Edoardo Mazzone
Published © CC BY-NC-SA

Air Quality ESP32: Build a Portable IoT Sensor

The idea behind this project was to create a device easily reproducible for measuring air pollution with ESP32 and a live dashboard.

IntermediateWork in progress10 hours6,853
Air Quality ESP32: Build a Portable IoT Sensor

Things used in this project

Hardware components

ESP32 DEVKIT V1 board
×1
Nova SDS011 PM10/2.5 sensor
×1
DC/DC step-up converter
×1
MHZ-19 CO2 sensor
×1
DHT11 Temperature & Humidity Sensor (3 pins)
DHT11 Temperature & Humidity Sensor (3 pins)
×1
3V7 1000 mAh LiPo battery
×1

Software apps and online services

Arduino IDE
Arduino IDE
InfluxDB

Hand tools and fabrication machines

3D Printer (generic)
3D Printer (generic)

Story

Read more

Custom parts and enclosures

Case Development

Sketchfab still processing.

Case top

You can decide either to print (4mm) or woodcut the top of the case

Schematics

Gerber file

Code

Air Quality Sensor

Arduino
/*
  Mazzone Edoardo
  Complete project details at "https://github.com/edomazzone" (instrucatbles che pubblico)

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files.

  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
*/

//include all library

#include <MHZ19.h>
#include <Arduino.h>
#include <WiFi.h>
#include <AsyncTCP.h>
#include <ESPAsyncWebServer.h>
#include <AsyncElegantOTA.h>
#include <SDS011.h>
#include <SPIFFS.h>
#include <DHT.h>
#include <WiFiMulti.h>
#include <InfluxDbClient.h>
#include <InfluxDbCloud.h>
#include <esp_sleep.h>

/******************************************************/
//MHZ-19

#define RX_PIN 26                                          // Rx pin which the MHZ19 Tx pin is attached to
#define TX_PIN 27                                          // Tx pin which the MHZ19 Rx pin is attached to
#define BAUDRATE 9600                                      // Device to MH-Z19 Serial baudrate (should not be changed)#include <Arduino.h>

MHZ19 myMHZ19;                                             // Constructor for library
HardwareSerial mySerial(1);                                // On ESP32 we do not require the SoftwareSerial library, since we have 2 USARTS available

unsigned long getDataTimer;
unsigned long preheat_time = 15000;     //test time
int CO2;

/******************************************************/
//OTA

const char* ssid = "xxxxxxxxxxxxxxxxx";
const char* password = "yyyyyyyyyyyyyy";

AsyncWebServer server(80);

/******************************************************/
//SDS011

float p10, p25;
int err;
SDS011 my_sds;
#ifdef ESP32
HardwareSerial port(2);
#endif

/******************************************************/
//DHT11

#define DHTPIN 5
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

/******************************************************/
//InfluxDB

WiFiMulti wifiMulti;
#define DEVICE "ESP32"

#define WIFI_SSID "xxxxxxxxxxxxxxxxxx"
#define WIFI_PASSWORD "yyyyyyyyyyyyyyyyyyyyy"

#define INFLUXDB_URL "https://us-east-1-1.aws.cloud2.influxdata.com"
#define INFLUXDB_TOKEN "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
#define INFLUXDB_ORG "zzzzzzzzzz"
#define INFLUXDB_BUCKET "Sensor"
// Set timezone string according to https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
//  Central Europe: "CET-1CEST,M3.5.0,M10.5.0/3"
#define TZ_INFO "UTC2"
InfluxDBClient client(INFLUXDB_URL, INFLUXDB_ORG, INFLUXDB_BUCKET, INFLUXDB_TOKEN, InfluxDbCloud2CACert);
Point sensor_readings("measurements");

/**************************************/
//Global var

byte i;
unsigned long s = 30;
double Temp;
#define uS_TO_S_FACTOR 1000000    // Conversion factor for micro seconds to seconds 
#define TIME_TO_SLEEP  300        // Time ESP32 will go to sleep (in seconds) 5min*60s
int interval = 5000;              //start time for PM sensor


void setup() {
  Serial.begin(9600);                                            // Start serial monitor
  esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR); // Set sleep time

  WiFi.mode(WIFI_STA);                                           //Turn on WiFi
  wifiMulti.addAP(WIFI_SSID, WIFI_PASSWORD);

  Serial.print("Connecting to wifi");
  while ((wifiMulti.run() != WL_CONNECTED) && (i < 5)) {
    i++;
    Serial.print(".");
    delay(500);
  }
  Serial.println("");
  Serial.print("Connected to ");
  Serial.println(WIFI_SSID);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP()); //remember to connect at same SSID

  server.on("/", HTTP_GET, [](AsyncWebServerRequest * request) {
    request->send(200, "text/plain", "AirQualitySensor");
  });

