John RanshawChristopher Ames
Published © GPL3+

Temperature and Humidity Sensor Controlling Humidifier

The use of a simple circuit and a DHT11 sensor to read the temperature and humidity. Allowing for the automated control of a humidifier.

IntermediateFull instructions provided7 hours313
Temperature and Humidity Sensor Controlling Humidifier

Things used in this project

Hardware components

Photon
Particle Photon
×2
DHT11 Temperature & Humidity Sensor (3 pins)
DHT11 Temperature & Humidity Sensor (3 pins)
×1
Operational Amplifier, Op Amp + Comparator + Reference
Operational Amplifier, Op Amp + Comparator + Reference
×1
Resistor 10k ohm
Resistor 10k ohm
×2
LED (generic)
LED (generic)
×2
Jumper wires (generic)
Jumper wires (generic)
×10
Micro-USB to USB Cable (Generic)
Micro-USB to USB Cable (Generic)
×2

Software apps and online services

Particle Build Web IDE
Particle Build Web IDE
ThingSpeak API
ThingSpeak API

Story

Read more

Schematics

The DHT11 Sensor Circuit

There was no DHT11 part available in the program so I used a different temperature sensor. However, I only used the three pins exactly how I would with the DHT11 that we used.

Humidifier Sensor Circuit

All of the wires going off of the breadboard are connected to our hand-made humidifier. These wires may vary for a different humidifier. The black node and the resistor between the photon and the op-amp is not needed for the completion of the project. It was an unneccesary add on.

Humidifier Sensor Circuit

This diagram shows the setup for the humidifier. To turn on the heater block, a PWM signal is sent to the relay on the breadboard which then switches the heats inked MOSFET.

Code

Working the DHT11 Sensor

C/C++
This code is used to gather the data of the DHT11 sensor and graph it. While sending to the other photon for use.
// This #include statement was automatically added by the Particle IDE.
#include <PietteTech_DHT.h>

#include "ThingSpeak.h"

#define DHTTYPE  DHT11      // Sensor type DHT11/21/22/AM2301/AM2302
#define DHTPIN   3          // Digital pin for communications


PietteTech_DHT DHT(DHTPIN, DHTTYPE);

int n=0;      // counter
int LEDpin=D6;
float h_set=90;

bool humid = false;

TCPClient client;


unsigned long myChannelNumber = 758578;
const char * myWriteAPIKey = "J9R2AAQEJK14M5W9";

void setup() {
  ThingSpeak.begin(client);
  
  Serial.begin(9600);
  pinMode (D3, INPUT);
  pinMode (LEDpin,OUTPUT);
  
  bool humid = false;
    
     Particle.publish("humiditysensorthreshold", "off");
     Particle.subscribe("heaterblockon", myHandler);
  
}

void loop() {
  int result = DHT.acquireAndWait(1000); // wait up to 1 sec (default indefinitely)

  switch (result) {
  case DHTLIB_OK:
    Serial.println("OK");
    break;
  case DHTLIB_ERROR_CHECKSUM:
    Serial.println("Error\n\r\tChecksum error");
    break;
  case DHTLIB_ERROR_ISR_TIMEOUT:
    Serial.println("Error\n\r\tISR time out error");
    break;
  case DHTLIB_ERROR_RESPONSE_TIMEOUT:
    Serial.println("Error\n\r\tResponse time out error");
    break;
  case DHTLIB_ERROR_DATA_TIMEOUT:
    Serial.println("Error\n\r\tData time out error");
    break;
  case DHTLIB_ERROR_ACQUIRING:
    Serial.println("Error\n\r\tAcquiring");
    break;
  case DHTLIB_ERROR_DELTA:
    Serial.println("Error\n\r\tDelta time to small");
    break;
  case DHTLIB_ERROR_NOTSTARTED:
    Serial.println("Error\n\r\tNot started");
    break;
  default:
    Serial.println("Unknown error");
    break;
  }

  n++;
  
int humidity = DHT.getHumidity();
int temperature = DHT.getFahrenheit();
  
if(DHT.getHumidity()<h_set){
        Particle.publish("humiditysensorthreshold", "on");
    }
    else {
        Particle.publish("humiditysensorthreshold", "off");
    }


