Arduino Dust Sensor with ESP8266

June 14, 2015July 23, 2015 shadowandy Arduino, Dust Sensor, ESP8266, PPD42NS, Shinyei

Comparing the size of ESP8266 with a SD Card

The ESP8266 comes in various packages (e.g. ESP-12, ESP-07) but I bought the (pretty) bare package for less than US$2.50. For this price, the ESP8266 (ESP-01) has got 80 MHz CPU, 512KB program storage space, WiFi and 2 GPIOs. This tiny Arduino board is very suitable for Internet-of-Things (IoT) implementations.

With this, I decided to rebuild my previous Arduino-based Dust Sensor. The codes for the ESP8266 is as follow.

/**********************************************/
/* Building Arduino Dust Sensor using:        */
/*      - ESP8266 ESP-01                      */
/*      - 3.3-to-5v Logic Level Converter     */
/*      - Shinyei PPD42NS                     */
/* http://www.sca-shinyei.com/pdf/PPD42NS.pdf */
/*                                            */
/* Author: shadowandy[dot]sg[at]gmail[dot]com */
/* Web: www.shadowandy.net                    */
/*                                            */         
/* Wiring Instruction:                        */
/*      - PPD42NS Pin 1 => GND                */
/*      - PPD42NS Pin 2 => GPIO0              */
/*      - PPD42NS Pin 3 => 5V                 */
/*      - PPD42NS Pin 4 => GPIO2              */
/**********************************************/

#include <ESP8266WiFi.h>                 

const char ssid[] = "fill in your wireless SSID";
const char pass[] = "fill in your wireless pass";
const char thingSpeakAddress[] = "api.thingspeak.com";
const char thingSpeakAPIKey[] = "fill in your thingspeak API write key";

#define PM25 0
#define PM10 1
int pin[] = {2, 0};
unsigned long starttime;
unsigned long sampletime_ms = 30000;
unsigned long triggerOn[2];
unsigned long triggerOff[2];
unsigned long lowpulseoccupancy[] = {0, 0};
float ratio[] = {0, 0};
float count[] = {0, 0};
boolean value[] = {HIGH, HIGH};
boolean trigger[] = {false, false};

void setup() {
  connectWiFi();
  pinMode(pin[PM25], INPUT); //Listen at the designated PIN
  pinMode(pin[PM10], INPUT); //Listen at the designated PIN
  starttime = millis(); //Fetching the current time
  ESP.wdtEnable(WDTO_8S); // Enabling Watchdog
}

void loop() {
  value[PM25] = digitalRead(pin[PM25]);
  value[PM10] = digitalRead(pin[PM10]);

  if (value[PM25] == LOW && trigger[PM25] == false) {
    trigger[PM25] = true;
    triggerOn[PM25] = micros();
  }
  if (value[PM25] == HIGH && trigger[PM25] == true) {
    triggerOff[PM25] = micros();
    lowpulseoccupancy[PM25] += (triggerOff[PM25] - triggerOn[PM25]);
    trigger[PM25] = false;
  }
  if (value[PM10] == LOW && trigger[PM10] == false) {
    trigger[PM10] = true;
    triggerOn[PM10] = micros();
  }
  if (value[PM10] == HIGH && trigger[PM10] == true) {
    triggerOff[PM10] = micros();
    lowpulseoccupancy[PM10] += (triggerOff[PM10] - triggerOn[PM10]);
    trigger[PM10] = false;
  }
  ESP.wdtFeed(); // Reset the WatchDog
  
  if ((millis() - starttime) > sampletime_ms) //Checking if it is time to sample
  {
    ratio[PM25] = lowpulseoccupancy[PM25] / (sampletime_ms * 10.0);
    count[PM25] = 1.1 * pow(ratio[PM25], 3) - 3.8 * pow(ratio[PM25], 2) + 520 * ratio[PM25] + 0.62;
    ratio[PM10] = lowpulseoccupancy[PM10] / (sampletime_ms * 10.0);
    count[PM10] = 1.1 * pow(ratio[PM10], 3) - 3.8 * pow(ratio[PM10], 2) + 520 * ratio[PM10] + 0.62;
    count[PM25] -= count[PM10];
    
    ESP.wdtFeed(); // Reset the WatchDog
    // Begin mass concentration calculation
    float concentration[] = {0, 0};
    double pi = 3.14159;
    double density = 1.65 * pow(10, 12);
    double K = 3531.5;
    
    ESP.wdtFeed(); // Reset the WatchDog
    // PM10
    double r10 = 2.6 * pow(10, -6);
    double vol10 = (4 / 3) * pi * pow(r10, 3);
    double mass10 = density * vol10;
    concentration[PM10] = (count[PM10]) * K * mass10;
    
