Read PWM on SDS011 Nova Fitness

nullsports · March 16, 2019, 7:53pm

Hello Forum,
I want to read the PWM output signals on the SDS011. Seems that this feature is rarely used. It is described here on page https://cdn-reichelt.de/documents/datenblatt/X200/SDS011-DATASHEET.pdf Page 5 to 7
It seems that I have to read in a specific timerange, but I don´t know jow to do this the right way.

I just tried reading PWM:

int pin = 14;  // Check what pin to use
int pwm_25; // Duration of the pulse

// setup serial and input, output pins
void setup()
{
 
  Serial.begin(9600);
  pinMode(pin, INPUT);

}

 

void loop()
{

  pwm_25 = pulseIn(pin, HIGH);
  Serial.println(pwm_25);
 
  delay(100); 
}

which gave me values like this:

nullsports · March 16, 2019, 8:27pm

Okay, if someone have the same Problem, here is the answer:

#define pm25Pin 12 
#define pm10Pin 13 
void setup() { 
  pinMode(pm25Pin, INPUT); 
  pinMode(pm10Pin, INPUT); 
  Serial.begin(9600); 
  } 
  
  void loop() { 
    Serial.print("PM2.5 = "); 
    Serial.println(pulseIn(pm25Pin, HIGH, 1500000) / 1000 - 2); 
    Serial.print("PM10 = "); 
 Serial.println(pulseIn(pm10Pin, HIGH, 1500000) / 1000 - 2); 
 }

Isabelkl19 · February 13, 2020, 3:19am

nullsports:
Okay, if someone have the same Problem, here is the answer:
#define pm25Pin 12 

#define pm10Pin 13
void setup() {
pinMode(pm25Pin, INPUT);
pinMode(pm10Pin, INPUT);
Serial.begin(9600);
}

void loop() {
Serial.print("PM2.5 = ");
Serial.println(pulseIn(pm25Pin, HIGH, 1500000) / 1000 - 2);
Serial.print("PM10 = ");
Serial.println(pulseIn(pm10Pin, HIGH, 1500000) / 1000 - 2);
}

It is an excellent solution, only there is a point where if you expose dust a lot the PM10 goes a little crazy. Since it marks exaggerated values without meaning, I would like to find a way to solve this.

paolometeo2 · February 27, 2020, 1:47pm

Hi everyone,
I made some comparisons between serial and PWM output from an SDS011 sensor. I found different numbers. I found PWM concentrations about 10 times less than Serial output, both for 10 and 2.5.
Did anyone find the same thing?
I used an Arduino UNO for both outputs. My code follows:

#define SSRxPin 4
#define SSTxPin 3
#define PIN10   6
#define PIN25   5
#define PAYLOAD_LEN 8
#include <SoftwareSerial.h>  // comunicazione con Feather
SoftwareSerial mySerial(SSRxPin, SSTxPin); //RX, TX   verso ARduino 
byte received[PAYLOAD_LEN];
byte i = 0;
byte ch = ' ';
byte flag = 0;
float PM10 = 0;
float PM25 = 0;
float TimePassed = 0;
float TimeOld = 0;
float Periodo = 10000;

void setup() {
  pinMode(SSTxPin, OUTPUT);
  pinMode(SSRxPin, INPUT);
  while(!mySerial);
  mySerial.begin(9600);
  delay(1000);
  while(!Serial);
  Serial.begin(115200);  // non minore di questa altrimenti si disincronizza
  delay(1000);
  Serial.println(" ProvaSDS011_Serial_PWM.ino");
}

