time data display. It also includes a relay-controlled fan for ventilation and a red LED for visual alerts. The system is designed to operate both automatically and manually, providing flexibility and enhanced safety.

In the current era, where safety in residential areas and industrial factories is paramount, the development of a "Smart Environmental Monitoring and Control System" is a solution that addresses both safety maintenance and the creation of suitable environmental conditions. This project integrates embedded systems with high-performance sensors to monitor for unseen dangers.

Project Overview

This project is an automated control system that operates in Real-time, relying on processing from an Arduino microcontroller to measure temperature, humidity, and gas concentration in the air. When the system detects abnormalities, such as a gas leak or excessively high temperature, it will immediately activate the fan driver unit (Fan) to ventilate the area. It also displays the status via an LCD screen and a visual alert to promptly inform users of the situation.

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Components & Engineering

The core of the system consists of key components that work together systematically, as follows:

1. DHT11 (Temperature & Humidity Sensor)

A digital temperature and humidity sensor that uses single-bus data transmission. It internally comprises an NTC (Negative Temperature Coefficient) thermistor for temperature measurement and a capacitive humidity sensing element for humidity. This provides sufficient accuracy for indoor monitoring.

2. MQ2 (Gas & Smoke Sensor)

A Metal Oxide Semiconductor (MOS) gas sensor sensitive to LPG, propane, hydrogen, and smoke. It operates on the principle of changing resistance in its semiconductor material (SnO2) when exposed to reactive gases. The system uses the resulting analog voltage value to calculate the gas density in the air.

3. Relay Module & Ventilation Fan

Since fans typically require higher current and voltage than what Arduino can supply directly, we use a Relay as an electronic switch to isolate the control section (Low Voltage) from the power section (High Voltage), enabling safe control of the ventilation fan.

4. LCD Display & Visual LED

• LCD (Liquid Crystal Display): Acts as a User Interface, displaying temperature, humidity, and gas levels in Real-time.
• Red LED: Serves as a critical alert indicator to be noticeable from a distance.

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System Logic & Algorithm

The program is designed to operate as a State Machine and uses Threshold Monitoring, with the following operational steps:

1. Data Acquisition: The system reads values from the DHT11 and MQ2 sensors at defined intervals (Sampling Rate).
2. Processing & Comparison:
   • Compares the read gas value with the Threshold (critical point) set in the Code.
   • Compares the temperature value with the defined range to assess the risk of heat accumulation.
3. Action Logic:
   • Automatic Mode: If the gas value exceeds the standard or the temperature is too high, the system sends a High signal to the Relay to turn on the fan, and commands the red LED to blink or stay solid.
   • Manual Override: Users can manually turn the ventilation system on or off via a switch or a designed interface (if additional connections are made).
4. Feedback Loop: Displays the current results on the LCD screen, allowing users to know the various parameters at all times.

// Basic Control Logic Example (Conceptual Code)
if (gasValue > gasThreshold || tempValue > tempThreshold) {
    digitalWrite(RELAY_PIN, HIGH); // Turn on fan
    digitalWrite(LED_PIN, HIGH);   // Turn on warning light
} else {
    digitalWrite(RELAY_PIN, LOW);  // Turn off fan
    digitalWrite(LED_PIN, LOW);    // Turn off warning light
}

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Key Features

• Dual-Safety System: Protects against both temperature issues (preventing overheating) and gas leak problems within a single system.
• Real-time Visualization: Environmental values are known instantly via the screen, no guesswork needed.
• Autonomous Response: The system responds to dangers autonomously without human intervention, reducing the risk of accidents.
• Expandability: Can be further developed to connect with IoT systems (e.g., ESP32 or Blynk) to send notifications to smartphones in the future.

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Downloads & Resources

You can download the full circuit diagram (Schematic) and source code from the links below:

[Download Source Code]
[Download Circuit Diagram]

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We hope this project serves as a useful guideline for engineers and those interested in building Smart Home or Industrial Monitoring systems!