Air Quality AQI Monitor: PMS5003 Dust Sensor Project

Air Quality AQI Monitor: PMS5003 Dust Sensor Project

India has 9 of the world’s 10 most polluted cities by PM2.5 levels, making an AQI monitor with PMS5003 dust sensor one of the most practically valuable Arduino/ESP32 projects for Indian makers. The PMS5003 from Plantower measures PM1.0, PM2.5, and PM10 particulate matter using laser light scattering with laboratory-grade accuracy. This guide covers complete wiring, firmware, AQI calculation using India’s CPCB standards, and IoT-connected air quality monitoring for homes and workplaces.

India’s Air Quality Crisis and AQI Standards

India’s Central Pollution Control Board (CPCB) defines the National Ambient Air Quality Standards (NAAQS) and the Air Quality Index (AQI). Unlike WHO guidelines, India’s AQI uses 8 pollutants: PM2.5, PM10, NO₂, SO₂, CO, O₃, NH₃, and Pb. For DIY monitors, PM2.5 and PM10 are the most practically measurable.

PMS5003 Sensor Specifications

• Particle size measured: PM1.0, PM2.5, PM10 (µg/m³)
• Measurement range: 0-500 µg/m³ (0-1000 µg/m³ max)
• Accuracy: ±10 µg/m³ @ PM2.5 < 100 µg/m³; ±10% above
• Interface: UART 9600 baud (3.3V TTL)
• Supply voltage: 5V ± 0.5V
• Current: 100mA typical (fan motor), 200mA peak
• Response time: ≤10 seconds to stable reading
• Operating temperature: -10°C to 60°C (covers all Indian conditions)
• Lifetime: >3 years (fan-based design, monitor fan noise for end-of-life)
• India price: ₹800-1400

UART Wiring with Arduino and ESP32

/* PMS5003 Wiring
 *
 * PMS5003 Pin  Color  Arduino (SW Serial)  ESP32
 * VCC          Purple  5V                   5V (use USB power)
 * GND          Purple  GND                  GND
 * SET          White   Digital 7 (optional)  GPIO 5 (optional)
 * RXD          White   Pin 10 (SoftSerial)  GPIO 17 (UART2 TX)
 * TXD          White   Pin 11 (SoftSerial)  GPIO 16 (UART2 RX)
 * RESET        White   Optional             Optional
 * NC           Green   Not connected        Not connected
 * NC           Green   Not connected        Not connected
 *
 * WARNING: PMS5003 uses 3.3V logic on UART, NOT 5V!
 * If using Arduino 5V: Add 1kΩ voltage divider on TXD line
 *   PMS5003 TXD → 1kΩ → Arduino pin
 *                      → 2kΩ → GND
 * (This divides 3.3V to 2.2V, still reads as HIGH on Arduino)
 *
 * ESP32: Direct connection (both use 3.3V UART)
 */

PMS5003 Data Protocol and Parsing

// PMS5003 Arduino Code with AQI Calculation
// Using SoftwareSerial for Arduino Uno (limited RAM for full parsing)
// For Arduino Mega or ESP32: use hardware Serial1/Serial2

#include <SoftwareSerial.h>

SoftwareSerial pmsSerial(11, 10); // RX, TX

struct PMS5003Data {
  uint16_t PM_SP_UG_1_0;   // Standard particle PM1.0 (µg/m³)
  uint16_t PM_SP_UG_2_5;   // Standard particle PM2.5
  uint16_t PM_SP_UG_10_0;  // Standard particle PM10
  uint16_t PM_AE_UG_1_0;   // Atmospheric environment PM1.0
  uint16_t PM_AE_UG_2_5;   // Atmospheric environment PM2.5 (use this!)
  uint16_t PM_AE_UG_10_0;  // Atmospheric environment PM10 (use this!)
  uint16_t particle_0_3;   // Particles >0.3µm per 0.1L
  uint16_t particle_0_5;
  uint16_t particle_1_0;
  uint16_t particle_2_5;
  uint16_t particle_5_0;
  uint16_t particle_10_0;
};

PMS5003Data data;

bool readPMS5003() {
  // PMS5003 frame: 0x42 0x4D + 28 bytes data + 2 bytes checksum = 32 bytes total
  if (pmsSerial.available() < 32) return false;
  
  // Find frame start
  if (pmsSerial.read() != 0x42) return false;
  if (pmsSerial.read() != 0x4D) return false;
  
  // Read 28 data bytes + 2 checksum
  uint8_t buf[28];
  uint16_t checksum = 0x42 + 0x4D;
  
  for (int i = 0; i < 28; i++) {
    buf[i] = pmsSerial.read();
    if (i < 26) checksum += buf[i];
  }
  
  // Verify checksum
  uint16_t receivedChecksum = (buf[26] << 8) | buf[27];
  if (checksum != receivedChecksum) {
    Serial.println("PMS5003 checksum error!");
    return false;
  }
  
  // Parse 16-bit values (big-endian)
  data.PM_SP_UG_1_0  = (buf[2] << 8) | buf[3];
  data.PM_SP_UG_2_5  = (buf[4] << 8) | buf[5];
  data.PM_SP_UG_10_0 = (buf[6] << 8) | buf[7];
  data.PM_AE_UG_1_0  = (buf[8] << 8) | buf[9];
  data.PM_AE_UG_2_5  = (buf[10] << 8) | buf[11];
  data.PM_AE_UG_10_0 = (buf[12] << 8) | buf[13];
  
  return true;
}

void setup() {
  Serial.begin(115200);
  pmsSerial.begin(9600);
  