void loop() {
  if(mySerial.available() > 0){
    ch = mySerial.read();
    Serial.print(ch,HEX);Serial.print(" ");
    if(flag){
      received[i] = ch;
      i++;
    }
    if(ch == 0xAA && !flag){
      flag = 1;
      i = 0;
    }
    if(ch == 0xAB && flag){
      flag = 0;  
      Serial.println();
      for(i = 0;i < PAYLOAD_LEN; i++){
        Serial.print(received[i]);Serial.print(" ");
      }
      Serial.println();
      int check = received[1]+received[2]+received[3]+received[4]+received[5]+received[6];
      check = check % 256;
      if(check != received[7]){
        Serial.println("   ERRORE ");
      }
      Serial.print(" check ");Serial.println(check);
      PM25 = float(received[2])*256.0 + float(received[1])/10.0;
      PM10 = float(received[4])*256.0 + float(received[3])/10.0;
      Serial.print(" PM10 ");Serial.print(PM10,1); Serial.print("  PM25 ");Serial.println(PM25,1);
    }
  }
  TimePassed = millis()-TimeOld;
  if(TimePassed > Periodo){
      unsigned long durata1 = pulseIn(PIN10,HIGH,150000000);
//      delay(5000);
      unsigned long durata2 = pulseIn(PIN25,HIGH,150000000);
      float Conc10 = float(durata1)/1000.0 - 2;  //Conc in ug/m3
      float Conc25 = float(durata2)/1000.0 - 2;  //Conc in ug/m3
      if(Conc10 < 0)Conc10 = 0;
      if(Conc25 < 0)Conc25 = 0;
      Serial.print("            ");Serial.print(durata1);Serial.print(" Conc10 ");
      Serial.print(Conc10,1);Serial.print(" ");
      Serial.print(durata2);Serial.print(" Conc25 ");Serial.print(Conc25,1);Serial.println();
      TimeOld = millis();
  }
}

Isabelkl19 · April 10, 2020, 5:23pm

I have compared the PWM output of the SDS011 sensor (code exposed here) with the results of a Aeroqual 500 series for PM10 and PM2.5 and they gave quite accurate. Actually I am amazed at the accuracy of it.

paolometeo2:
Hi everyone,
I made some comparisons between serial and PWM output from an SDS011 sensor. I found different numbers. I found PWM concentrations about 10 times less than Serial output, both for 10 and 2.5.
Did anyone find the same thing?
I used an Arduino UNO for both outputs. My code follows:
#define SSRxPin 4

#define SSTxPin 3
#define PIN10 6
#define PIN25 5
#define PAYLOAD_LEN 8
#include <SoftwareSerial.h> // comunicazione con Feather
SoftwareSerial mySerial(SSRxPin, SSTxPin); //RX, TX verso ARduino
byte received[PAYLOAD_LEN];
byte i = 0;
byte ch = ' ';
byte flag = 0;
float PM10 = 0;
float PM25 = 0;
float TimePassed = 0;
float TimeOld = 0;
float Periodo = 10000;

void setup() {
pinMode(SSTxPin, OUTPUT);
pinMode(SSRxPin, INPUT);
while(!mySerial);
mySerial.begin(9600);
delay(1000);
while(!Serial);
Serial.begin(115200); // non minore di questa altrimenti si disincronizza
delay(1000);
Serial.println(" ProvaSDS011_Serial_PWM.ino");
}

void loop() {
if(mySerial.available() > 0){
ch = mySerial.read();
Serial.print(ch,HEX);Serial.print(" ");
if(flag){
received[i] = ch;
i++;
}
if(ch == 0xAA && !flag){
flag = 1;
i = 0;
}
if(ch == 0xAB && flag){
flag = 0;
Serial.println();
for(i = 0;i < PAYLOAD_LEN; i++){
Serial.print(received[i]);Serial.print(" ");
}
Serial.println();
int check = received[1]+received[2]+received[3]+received[4]+received[5]+received[6];
check = check % 256;
if(check != received[7]){
Serial.println(" ERRORE ");
}
Serial.print(" check ");Serial.println(check);
PM25 = float(received[2])*256.0 + float(received[1])/10.0;
PM10 = float(received[4])*256.0 + float(received[3])/10.0;
Serial.print(" PM10 ");Serial.print(PM10,1); Serial.print(" PM25 ");Serial.println(PM25,1);
}
}
TimePassed = millis()-TimeOld;
if(TimePassed > Periodo){
unsigned long durata1 = pulseIn(PIN10,HIGH,150000000);
// delay(5000);
unsigned long durata2 = pulseIn(PIN25,HIGH,150000000);
float Conc10 = float(durata1)/1000.0 - 2; //Conc in ug/m3
float Conc25 = float(durata2)/1000.0 - 2; //Conc in ug/m3
if(Conc10 < 0)Conc10 = 0;
if(Conc25 < 0)Conc25 = 0;
Serial.print(" ");Serial.print(durata1);Serial.print(" Conc10 ");
Serial.print(Conc10,1);Serial.print(" ");
Serial.print(durata2);Serial.print(" Conc25 ");Serial.print(Conc25,1);Serial.println();
TimeOld = millis();
}
}

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Read PWM on SDS011 Nova Fitness

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