    ESP.wdtFeed(); // Reset the WatchDog
    // PM2.5
    double r25 = 0.44 * pow(10, -6);
    double vol25 = (4 / 3) * pi * pow(r25, 3);
    double mass25 = density * vol25;
    concentration[PM25] = (count[PM25]) * K * mass25;
    // End of mass concentration calculation

    ESP.wdtFeed(); // Reset the WatchDog
    
    connectWiFi();
    updateThingSpeak("1=" + String(concentration[PM10], DEC) + "&2=" + String(count[PM10], DEC) + "&3=" + String(concentration[PM25], DEC) + "&4=" + String(count[PM25], DEC));
    // Resetting for next sampling
    lowpulseoccupancy[PM25] = 0;
    lowpulseoccupancy[PM10] = 0;
    starttime = millis();
    ESP.wdtFeed(); // Reset the WatchDog
  }
}

void connectWiFi() {
  if (WiFi.status() == WL_CONNECTED) {
    return;
  }
  WiFi.begin(ssid, pass);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
  }
}

void updateThingSpeak(String tsData) {
  WiFiClient client;
  if (!client.connect(thingSpeakAddress, 80)) {
    return;
  }
  client.print(F("GET /update?key="));
  client.print(thingSpeakAPIKey);
  client.print(F("&"));
  client.print(tsData);
  client.print(F(" HTTP/1.1\r\nHost: api.thingspeak.com\r\n\r\n"));
  client.println();
}

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/**********************************************/

/* Building Arduino Dust Sensor using: */

/* - ESP8266 ESP-01 */

/* - 3.3-to-5v Logic Level Converter */

/* - Shinyei PPD42NS */

/* http://www.sca-shinyei.com/pdf/PPD42NS.pdf */

/* */

/* Author: shadowandy[dot]sg[at]gmail[dot]com */

/* Web: www.shadowandy.net */

/* */

/* Wiring Instruction: */

/* - PPD42NS Pin 1 => GND */

/* - PPD42NS Pin 2 => GPIO0 */

/* - PPD42NS Pin 3 => 5V */

/* - PPD42NS Pin 4 => GPIO2 */

/**********************************************/

#include <ESP8266WiFi.h>

const char ssid[] = "fill in your wireless SSID";

const char pass[] = "fill in your wireless pass";

const char thingSpeakAddress[] = "api.thingspeak.com";

const char thingSpeakAPIKey[] = "fill in your thingspeak API write key";

#define PM25 0

#define PM10 1

int pin[] = {2, 0};

unsigned long starttime;

unsigned long sampletime_ms = 30000;

unsigned long triggerOn[2];

unsigned long triggerOff[2];

unsigned long lowpulseoccupancy[] = {0, 0};

float ratio[] = {0, 0};

float count[] = {0, 0};

boolean value[] = {HIGH, HIGH};

boolean trigger[] = {false, false};

void setup() {

connectWiFi();

pinMode(pin[PM25], INPUT); //Listen at the designated PIN

pinMode(pin[PM10], INPUT); //Listen at the designated PIN

starttime = millis(); //Fetching the current time

ESP.wdtEnable(WDTO_8S); // Enabling Watchdog

}

void loop() {

value[PM25] = digitalRead(pin[PM25]);

value[PM10] = digitalRead(pin[PM10]);

if (value[PM25] == LOW && trigger[PM25] == false) {

trigger[PM25] = true;

triggerOn[PM25] = micros();

}

if (value[PM25] == HIGH && trigger[PM25] == true) {

triggerOff[PM25] = micros();

lowpulseoccupancy[PM25] += (triggerOff[PM25] - triggerOn[PM25]);

trigger[PM25] = false;

}

if (value[PM10] == LOW && trigger[PM10] == false) {

trigger[PM10] = true;

triggerOn[PM10] = micros();

}

if (value[PM10] == HIGH && trigger[PM10] == true) {

triggerOff[PM10] = micros();

lowpulseoccupancy[PM10] += (triggerOff[PM10] - triggerOn[PM10]);

trigger[PM10] = false;

}

ESP.wdtFeed(); // Reset the WatchDog

if ((millis() - starttime) > sampletime_ms) //Checking if it is time to sample

{

ratio[PM25] = lowpulseoccupancy[PM25] / (sampletime_ms * 10.0);

count[PM25] = 1.1 * pow(ratio[PM25], 3) - 3.8 * pow(ratio[PM25], 2) + 520 * ratio[PM25] + 0.62;

ratio[PM10] = lowpulseoccupancy[PM10] / (sampletime_ms * 10.0);

count[PM10] = 1.1 * pow(ratio[PM10], 3) - 3.8 * pow(ratio[PM10], 2) + 520 * ratio[PM10] + 0.62;

count[PM25] -= count[PM10];

