ESP32 and MQ-135 working together, BUT NOT working with other sensors

[bossumoco]

/*************************************************************
ESP32 + MQ-135 + DHT22
 *************************************************************/

/* Fill-in information from Blynk Device Info here */
#define BLYNK_TEMPLATE_ID           ""
#define BLYNK_TEMPLATE_NAME         ""
#define BLYNK_AUTH_TOKEN            ""

/* Comment this out to disable prints and save space */
#define BLYNK_PRINT Serial


#include <WiFi.h>
#include <WiFiClient.h>
#include <BlynkSimpleEsp32.h>

// DHT22
#include "DHT.h"
#define DHTPIN 4     // Pin-ul digital conectat la DHT22
const int mq135Pin = 0;
#define DHTTYPE DHT22
#define REPORTING_PERIOD_MS 1000

// Your WiFi credentials.
// Set password to "" for open networks.
char ssid[] = "";
char pass[] = "";

BlynkTimer timer;

// Initializare DHT22
DHT dht(DHTPIN, DHTTYPE);
// Variabila delays
uint32_t tsLastReport = 0;



// This function is called every time the Virtual Pin 0 state changes
BLYNK_WRITE(V0)
{
  // Set incoming value from pin V0 to a variable
  int value = param.asInt();

  // Update state
  Blynk.virtualWrite(V1, value);
}

// This function is called every time the device is connected to the Blynk.Cloud
BLYNK_CONNECTED()
{
  // Change Web Link Button message to "Congratulations!"
  Blynk.setProperty(V3, "offImageUrl", "https://static-image.nyc3.cdn.digitaloceanspaces.com/general/fte/congratulations.png");
  Blynk.setProperty(V3, "onImageUrl",  "https://static-image.nyc3.cdn.digitaloceanspaces.com/general/fte/congratulations_pressed.png");
  Blynk.setProperty(V3, "url", "https://docs.blynk.io/en/getting-started/what-do-i-need-to-blynk/how-quickstart-device-was-made");
}

// This function sends Arduino's uptime every second to Virtual Pin 2.
void myTimerEvent()
{
  // You can send any value at any time.
  // Please don't send more that 10 values per second.
  Blynk.virtualWrite(V2, millis() / 1000);
  if (millis() - tsLastReport > REPORTING_PERIOD_MS)
  {
    // Reading temperature or humidity takes about 250 milliseconds!
    // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
    float h = dht.readHumidity();
    // Read temperature as Celsius (the default)
    float t = dht.readTemperature();
    if (isnan(h) || isnan(t)) {
      Serial.println(F("Failed to read from DHT sensor!"));
      return;
    }
    // Compute heat index in Celsius (isFahreheit = false)
    float hic = dht.computeHeatIndex(t, h, false);
    Blynk.virtualWrite(V4, h);
    Blynk.virtualWrite(V5, t);
    Blynk.virtualWrite(V6, hic);
    int sensorValue = analogRead(mq135Pin); // Pin 0 used 
    Serial.println(sensorValue); // Reading ONLY value of 0
    tsLastReport = millis();
  }
}

void setup()
{
  // Debug console
  Serial.begin(115200);

  Blynk.begin(BLYNK_AUTH_TOKEN, ssid, pass);
  // You can also specify server:
  //Blynk.begin(BLYNK_AUTH_TOKEN, ssid, pass, "blynk.cloud", 80);
  //Blynk.begin(BLYNK_AUTH_TOKEN, ssid, pass, IPAddress(192,168,1,100), 8080);

  // Setup a function to be called every second
  timer.setInterval(1000L, myTimerEvent);
  dht.begin();
}

void loop()
{
  Blynk.run();
  timer.run();

  // You can inject your own code or combine it with other sketches.
  // Check other examples on how to communicate with Blynk. Remember
  // to avoid delay() function!
}

This is working!

// Define the analog pin connected to the MQ-135 sensor
const int mq135Pin = 0;
uint32_t tsLastReport = 0;

#define REPORTING_PERIOD_MS 1000
void setup() {
  // Start the serial communication
  Serial.begin(115200);
}

void loop() {
if (millis() - tsLastReport > REPORTING_PERIOD_MS)
  {
    int sensorValue = analogRead(mq135Pin);
    Serial.println(sensorValue);
    tsLastReport = millis();
  }
}

(There's no point in sending it to Blynk if there is no value)

First code serial output:

Second code serial output:

Also the range of values change for every pin taken. As of now, with the 1st code which is displaying 0 values and 2nd working code, the voltage between literal PIN0 and GND is the same ~2.7V. I have to mention that I connected 1KOhm resistor between AO of MQ-135 and PIN0 (such that it takes no damage, because these ESP32 pins operate at 3.3V - that's what I remember I read.)

I also mention that I've disconnected my LCD which could be a power drainer.

Any advices?

[bossumoco]

Well apparently it doesn't work with Blynk. So it works with Blynk.begin() deleted. Does the ESP32 draw too much power for WiFi capabalities? Interestingly enough it works with DHT22.

[StefanL38]

if you suspect a power-supply-issue did you measure how much current your sensor is drawing?

Some USB-wires have really really thin copperwires which might lead to a significant voltage-drop.
I had differencies in the charge-current for smartphones between 0,3A with a bad cable and 1,2A with a very good cable.

The ESP's are known for short but high current-spikes. A big capacitor (2200 µF) at nearest possible position to Vin and GND and another one nearest to 3.3V and GND can help.

