DHT11 | 3l3c7r1c pl4y6r0und

Having my first results in hand I have to modify my software a bit. The DHT11 sometimes give strange measuring values (0°C, 6°C) and I want to change my measuring procedure. I will measure 3 values for temperature and humidity and I will take the middle values. The soil moisture measurement is quite unstable so I will take the average of three measurements.

Additionally I have cleaned up the code structure.

I had troubles with two issues:

My measurement values are stored in arrays of struct. I learned that the typedef must be done in a header.
The ESP8266 does not support the std library. So I use a macro for the min function

That’s the result:

// Struct for measuring values
typedef struct {
 float temp;
 float hum;
 float soil;
} value_type;

// Struct for measuring values

typedef struct {

float temp;

float hum;

float soil;

} value_type;

#include 
#include "Logger.h"

// min macro for ESP
#define espmin(X, Y) (((X)<(Y))?(X):(Y))

// WiFi connection
const char* ssid = "SSID";
const char* password = "PASSWORD";
char server[] = "SERVERIP";
int port = 80;
WiFiClient client;
const unsigned long postingInterval = 1800L * 1000000L; // delay between updates, in microseconds

//DHT 
#include 
#define DHTPIN 4
#define DHTTYPE DHT11   // DHT 11 
DHT dht(DHTPIN, DHTTYPE,16);

// needed to avoid link error on ram check
extern "C" 
{
#include "user_interface.h"
}

void setup() {
  value_type values[3];
  // start serial
  pinMode(12, OUTPUT);
  pinMode(A0, INPUT);
  dht.begin();

  Serial.begin(115200);
  Serial.println("WLAN Greenhouse Data Logger - Electric Playground");
  
  // First measuring
  values[0]= domeasuring();
  delay(1000);
  // Second measuring
  values[1]= domeasuring();
  delay(1000);
  // Third measuring
  values[2]= domeasuring();
  
  // Finding the middle value
  float temp;
  float hum;
  float minmin = espmin(espmin(values[0].temp, values[1].temp), values[2].temp);
  if (values[0].temp = minmin)
  {
    temp=espmin(values[1].temp, values[2].temp);
    hum=espmin(values[1].hum, values[2].hum);
  }
  else if (values[1].temp = minmin)
  {
    temp=espmin(values[0].temp, values[2].temp);
    hum=espmin(values[0].hum, values[2].hum);
  }
  else
  {
    temp=espmin(values[0].temp, values[1].temp);
    hum=espmin(values[0].hum, values[1].hum);
  }
  float soil=(values[0].soil+values[1].soil+values[1].soil)/3.0;

  // send data

  // Connect to WIFI
  WiFi.mode(WIFI_STA);
  WiFiStart();

  // debug
  while (client.available()) {
    char c = client.read();
    Serial.write(c);
  }
  
  Serial.println("Humidity:"+String(hum,2)+"\tTemperature:"+String(temp,2)+"\tSoil:"+String(soil,2));
  httpRequest(hum,temp,soil);
  Serial.println("Good Night");
  ESP.deepSleep(postingInterval, WAKE_NO_RFCAL); //WAKE_DEFAULT, WAKE_RFCAL, WAKE_NO_RFCAL, WAKE_RF_DISABLED.
  delay(1000);
}

void loop() {
 // do nothing
}

// Measueing
value_type domeasuring() {
  digitalWrite(12, HIGH);
  delay(300);
  value_type retval;
  retval.hum = dht.readHumidity();
  if (isnan(retval.hum))
    retval.hum=999;
  
  retval.temp = dht.readTemperature();
  if (isnan(retval.temp))
    retval.temp=999;
    
  retval.soil = analogRead(A0);
  digitalWrite(12, LOW);
  Serial.println("Humidity:"+String(retval.hum,2)+"\tTemperature:"+String(retval.temp,2)+"\tSoil:"+String(retval.soil,2));
  return retval;
}