  AsyncElegantOTA.begin(&server);    // Start ElegantOTA
  server.begin();
  Serial.println("HTTP server started");

  // Add tags
  sensor_readings.addTag("sensor", "Green");  //if you are using more sensor (we chose case color)

  // Alternatively, set insecure connection to skip server certificate validation
  //client.setInsecure();

  timeSync(TZ_INFO, "pool.ntp.org", "time.nis.gov");

  // Check server connection
  if (client.validateConnection()) {
    Serial.print("Connected to InfluxDB: ");
    Serial.println(client.getServerUrl());
  } else {
    Serial.print("InfluxDB connection failed: ");
    Serial.println(client.getLastErrorMessage());
  }

  mySerial.begin(BAUDRATE, SERIAL_8N1, RX_PIN, TX_PIN);    // device to MH-Z19 serial start
  myMHZ19.begin(mySerial);                                // *Serial(Stream) reference must be passed to library begin().
  myMHZ19.setRange(2000);
  myMHZ19.autoCalibration();                              // Turn auto calibration ON (OFF autoCalibration(false))
  my_sds.begin(&port);
  dht.begin();

  if (!SPIFFS.begin(true)) {
    Serial.println("An Error has occurred while mounting SPIFFS");
    return;
  }
}

void loop() {
  //Print not sended data
  File file2 = SPIFFS.open("/PM sensor.txt");
  if (!file2) {
    Serial.println("Failed to open file for reading");
    return;
  }
  Serial.println("File Content:");
  while (file2.available()) {
    Serial.write(file2.read());
  }
  file2.close();

  //retrieve new data
  sds_011.wakeup();
  delay(interval);
  err = my_sds.read(&p25, &p10);                    // Request PM values
  if (!err) {
    Serial.print("P2.5: " + String(p25));
    Serial.println("  P10:  " + String(p10));
  }
  else{
        Serial.println("Error PM READINGS!!");
  }
  sds_011.sleep();

  CO2 = myMHZ19.getCO2();                             // Request CO2 (as ppm)
  Temp = myMHZ19.getTemperature();                    // Request Temperature (as Celsius)
  Serial.print("CO2 (ppm): ");
  Serial.print(CO2);
  Serial.print(" Temperature (C): ");
  Serial.println(Temp);

  double h = dht.readHumidity();
  double t = dht.readTemperature();

  if (isnan(h) || isnan(t)) {                             // Check if any reads failed
    Serial.println("Error TEMPERATURE SENSOR!!");
  }

  // Compute heat index in Celsius (isFahreheit = false)
  //float hic = dht.computeHeatIndex(t, h, false);
  Serial.print(F("Humidity: "));
  Serial.print(h);
  Serial.print(F("%  Temperature: "));
  Serial.print(t);
  Serial.println(F("C "));
  Serial.println("");
  Serial.println("-----------------------");
  Serial.println("");

  //Send data to InfluxDB
  sensor_readings.clearFields();
  sensor_readings.addField("rssi", WiFi.RSSI());
  sensor_readings.addField("temperature", t);   //Get Data from temperature sensor
  sensor_readings.addField("co2", CO2);                //Get Data from from co2 sensor
  sensor_readings.addField("humidity", h);             //Get Data from humidity sensor
  sensor_readings.addField("pm2_5", p25);              //Get PM2_5
  sensor_readings.addField("pm10", p10);               //Get PM10

  Serial.print("Writing: ");
  Serial.println(client.pointToLineProtocol(sensor_readings));
  if (wifiMulti.run() != WL_CONNECTED) {
    Serial.println("Wifi connection lost");
  }
  // Write point
  if (!client.writePoint(sensor_readings)) {
    Serial.print("InfluxDB write failed: ");
    Serial.println(client.getLastErrorMessage());

    //if WiFi not works save in the SPIFFS
    String measurements = "Time: " + String(s) + ", " + "T: " + String(Temp + 4) + ", " + "H: " + String(h) + ", " + "PM10: " + String(p10) + ", " + "PM2.5: " + String(p25) + ", " + "CO2: " + String(CO2) + ", " + + "RSSI: " + String( WiFi.RSSI()) + " \n";

    File file = SPIFFS.open("/PM sensor.txt", FILE_APPEND);
    if (!file) {
      Serial.println("There was an error opening the file for writing");
      return;
    }
    if (file.print(measurements)) {
      Serial.println("File was written");
    } else {
      Serial.println("File write failed");
    }
    file.close();
  }
  
  //start sleep
  Serial.println("Going to sleep now");
  delay(100);
  Serial.flush();
  esp_deep_sleep_start();
}

Air-Quality-Sensor-ESP32

Credits

Edoardo Mazzone

Edoardo Mazzone

1 project • 2 followers
Hi everyone! I'm an Italian engineering student passionate about electronics and developing solutions to combat climate change.

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