Circuit Documentation

Summary

This circuit is designed to monitor air quality by measuring temperature, humidity, gas concentration, and dust density. It uses an Arduino UNO microcontroller to process sensor data and display the results on an OLED screen. The circuit also includes LEDs and a buzzer to provide visual and auditory alerts based on the air quality index (AQI).

Component List

1. Arduino UNO

   • Description: Microcontroller board based on the ATmega328P.
   • Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0, A1, A2, A3, A4, A5, SCL, SDA, AREF, D13, D12, D11, D10, D9, D8, D7, D6, D5, D4, D3, D2, D1, D0

2. GP2Y1010AU0F

   • Description: Optical dust sensor.
   • Pins: VCC, Vout, S-GND, LED, LED-GND, V-LED

3. Resistor

   • Description: 100 Ohms resistor.
   • Pins: pin1, pin2
   • Properties: Resistance = 100 Ohms

4. Electrolytic Capacitor

   • Description: 47 µF capacitor.
   • Pins: -, +
   • Properties: Capacitance = 47 µF

5. LED: Two Pin (yellow)

   • Description: Yellow LED.
   • Pins: cathode, anode

6. LED: Two Pin (green)

   • Description: Green LED.
   • Pins: cathode, anode

7. LED: Two Pin (red)

   • Description: Red LED.
   • Pins: cathode, anode

8. OLED 1.3"

   • Description: 1.3-inch OLED display.
   • Pins: GND, VCC, SCL, SDA

9. DHT22

   • Description: Temperature and humidity sensor.
   • Pins: +, Out, -

10. MQ 135

    • Description: Gas sensor.
    • Pins: D OUT, A OUT, GND, VCC

11. Buzzer

    • Description: Piezoelectric buzzer.
    • Pins: PIN, GND

Wiring Details

Arduino UNO

• 5V: Connected to VCC of GP2Y1010AU0F, pin1 of Resistor, VCC of MQ 135, + of DHT22, VCC of OLED 1.3"
• GND: Connected to S-GND and LED-GND of GP2Y1010AU0F, GND of MQ 135, GND of Buzzer, - of DHT22, cathode of red LED, cathode of yellow LED, GND of OLED 1.3", cathode of green LED
• A0: Connected to A OUT of MQ 135
• A1: Connected to Vout of GP2Y1010AU0F
• A4: Connected to SDA of OLED 1.3"
• A5: Connected to SCL of OLED 1.3"
• D2: Connected to Out of DHT22
• D3: Connected to LED of GP2Y1010AU0F
• D6: Connected to anode of red LED, anode of yellow LED, anode of green LED
• D7: Connected to PIN of Buzzer

GP2Y1010AU0F

• VCC: Connected to 5V of Arduino UNO
• Vout: Connected to A1 of Arduino UNO
• S-GND: Connected to GND of Arduino UNO
• LED: Connected to D3 of Arduino UNO
• LED-GND: Connected to GND of Arduino UNO
• V-LED: Connected to pin2 of Resistor, - of Electrolytic Capacitor

Resistor

• pin1: Connected to 5V of Arduino UNO
• pin2: Connected to V-LED of GP2Y1010AU0F, - of Electrolytic Capacitor

Electrolytic Capacitor

• +: Connected to GND of Arduino UNO
• -: Connected to pin2 of Resistor, V-LED of GP2Y1010AU0F

LED: Two Pin (yellow)

• cathode: Connected to GND of Arduino UNO
• anode: Connected to D6 of Arduino UNO

LED: Two Pin (green)

• cathode: Connected to GND of Arduino UNO
• anode: Connected to D6 of Arduino UNO

LED: Two Pin (red)

• cathode: Connected to GND of Arduino UNO
• anode: Connected to D6 of Arduino UNO

OLED 1.3"

• GND: Connected to GND of Arduino UNO
• VCC: Connected to 5V of Arduino UNO
• SCL: Connected to A5 of Arduino UNO
• SDA: Connected to A4 of Arduino UNO

DHT22

• +: Connected to 5V of Arduino UNO
• Out: Connected to D2 of Arduino UNO
• -: Connected to GND of Arduino UNO

MQ 135

• D OUT: Not connected
• A OUT: Connected to A0 of Arduino UNO
• GND: Connected to GND of Arduino UNO
• VCC: Connected to 5V of Arduino UNO

Buzzer

• PIN: Connected to D7 of Arduino UNO
• GND: Connected to GND of Arduino UNO

Code Documentation

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include "DHT.h"

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define DHTPIN 2
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

#define MQ135_PIN A0
#define DUST_SENSOR_LED 3
#define DUST_SENSOR_OUT A1

#define GREEN_LED 4
#define YELLOW_LED 5
#define RED_LED 6
#define BUZZER 7

void setup() {
    Serial.begin(9600);
    dht.begin();

    if (!display.begin(0x3C)) {
        Serial.println(F("SSD1306 allocation failed"));
        for (;;);
    }
    display.display();
    delay(2000);
    display.clearDisplay();

    pinMode(DUST_SENSOR_LED, OUTPUT);
    pinMode(GREEN_LED, OUTPUT);
    pinMode(YELLOW_LED, OUTPUT);
    pinMode(RED_LED, OUTPUT);
    pinMode(BUZZER, OUTPUT);

    digitalWrite(GREEN_LED, LOW);
    digitalWrite(YELLOW_LED, LOW);
    digitalWrite(RED_LED, LOW);
    digitalWrite(BUZZER, LOW);
}

void loop() {
    float humidity = dht.readHumidity();
    float temperatureC = dht.readTemperature();
    if (isnan(humidity) || isnan(temperatureC)) {
        Serial.println("Failed to read from DHT sensor!");
        return;
    }
    int mq135_value = analogRead(MQ135_PIN);
    float gasQuality = map(mq135_value, 0, 1023, 0, 500);

    digitalWrite(DUST_SENSOR_LED, LOW);
    delayMicroseconds(280);
    int dustValue = analogRead(DUST_SENSOR_OUT);
    digitalWrite(DUST_SENSOR_LED, HIGH);
    delayMicroseconds(9680);

    float dustDensity = (dustValue - 500) * 0.5;
    float combinedAQI = (gasQuality + dustDensity) / 2;

    Serial.print("Temp: "); Serial.print(temperatureC); Serial.print(" C, ");
    Serial.print("Humidity: "); Serial.print(humidity); Serial.print(" %, ");
    Serial.print("Gas AQI: "); Serial.print(gasQuality);
    Serial.print(", Dust Density: "); Serial.print(dustDensity);
    Serial.print(" ug/m3, Combined AQI: "); Serial.println(combinedAQI);

    if (combinedAQI <= 50) {
        digitalWrite(GREEN_LED, HIGH);
        digitalWrite(YELLOW_LED, LOW);
        digitalWrite(RED_LED, LOW);
        digitalWrite(BUZZER, LOW);
    } else if (combinedAQI > 50 && combinedAQI <= 150) {
        digitalWrite(GREEN_LED, LOW);
        digitalWrite(YELLOW_LED, HIGH);
        digitalWrite(RED_LED, LOW);
        digitalWrite(BUZZER, LOW);
    } else {
        digitalWrite(GREEN_LED, LOW);
        digitalWrite(YELLOW_LED, LOW);
        digitalWrite(RED_LED, HIGH);
        digitalWrite(BUZZER, HIGH);
    }

    display.clearDisplay();
    display.setTextSize