void httpRequest(float h, float t, float s) {
  // close any connection before send a new request.
  // This will free the socket on the WiFi shield
  client.stop();
  delay(100);
  // We now create a URI for the request
  String url = "/newrecord.php?";
  url += "temp=";
  url += String(t,2);
  url += "&humidity=";
  url += String(h,2);
  url += "&soil=";
  url += String(s,2);
  // if there's a successful connection:
  if (client.connect(server, port)) {
    Serial.println("connecting...");
    client.print(String("GET ") + url + " HTTP/1.1\r\n" +
               "Host: " + server + "\r\n" + 
               "Connection: close\r\n\r\n");
    Serial.println("data submitted.");
    delay(10);
  
  } else {
    // if you couldn't make a connection:
    Serial.println("connection failed");
  }
}

void WiFiStart()
{ 
  // Connect to WiFi network
  Serial.print("Connecting to ");
  Serial.println(ssid);

  
  WiFi.begin(ssid, password);
  
  while (WiFi.status() != WL_CONNECTED) 
  {
    delay(250);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected");
  // Print the IP address
  Serial.println(WiFi.localIP());
}

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#include

#include "Logger.h"

// min macro for ESP

#define espmin(X, Y) (((X)<(Y))?(X):(Y))

// WiFi connection

const char* ssid = "SSID";

const char* password = "PASSWORD";

char server[] = "SERVERIP";

int port = 80;

WiFiClient client;

const unsigned long postingInterval = 1800L * 1000000L; // delay between updates, in microseconds

//DHT

#include

#define DHTPIN 4

#define DHTTYPE DHT11 // DHT 11

DHT dht(DHTPIN, DHTTYPE,16);

// needed to avoid link error on ram check

extern "C"

{

#include "user_interface.h"

}

void setup() {

value_type values[3];

// start serial

pinMode(12, OUTPUT);

pinMode(A0, INPUT);

dht.begin();

Serial.begin(115200);

Serial.println("WLAN Greenhouse Data Logger - Electric Playground");

// First measuring

values[0]= domeasuring();

delay(1000);

// Second measuring

values[1]= domeasuring();

delay(1000);

// Third measuring

values[2]= domeasuring();

// Finding the middle value

float temp;

float hum;

float minmin = espmin(espmin(values[0].temp, values[1].temp), values[2].temp);

if (values[0].temp = minmin)

{

temp=espmin(values[1].temp, values[2].temp);

hum=espmin(values[1].hum, values[2].hum);

}

else if (values[1].temp = minmin)

{

temp=espmin(values[0].temp, values[2].temp);

hum=espmin(values[0].hum, values[2].hum);

}

else

{

temp=espmin(values[0].temp, values[1].temp);

hum=espmin(values[0].hum, values[1].hum);

}

float soil=(values[0].soil+values[1].soil+values[1].soil)/3.0;

// send data

// Connect to WIFI

WiFi.mode(WIFI_STA);

WiFiStart();

// debug

while (client.available()) {

char c = client.read();

Serial.write(c);

}

Serial.println("Humidity:"+String(hum,2)+"\tTemperature:"+String(temp,2)+"\tSoil:"+String(soil,2));

httpRequest(hum,temp,soil);

Serial.println("Good Night");

ESP.deepSleep(postingInterval, WAKE_NO_RFCAL); //WAKE_DEFAULT, WAKE_RFCAL, WAKE_NO_RFCAL, WAKE_RF_DISABLED.

delay(1000);

}

void loop() {

// do nothing

}

// Measueing

value_type domeasuring() {

digitalWrite(12, HIGH);

delay(300);

value_type retval;

retval.hum = dht.readHumidity();

if (isnan(retval.hum))

retval.hum=999;

retval.temp = dht.readTemperature();

if (isnan(retval.temp))

retval.temp=999;

retval.soil = analogRead(A0);

digitalWrite(12, LOW);

Serial.println("Humidity:"+String(retval.hum,2)+"\tTemperature:"+String(retval.temp,2)+"\tSoil:"+String(retval.soil,2));

return retval;

}

void httpRequest(float h, float t, float s) {

// close any connection before send a new request.

