DHT11 Dew Point and Delay

Projects Programming
1

I've gone down the Arduino rabbit hole, I spend all my time on this thing.
I'm building a box that controls humidity and temperature with a DHT11 sensor.

I have been trying to add dew point to my setup but not getting anywhere, is there a simple way to add it to my code?

I also have been working on how to make the code change after a few days, the same code for 4 days, then change the humidity and temp settings?

#include <SimpleDHT.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
dht DHT;

int pinDHT11 = 2;   // Declaring digital pin no 2 as the dht11  data pin
int DHTpower = 3;  // Power for DHT11
int intakefan = 4; //  Intake fan for Humid box and dry 
int humidv = 5;     //  Valve for humud intake
int dryv = 6; // dry box valve
int exfan = 7;  // exhaust fan
int exv = 8;  // exhaust valve
int returnfan = 9; // fan to bring air from inside box
int returnv = 10; //  return valve, air from inside box
SimpleDHT11  dht11;  
LiquidCrystal_I2C lcd(0x27, 16, 2); // Set the LCD address to 0x27 for a 16x2 display

void setup() {
  pinMode(intakefan, OUTPUT);
  pinMode(humidv, OUTPUT);
  pinMode(dryv, OUTPUT);
  pinMode(exfan, OUTPUT);
  pinMode(exv, OUTPUT);
  pinMode(returnfan, OUTPUT);
  pinMode(returnv, OUTPUT);
  pinMode(DHTpower, OUTPUT);
  digitalWrite(intakefan, LOW);
  digitalWrite(humidv, LOW);
  digitalWrite(dryv, LOW);
  digitalWrite(exfan, LOW);
  digitalWrite(exv, LOW);
  digitalWrite(returnfan, LOW);
  digitalWrite(returnv, LOW);
  digitalWrite(DHTpower, LOW);
  Serial.begin(9600);   
  lcd.init();      // Initialize the LCD
  lcd.backlight(); // Turn on the backlight
  lcd.clear();     // Clear the LCD screen
  lcd.setCursor(3, 0);
  lcd.print("Welcome");

}


void loop() {
{
  int chk = DHT.read11(DHT11_PIN);
  Serial.print("Temperature = ");
  Serial.print(DHT.temperature);
  Serial.print("*C");
  Serial.println();
  Serial.print("Humidity = ");
  Serial.print(DHT.humidity);
  Serial.print("%");
  Serial.println();
  double gamma = log(DHT.humidity / 100) + ((17.62 * DHT.temperature) / (243.5 + DHT.temperature));
  double dp = 243.5 * gamma / (17.62 - gamma);

  Serial.print("Dew point = ");
  Serial.print(dp);
  Serial.print(" *Celcius ");
  Serial.println();
  delay(3000);
}



void  RHcheck() {                    //Check Humidity Level Function
  digitalWrite(DHTpower,  HIGH);     //On Humidity Sensor
  delay(50);
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Checking");
  lcd.setCursor(0,1);
  lcd.print("Humidity");


   
  byte temperature = 0;
  byte humidity = 0;
  int  err = SimpleDHTErrSuccess;

  //This bit will tell our Arduino what to do  if there is some sort of an error at getting readings from our sensor
  if ((err  = dht11.read(pinDHT11, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
    Serial.print("No reading , err="); Serial.println(err);delay(100);
    
  }
 
  if (((int)humidity > 60) && ((int)humidity < 65))  {     // Ok Humidity - Do nothing
    digitalWrite(intakefan, LOW);
    digitalWrite(humidv, LOW);
    digitalWrite(dryv, LOW);
    digitalWrite(exfan, LOW);
    digitalWrite(exv, LOW);
    digitalWrite(DHTpower, LOW);
    digitalWrite(returnfan, LOW);
    digitalWrite(returnv, LOW);
    lcd.clear();
    lcd.print("Fans OFF");
    lcd.setCursor(0,1);
    lcd.print("Valves Closed");
    delay(1500);
    lcd.clear();
    lcd.print((int)humidity); lcd.print(" % Humidity");
    lcd.setCursor(0,1);
    lcd.print((int)temperature); lcd.print(" Celcius");


  }if ((int)humidity < 55 ){

    digitalWrite(humidv, HIGH);
    digitalWrite(dryv, LOW);
    digitalWrite(exv, HIGH);
    digitalWrite(DHTpower, LOW);
    digitalWrite(returnfan, LOW);
    digitalWrite(returnv, LOW);
    delay(3000);
    digitalWrite(intakefan, HIGH);
    digitalWrite(exfan, HIGH);
    lcd.clear();
    lcd.print("Fans On");
    lcd.setCursor(0,1);
    lcd.print("Humid Box");
    delay(1000);
    lcd.clear();
    lcd.print((int)humidity); lcd.print(" % Humidity");
    lcd.setCursor(0,1);
    lcd.print((int)temperature); lcd.print(" Celcius");

  }if((int)humidity > 70 ){
    
    digitalWrite(humidv, LOW);
    digitalWrite(dryv, HIGH);
    digitalWrite(exv, HIGH);
    digitalWrite(DHTpower, LOW);
    digitalWrite(returnv, HIGH);
    digitalWrite(exfan, HIGH);
    delay(3000);
    digitalWrite(intakefan, HIGH);
    digitalWrite(returnfan, HIGH);
    lcd.clear();
    lcd.print("Fans On");
    lcd.setCursor(0,1);
    lcd.print("Dry Box");
    delay(1000);
    lcd.clear();
    lcd.print((int)humidity); lcd.print(" % Humidity");
    lcd.setCursor(0,1);
    lcd.print((int)temperature); lcd.print(" Celcius");
  
  }
}
3

Well I stuck together some code from other places and im getting there.