  ThingSpeak.setField(1,humidity);
  ThingSpeak.setField(2,temperature);
  
  Serial.print(DHT.getHumidity());
Serial.println("h");
Serial.print(DHT.getFahrenheit());
Serial.println("t");

  
  ThingSpeak.writeFields(myChannelNumber, myWriteAPIKey);  

  delay(15000); // ThingSpeak will only accept updates every 15 seconds. 
}

void myHandler(String event, String data)
{
    if(data == "on"){
        digitalWrite(LEDpin,HIGH);}
     if(data == "off"){
        digitalWrite(LEDpin,LOW);}
}

Working the Humidifer

C/C++
This code is used to start and stop the humidifier based on the data received from the other photon.
#include <math.h>
int ThermistorPin = A0;
int PWM_Pin = D3;
int LEDpin= D5;

int EState;
int ELastState;
int counter=0;

int Resistor1 = 10000;
int B=3950;// thermistor beta coefficient
int samples[8];
int i;
float Therm_resistance;
double T;
float Vout;

float kp = 6;   
float ki = 0.5;   
float PID_p=0;    float PID_i=0;
float PID_error=0;
float PID_value=0;

int set_temperature = 220;

float previous_error;
float elapsedTime, timePrev;

void setup() {
    Particle.publish("heaterblockon", "off");
    Particle.subscribe("humiditysensorthreshold", myHandler);
Serial.begin(9600);

pinMode (PWM_Pin, OUTPUT);
pinMode (ThermistorPin,INPUT);
pinMode (LEDpin, OUTPUT);
digitalWrite(LEDpin,LOW);

  
}

void loop() {

  Vout = analogRead(ThermistorPin);
 for (i=0; i< 8; i++) {
   samples[i] = analogRead(ThermistorPin);
   delay(10);
  }
 
  // average all the samples out
  Vout = 0;
  for (i=0; i< 8; i++) {
     Vout += samples[i];
  }
  Vout /= 8;

  //To find thermistor resistance
  Therm_resistance = Resistor1 / (4095/Vout-1);
  //Steinhart_Hart equation, ouputs in kelvin
  T = (1/(((log(Therm_resistance / 10000))/B)+(1.0 / (25 + 273.15))));
  //convert to celcius
  T = T - 273.15;
  //convert to farenheit
  T = (T * 9.0)/ 5.0 + 32.0; 
 
  //calculate the error
  PID_error = set_temperature - T;

//calculations needed for PID_p
   PID_p=PID_error;
  
  //Calculate the I value 
    PID_i += (PID_error);
    if (PID_i>50){
      PID_i=50;
    }
    if (PID_i<-50){
      PID_i=-50;
    }
    else{
     PID_i=PID_i;
    }
     
  //Final total PID value 
  PID_value = (PID_p*kp) + (PID_i*ki);
  
  //PWM range between 0 and 255 (0-100 duty cycle)
  if(PID_value < 0)
  {    PID_value = 0;    }
  if(PID_value > 255)  
  {    PID_value = 255;  }
  else PID_value=PID_value;
 
  {analogWrite(PWM_Pin,PID_value);  
  //digitalWrite(LEDpin, HIGH);}
  }
    previous_error = PID_error;
    
    Serial.print(PID_value);
Serial.println("pid");
Serial.print(set_temperature);
Serial.println("tset");
Serial.print(PID_i);
Serial.println("i");
Serial.print(set_temperature);
Serial.println("t");

  
  delay(1000);
}

void myHandler(String event, String data)
{
    if(data == "on"){
    Particle.publish("heaterblockon", "on");
        set_temperature=220;
        digitalWrite(LEDpin,HIGH);}
     if(data == "off"){
        Particle.publish("heaterblockon", "off");
        set_temperature=0;
        digitalWrite(LEDpin,LOW);}
}

Credits

John Ranshaw

John Ranshaw

1 project • 0 followers
Christopher Ames

Christopher Ames

1 project • 0 followers

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