// This will free the socket on the WiFi shield

client.stop();

delay(100);

// We now create a URI for the request

String url = "/newrecord.php?";

url += "temp=";

url += String(t,2);

url += "&humidity=";

url += String(h,2);

url += "&soil=";

url += String(s,2);

// if there's a successful connection:

if (client.connect(server, port)) {

Serial.println("connecting...");

client.print(String("GET ") + url + " HTTP/1.1\r\n" +

"Host: " + server + "\r\n" +

"Connection: close\r\n\r\n");

Serial.println("data submitted.");

delay(10);

} else {

// if you couldn't make a connection:

Serial.println("connection failed");

}

void WiFiStart()

{

// Connect to WiFi network

Serial.print("Connecting to ");

Serial.println(ssid);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED)

{

delay(250);

Serial.print(".");

}

Serial.println("");

Serial.println("WiFi connected");

// Print the IP address

Serial.println(WiFi.localIP());

}

In a first step I will make a prototype for my sensor board. Usually you build a prototype just on a breadboard. But I would like to use my prototype for some weeks to see how my sensors work and how much energy is needed. Therefore I use a prototype circuit board instead.

My shopping list for that:

Additionally I need:

A prototype circuit board
3 pcs. 10k Resistors (can be even bigger as long aa all 3 are equal)
1 electrolytic capacitor (>500uF)
1 Transisotr (e.g. BC547C)
1 3K3 Resistor
a pin header
a jumper
a soldering iron

I know that there a many statements about the right soldering iron in the internet but for me personally a cheap soldering station is more than enough. There is also a good desoldering pump coming with the station and every beginner will need it. If you have too much money then spend it in a quite good solder. As power supply I use a USB powerbank that I’ve received as a giveaway. You can also get one for less than 10€ (e.g. here)

I try to do not solder items directly when building a prototype. Therefore I use pin headers. The disadvantage is that the prototype is not that robust but the advantage is I can easily borrow some parts without taking the soldering iron.

The ESP8266 just takes 3.3V so I take the USB to TTL converter also as voltage converter. Be sure to put the jumper to 3.3V. To safe energy I will put my ESP in deep-sleep. To prevent my sensors taking power when they are not used I use a transistor to power them on only when needed. The ESP needs quite a high current when connecting to the WLAN. I use an electrolytic capacitor parallel to the voltage supply. Sizing of that is no rocket science, it should be somewhere between 400uF and 2200uF (6-10V). For programming the ESP the CH_PD Pin has to be put on ground. Some recommend a button for that but I prefer a jumper.

The manual for the ESP8266 says that for wake up from deep-sleep pin 16 has to be connected to CH_PD. Unfortunately for some reasons this is not working with mine. I use the RESET for the wakeup instead. This prevents using some options for wakeup but I don’t care for the prototype.

Der Prototyp in EAGLE — Prototype in EAGLE

It is a puzzle to place all the components on the board. I tried to save as much space because I had a small leftover to be used.

Meine Prototyen Platine — My final prototype

For programming my ESP I use the Arduio IDE. You have to install the ESP board in the IDE. Add in File->Properties->Additional Board Manager URLs: http://arduino.esp8266.com/stable/package_esp8266com_index.json Select Board „…“ > Board Manager… , choose esp8266 and press install. After that you can program the ESP like any other Arduino. For programming the jumper has to be set on starting the board. Sometimes the upload fails with some strange error messages. If this happens I simply restart the ESP and try it again. Remember to remove the jumper after uploading the software. Wake-up from deep-sleep is not working when the jumper ist set.