ESP.wdtFeed(); // Reset the WatchDog

// Begin mass concentration calculation

float concentration[] = {0, 0};

double pi = 3.14159;

double density = 1.65 * pow(10, 12);

double K = 3531.5;

ESP.wdtFeed(); // Reset the WatchDog

// PM10

double r10 = 2.6 * pow(10, -6);

double vol10 = (4 / 3) * pi * pow(r10, 3);

double mass10 = density * vol10;

concentration[PM10] = (count[PM10]) * K * mass10;

ESP.wdtFeed(); // Reset the WatchDog

// PM2.5

double r25 = 0.44 * pow(10, -6);

double vol25 = (4 / 3) * pi * pow(r25, 3);

double mass25 = density * vol25;

concentration[PM25] = (count[PM25]) * K * mass25;

// End of mass concentration calculation

ESP.wdtFeed(); // Reset the WatchDog

connectWiFi();

updateThingSpeak("1=" + String(concentration[PM10], DEC) + "&2=" + String(count[PM10], DEC) + "&3=" + String(concentration[PM25], DEC) + "&4=" + String(count[PM25], DEC));

// Resetting for next sampling

lowpulseoccupancy[PM25] = 0;

lowpulseoccupancy[PM10] = 0;

starttime = millis();

ESP.wdtFeed(); // Reset the WatchDog

}

void connectWiFi() {

if (WiFi.status() == WL_CONNECTED) {

return;

}

WiFi.begin(ssid, pass);

while (WiFi.status() != WL_CONNECTED) {

delay(500);

}

void updateThingSpeak(String tsData) {

WiFiClient client;

if (!client.connect(thingSpeakAddress, 80)) {

return;

}

client.print(F("GET /update?key="));

client.print(thingSpeakAPIKey);

client.print(F("&"));

client.print(tsData);

client.print(F(" HTTP/1.1\r\nHost: api.thingspeak.com\r\n\r\n"));

client.println();

}

The periodically updated codes can be found on Github – Arduino Dust Sensor.

5 thoughts on “Arduino Dust Sensor with ESP8266”

pacraf
November 23, 2016 at 5:17 pm
Hi,
Thank you for sharing the project.
It’s already a while since you did the project.
Could you comment on it? Is ESP reliable enough to deal with sensor? I read on tne net some comments, that ESP have some trouble with arduino/nodemcu scripts , it’s sometimes not starting up, sometimes freezes. I wonder if you face this trouble too. I would like to build few of those monitoring stations, and wonder which platform for dealing with sensor will be better (ESP or Arduino with wifi shield… ) Please advice. The purpose is to install few stations in my neighborhood streets, with big displays, to inform people about air quality (you know, here in Poland we still burn lot of coal to heat houses… it’s sometimes hard to breathe). Networking capability will be used to record data and map data for later use…
kind regards, pacraf
Andy
November 24, 2016 at 3:09 pm
Hi pacraf,
Yes, the ESP8266 can be unreliable at times. I have added decoupling capacitor to the ESP8266 which made it slightly more stable but it still freezes randomly which I have no idea what happened to it. For actual production deployment, I would recommend getting a Arduino with WiFi shield.
If you have managed to locate a Node.JS application that interfaces well with the air quality sensor (via the GPIO), then you might want to consider using Raspberry Pi (with Node.JS). Recommending this because you will be able to easily hook up a display (i.e. display) to the HDMI output of Raspberry Pi. You can also easily make use of common React or AngularJS frameworks to craft up a nice UI for display.
Ben Sijtsma
January 1, 2017 at 11:36 pm
Hi, many thanks for sharing.
I think your code could contain a small but significant error: Line 88 should read
double vol10 = (4.0 / 3.0) * pi * pow(r10, 3);
Since (4/3) is integer division, yielding 1, and (4.0/3.0) is double division, yielding 1.3333, the value you want.
Same holds for line 95.
The Admin
February 2, 2017 at 10:41 pm
Hi,
I have an issue with reading from sensor. The calculation is always the same:
Concentration pm10: 0.27
Concentration pm25: 0.00
Count pm10: 0.62
Count pm25: 0.00
The only thing different from your installation is that I’m using NodeMCU ESP8266-12E board. Everything else is the same (wiring, sensor, llc).
Any suggestions how to debug?