  Serial.println("PMS5003 AQI Monitor Ready");
  delay(5000); // Allow sensor fan to stabilize
}

void loop() {
  if (readPMS5003()) {
    int aqi_pm25 = calculateAQI_PM25(data.PM_AE_UG_2_5);
    int aqi_pm10 = calculateAQI_PM10(data.PM_AE_UG_10_0);
    int overallAQI = max(aqi_pm25, aqi_pm10); // Highest sub-index = AQI
    
    Serial.print("PM2.5: "); Serial.print(data.PM_AE_UG_2_5);
    Serial.print(" µg/m³ | PM10: "); Serial.print(data.PM_AE_UG_10_0);
    Serial.print(" µg/m³ | AQI: "); Serial.print(overallAQI);
    Serial.print(" - "); Serial.println(getAQICategory(overallAQI));
  }
  delay(2000);
}

String getAQICategory(int aqi) {
  if (aqi <= 50) return "Good";
  if (aqi <= 100) return "Satisfactory";
  if (aqi <= 200) return "Moderate";
  if (aqi <= 300) return "Poor";
  if (aqi <= 400) return "Very Poor";
  return "SEVERE - Hazardous!";
}

CPCB AQI Calculation Formula

// India CPCB AQI Calculation (sub-index formula)
// AQI = [(IHi - ILo) / (CHi - CLo)] × (Cp - CLo) + ILo
// Where: Cp = measured concentration, C/I = breakpoint table values

int calculateAQI_PM25(float pm25) {
  // CPCB PM2.5 breakpoints (24-hour average)
  // [concentration_low, concentration_high, aqi_low, aqi_high]
  float breakpoints[][4] = {
    {0, 30, 0, 50},       // Good
    {30.1, 60, 51, 100},  // Satisfactory
    {60.1, 90, 101, 200}, // Moderate
    {90.1, 120, 201, 300}, // Poor
    {120.1, 250, 301, 400}, // Very Poor
    {250.1, 1000, 401, 500} // Severe
  };
  
  for (int i = 0; i = breakpoints[i][0] && pm25 <= breakpoints[i][1]) {
      float aqi = ((breakpoints[i][3] - breakpoints[i][2]) /
                   (breakpoints[i][1] - breakpoints[i][0])) *
                  (pm25 - breakpoints[i][0]) + breakpoints[i][2];
      return (int)aqi;
    }
  }
  return 500; // Beyond scale
}

int calculateAQI_PM10(float pm10) {
  float breakpoints[][4] = {
    {0, 50, 0, 50},
    {50.1, 100, 51, 100},
    {100.1, 250, 101, 200},
    {250.1, 350, 201, 300},
    {350.1, 430, 301, 400},
    {430.1, 1000, 401, 500}
  };
  for (int i = 0; i = breakpoints[i][0] && pm10 <= breakpoints[i][1]) {
      float aqi = ((breakpoints[i][3] - breakpoints[i][2]) /
                   (breakpoints[i][1] - breakpoints[i][0])) *
                  (pm10 - breakpoints[i][0]) + breakpoints[i][2];
      return (int)aqi;
    }
  }
  return 500;
}

IoT Dashboard with ThingSpeak

// ESP32 PMS5003 + ThingSpeak IoT Dashboard
// Free ThingSpeak account: 3 million messages/year
// Update interval: Every 15 seconds minimum (ThingSpeak limit)

#include <WiFi.h>
#include <HTTPClient.h>

#define THINGSPEAK_KEY "YOUR_WRITE_API_KEY"
const char* ssid = "YOUR_WIFI";
const char* password = "YOUR_PASSWORD";

void sendToThingSpeak(float pm25, float pm10, int aqi) {
  if (WiFi.status() != WL_CONNECTED) return;
  
  HTTPClient http;
  String url = "http://api.thingspeak.com/update?api_key=";
  url += THINGSPEAK_KEY;
  url += "&field1=" + String(pm25, 1);
  url += "&field2=" + String(pm10, 1);
  url += "&field3=" + String(aqi);
  
  http.begin(url);
  int httpCode = http.GET();
  if (httpCode == 200) {
    Serial.println("ThingSpeak updated!");
  }
  http.end();
}
// Visualize at: https://thingspeak.com/channels/YOUR_CHANNEL_ID
// Share public URL with neighbors for community monitoring

Sensor Enclosure and Deployment Tips

Proper enclosure is critical for outdoor PMS5003 deployment in India’s harsh climate:

• Gill screen: Use a radiation/solar shield around the sensor to prevent direct sunlight heating (which falsely elevates readings). Commercial radiation shields cost ₹500-800; DIY with white PVC pipe sections works equally well.
• Fan orientation: PMS5003 has a built-in fan. Mount with air inlet facing downward (prevents rain ingress) and outlet facing down-wind.
• Monsoon protection: Add Gore-Tex or PTFE membrane filter over air inlet to block humidity above 85% RH — PMS5003 overreads PM at high humidity due to hygroscopic particle growth.
• Height: Mount at 1.5-2m above ground (breathing height) for human exposure monitoring; 10m above ground for ambient air quality comparison with CPCB stations.

Frequently Asked Questions