How do you use the "dew point" in an IF statement to set pins high?

#include <LiquidCrystal_I2C.h>


//
double dewPoint(double celsius, double humidity) {
  // (1) Saturation Vapor Pressure = ESGG(T)
  double RATIO = 373.15 / (273.15 + celsius);
  double RHS = -7.90298 * (RATIO - 1);
  RHS += 5.02808 * log10(RATIO);
  RHS += -1.3816e-7 * (pow(10, (11.344 * (1 - 1 / RATIO))) - 1);
  RHS += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1);
  RHS += log10(1013.246);

  // factor -3 is to adjust units - Vapor Pressure SVP * humidity
  double VP = pow(10, RHS - 3) * humidity;

  // (2) DEWPOINT = F(Vapor Pressure)
  double T = log(VP / 0.61078);  // temp var
  return (241.88 * T) / (17.558 - T);
}

// Example testing sketch for various DHT humidity/temperature sensors
// Written by ladyada, public domain

#include "DHT.h"

#define DHTPIN 7  // what pin we're connected to

// Uncomment whatever type you're using!
#define DHTTYPE DHT11  // DHT 11
//#define DHTTYPE DHT22 // DHT 22 (AM2302)
//#define DHTTYPE DHT21 // DHT 21 (AM2301)

// Connect pin 1 (on the left) of the sensor to +5V
// NOTE: If using a board with 3.3V logic like an Arduino Due connect pin 1
// to 3.3V instead of 5V!
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

// Initialize DHT sensor for normal 16mhz Arduino
DHT dht(DHTPIN, DHTTYPE);
// NOTE: For working with a faster chip, like an Arduino Due or Teensy, you
// might need to increase the threshold for cycle counts considered a 1 or 0.
// You can do this by passing a 3rd parameter for this threshold. It's a bit
// of fiddling to find the right value, but in general the faster the CPU the
// higher the value. The default for a 16mhz AVR is a value of 6. For an
// Arduino Due that runs at 84mhz a value of 30 works.
// Example to initialize DHT sensor for Arduino Due:
//DHT dht(DHTPIN, DHTTYPE, 30);

int intakefan = 4;  //  Intake fan for Humid box and dry box
int humidv = 5;     //  Valve for humud intake
int dryv = 6;       // dry box valve
int exfan = 7;      // exhaust fan
int exv = 8;        // exhaust valve
int returnfan = 9;  // fan to bring air from inside box
int returnv = 10;   //  return valve, air from inside box

LiquidCrystal_I2C lcd(0x27, 16, 2);  // Set the LCD address to 0x27 for a 16x2 display
void setup() {
  pinMode(intakefan, OUTPUT);
  pinMode(humidv, OUTPUT);
  pinMode(dryv, OUTPUT);
  pinMode(exfan, OUTPUT);
  pinMode(exv, OUTPUT);
  pinMode(returnfan, OUTPUT);
  pinMode(returnv, OUTPUT);

  digitalWrite(intakefan, LOW);
  digitalWrite(humidv, LOW);
  digitalWrite(dryv, LOW);
  digitalWrite(exfan, LOW);
  digitalWrite(exv, LOW);
  digitalWrite(returnfan, LOW);
  digitalWrite(returnv, LOW);

  Serial.begin(9600);
  lcd.init();       // Initialize the LCD
  lcd.backlight();  // Turn on the backlight
  lcd.clear();      // Clear the LCD screen
  lcd.setCursor(3, 0);
  lcd.print("The Green");
  lcd.setCursor(4, 1);
  lcd.print("Ninja");
  delay(2000);  // Display the startup message for 2 seconds
  lcd.clear();  // Clear the LCD screen
  dht.begin();
}

void loop() {
  // Wait a few seconds between measurements.
  delay(2000);

  // 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
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit
  float f = dht.readTemperature(true);

  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Compute heat index
  // Must send in temp in Fahrenheit!
  float hi = dht.computeHeatIndex(f, h);
  float hiDegC = dht.convertFtoC(hi);


  delay(50);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Checking");
  lcd.setCursor(0, 1);
  lcd.print("Humidity");
  Serial.print(f);
  Serial.print(" *F\t");
  Serial.print("Heat index: ");
  Serial.print(hiDegC);
  Serial.print(" *C ");
  Serial.print(hi);
  Serial.print(" *F ");
  Serial.print("Dew Point (*C): ");
  Serial.println(dewPoint(t, h));
}
4

Start by getting the dewpoint into a variable

float currentDew = dewPoint(t, h);

Then you can test the value of the variable

if (currentDew < 123)
{
  Serial.println("dewpoint is lower than 123");
}
else
{
  Serial.println("dewpoint is 123 or greater");
}

Replace the prints with the actions that you want to take and the value against which the dewpoint is tested to the value that you want

5

Try this link, it has a lot of information that will help you: Dew Point Formula, Dew Point Temperature Chart (+ Calculator) - LearnMetrics

6

Thank you sir, I was so close :smiley:

7

Thats awesome, thank you

8

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