The onboard voltage-regulator has a limited current.
I would add serial printing starting right at

void setup() {
  Serial.begin();
  Serial.println("setup-Start");

to see if the "not working happends at void setup() or somehwhere below

best regards Stefan

[bossumoco]

Hello, I have been working on this and found the problem. In the initial post the mq135Pin was connected to the 0 PIN of the ESP32. After some research I've found code that worked where the Pin was 32. I don't know exactly why it's behaving like this.

This is the code that works with an ESP32, MQ-135, DHT22, a fan module (INB,INA,VCC,GND), a piezoBuzzer module (high trigger) and Blynk.

#define BLYNK_TEMPLATE_ID           "TMPLxxxxx"
#define BLYNK_TEMPLATE_NAME         "Quickstart Template"
#define BLYNK_AUTH_TOKEN            "Q-xxxx"

#define BLYNK_PRINT Serial
#include <WiFi.h>
#include <WiFiClient.h>
#include <BlynkSimpleEsp32.h>

#include <DHT.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

int lcdColumns = 16;
int lcdRows = 2;

byte degree_symbol[8] =
{
  0b00111,
  0b00101,
  0b00111,
  0b00000,
  0b00000,
  0b00000,
  0b00000,
  0b00000
};

char auth[] = BLYNK_AUTH_TOKEN;

char ssid[] = "xxxx";  // type your wifi name
char pass[] = "xxxx";  // type your wifi password

BlynkTimer timer;

#define REPORT_TIME 1000
int mq135Pin = 32;
int sensorThreshold = 100;
const int buzzerPin = 14;  // Pin 14 as the buzzer output
uint32_t tsLastReport = 0;

#define DHTPIN 4 //Connect Out pin to D2 in NODE MCU
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

int A1A = 12;
int A1B = 13;

void sendSensor()
{
  float h = dht.readHumidity();
  float t = dht.readTemperature(); // or dht.readTemperature(true) for Fahrenheit


  if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }
  int analogSensor = analogRead(mq135Pin);
  Blynk.virtualWrite(V7, analogSensor);
  Serial.print("mq135Pin Value: ");
  Serial.println(analogSensor);
  // You can send any value at any time.
  // Please don't send more that 10 values per second.
  Blynk.virtualWrite(V4, h);
  Blynk.virtualWrite(V5, t);
  float hic = dht.computeHeatIndex(t, h, false);
  Blynk.virtualWrite(V6, hic);

  Serial.print("Temperature : ");
  Serial.print(t);
  Serial.print("    Humidity : ");
  Serial.println(h);


}
void setup()
{
  pinMode(A1A, OUTPUT);
  pinMode(A1B, OUTPUT);

  pinMode(buzzerPin, OUTPUT);
  Serial.begin(115200);

  //pinMode(mq135Pin, INPUT);
  Blynk.begin(auth, ssid, pass);
  dht.begin();
  timer.setInterval(7000L, sendSensor);
  lcd.init();
  // turn on LCD backlight
  lcd.backlight();


  //  lcd.backlight();
  // lcd.clear();
  lcd.setCursor(3, 0);
  lcd.print("Monitorizare");
  lcd.setCursor(3, 1);
  lcd.print("Calitate Aer");
  delay(2000);
  lcd.clear();

  byte smiley[8] = {
    B00000,
    B10001,
    B00000,
    B00000,
    B10001,
    B01110,
    B00000,
  };

  byte sadFace[8] = {
    B00000,
    B10001,
    B00000,
    B00000,
    B01110,
    B10001,
    B00000,
  };

  // Load custom characters into LCD memory
  lcd.createChar(0, smiley);
  lcd.createChar(1, sadFace);
}

void loop()
{
  Blynk.run();
  timer.run();

  float h = dht.readHumidity();
  float t = dht.readTemperature(); // or dht.readTemperature(true) for Fahrenheit
  int analogSensor = analogRead(mq135Pin);

  if (t > 25)
  {

    digitalWrite(buzzerPin, HIGH);
    digitalWrite(A1A, HIGH);
    digitalWrite(A1B, LOW);

  } else if (t <= 25)
  {
    digitalWrite(buzzerPin, LOW);
    digitalWrite(A1A, LOW);
    digitalWrite(A1B, LOW);
  }

  float hic = dht.computeHeatIndex(t, h, false);


  // set cursor to first column, first row
  lcd.setCursor(0, 0);
  lcd.print(F("Temp: "));
  lcd.print(t);
  lcd.print((char)223);
  lcd.print("C");
  lcd.setCursor(0, 1);
  lcd.print(F("Hum: "));
  lcd.print(h);
  lcd.print(F("% "));
  lcd.write(0);
  delay(4000);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(F("Index C: "));
  lcd.print(hic);
  lcd.print((char)223);
  lcd.print("C");
  delay(4000);
  lcd.clear();
  lcd.setCursor(0, 1);
  lcd.print(F("Air Q: "));
  lcd.print(analogSensor);
  lcd.print(" ppm");
  delay(4000);
  lcd.clear();
}

I haven't come to the final behaviour of the system which requires just some more conditions put in the code that takes into account the mq135 value for some triggering events. I know it is recommended to avoid delays in the code, but this way I have my parameters uploaded onto cloud with no problem as of now. Maybe I will use something like

uint32_t tsLastReport = 0; // global var
// and in loop()
if(tsLastreport - millis() > REPORTING_TIME)
{
//output readings or calculate them or IDK
 tsLastReport = millis();
}

Thanks for your answer Stefan.

Good luck, everyone!