IoT Environmental Monitoring System (ESP8266 + MQ-9 + DHT22 + OLED)

A fully integrated IoT-based environmental monitoring system built on ESP8266, capable of:

• Real-time Carbon Monoxide (CO) monitoring (MQ-9)
• Temperature & Humidity sensing (DHT22)
• Local OLED visualization
• Remote dashboard control via Thinger.io
• Configurable gas threshold
• Automated email alerting when safety limits are exceeded

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Project Preview

Circuit Schematic

Final Hardware Implementation

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Features

• WiFi-connected IoT device
• Cloud integration using Thinger.io
• Live dashboard monitoring
• Remote threshold configuration
• Automated email alert system
• Local OLED real-time display
• Externalized credentials (secrets.h)
• Non-blocking timing architecture
• Edge-side data processing

Data Flow

1. Sensors are sampled every 2 seconds.
2. CO concentration is calculated in ppm.
3. Values are pushed to Thinger.io.
4. If ppm exceeds threshold:
   • Email alert is triggered
   • Local OLED shows ALERT state
5. Threshold can be remotely modified from dashboard.

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Hardware Components

Component	Description
ESP8266 (NodeMCU)	WiFi microcontroller
MQ-9	Carbon Monoxide Gas Sensor
DHT22	Temperature & Humidity Sensor
SSD1306 OLED (128x64)	I2C Display
Breadboard + Jumpers	Prototyping

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Cloud Integration

Platform: Thinger.io

Dashboard Preview

The dashboard provides:

• Live CO ppm gauge
• Temperature & Humidity widgets
• Remote threshold control slider
• Real-time device status

Exposed Resources

• environment
  • temperature
  • humidity
  • ppm
• threshold
  • Read/Write numeric resource

Email Endpoint

gas_alert_email

Payload Structure

{
  "ppm": 350,
  "threshold": 200,
  "temperature": 27.5,
  "humidity": 33.8
}

Email Alert Example

When gas concentration exceeds the configured threshold, an email is automatically triggered.

The email contains:

• Current CO ppm
• Configured threshold
• Temperature
• Humidity
• Timestamp of alert

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Security Configuration

Sensitive credentials are isolated in secrets.h

Example

#ifndef SECRETS_H
#define SECRETS_H

#define USERNAME "your_username"
#define DEVICE_ID "your_device"
#define DEVICE_CREDENTIAL "your_credential"

#define WIFI_SSID "your_wifi"
#define WIFI_PASSWORD "your_password"

#endif

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Gas PPM Calculation

The CO concentration is calculated using the MQ-9 sensor resistance model:

Rs = (3.3 - Vout) * RL / Vout
ratio = Rs / R0
ppm = 1000 * pow(ratio, -1.5)

Where:

Value	Description
RL	Sensor load resistance (10 kΩ)
R0	Calibrated baseline resistance

NOTE: This measurement is approximate — calibration improves accuracy.

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OLED Interface

Display Sections

• Temperature (°C)
• Humidity (%)
• CO ppm
• ALERT indicator when threshold exceeded

The UI layout uses dynamic text centering and split-screen visualization.

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Setup Instructions

1. Install required Arduino libraries:
   • Adafruit SSD1306
   • Adafruit GFX
   • DHT sensor library
   • ThingerESP8266
2. Create secrets.h
3. Upload code to ESP8266
4. Configure device in Thinger.io
5. Create Email Endpoint
6. Add Dashboard widgets

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Threshold Logic

if (currentPPM > gasThreshold && !alertSent)

• Prevents alert spamming
• Resets when ppm returns to safe range
• Configurable remotely (200–500 ppm range)

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Engineering Considerations

• Non-blocking loop using millis()
• Edge-side alert logic
• Payload-based endpoint invocation
• Resource-based Cloud API
• Separation of configuration and logic
• Memory-efficient design for ESP8266

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License

This project is licensed under the MIT License.

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Final Note

This project demonstrates a full-stack IoT pipeline:

Sensor → Embedded Processing → Cloud API → Dashboard → Automated Notification

It is suitable for:

• Academic IoT demonstrations
• Smart home gas monitoring
• Industrial safety prototyping
• Cloud-connected embedded system portfolios