#include 

// WLAN Name und Password (PSK)
const char* ssid = "SSID";
const char* password = "PSK"; 
WiFiClient client;

// Server Adress of my raspberry
char server[] = "10.0.0.3";
int port = 80; //If you use a different port on your webserver adjust the no here

// Update Intervall
const unsigned long postingInterval = 1800L * 1000000L;

//DHT init
#include 
#define DHTPIN 4
#define DHTTYPE DHT11   // DHT 11 
DHT dht(DHTPIN, DHTTYPE,16);

// needed to avoid link error on ram check
extern "C" 
{
#include "user_interface.h"
}

void setup() {
  // Pin 12 powers the sensors
  pinMode(12, OUTPUT);
  digitalWrite(12, HIGH);
  // Serial interface for debugging
  Serial.begin(115200);
  Serial.println("WLAN Logger - Electric Playground");
  // start WIFI
  WiFi.mode(WIFI_STA);
  WiFiStart();
  // waiting
  delay(3000);
  //DHT init
  dht.begin();
  // ADC (Soil) init
  pinMode(A0, INPUT);
}

void loop() {
  // debug
  while (client.available()) {
    char c = client.read();
    Serial.write(c);
  }
  // read sensor values
  float hum = dht.readHumidity();
  float temp = dht.readTemperature();
  float soil = analogRead(A0);
  //Debug
  Serial.println("Humidity:"+String(hum,2)+"\tTemperature:"+String(temp,2)+"\tSoil:"+String(soil,2));
  //Send values
  httpRequest(hum,temp,soil);
  //power of sensors and go to deep sleep
  delay(500);
  digitalWrite(12, LOW);
  ESP.deepSleep(postingInterval, WAKE_NO_RFCAL); 
  delay(1000);
}


//Transmit data to webserver
void httpRequest(float h, float t, float s) {
  client.stop();
  delay(100);
  //build URL
  String url = "/newrecord.php?";
  url += "temp=";
  url += String(t,2);
  url += "&humidity=";
  url += String(h,2);
  url += "&soil=";
  url += String(s,2);
  // call URL
  if (client.connect(server, port)) {
    Serial.println("connecting...");
    client.print(String("GET ") + url + " HTTP/1.1\r\n" +
               "Host: " + server + "\r\n" + 
               "Connection: close\r\n\r\n");
    Serial.println("data submitted.");
    delay(10);
  
  } else {
    Serial.println("connection failed");
  }
}
// Establish WIFI connection
void WiFiStart()
{ 
  Serial.print("Connecting to ");
  Serial.println(ssid); 
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) 
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println(WiFi.localIP());
}

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#include

// WLAN Name und Password (PSK)

const char* ssid = "SSID";

const char* password = "PSK";

WiFiClient client;

// Server Adress of my raspberry

char server[] = "10.0.0.3";

int port = 80; //If you use a different port on your webserver adjust the no here

// Update Intervall

const unsigned long postingInterval = 1800L * 1000000L;

//DHT init

#include

#define DHTPIN 4

#define DHTTYPE DHT11 // DHT 11

DHT dht(DHTPIN, DHTTYPE,16);

// needed to avoid link error on ram check

extern "C"

{

#include "user_interface.h"

}

void setup() {

// Pin 12 powers the sensors

pinMode(12, OUTPUT);

digitalWrite(12, HIGH);

// Serial interface for debugging

Serial.begin(115200);

Serial.println("WLAN Logger - Electric Playground");

// start WIFI

WiFi.mode(WIFI_STA);

WiFiStart();

// waiting

delay(3000);

//DHT init

dht.begin();

// ADC (Soil) init

pinMode(A0, INPUT);

}

void loop() {

// debug

while (client.available()) {

char c = client.read();

Serial.write(c);

}

// read sensor values

float hum = dht.readHumidity();

float temp = dht.readTemperature();

float soil = analogRead(A0);

//Debug

Serial.println("Humidity:"+String(hum,2)+"\tTemperature:"+String(temp,2)+"\tSoil:"+String(soil,2));

//Send values

httpRequest(hum,temp,soil);

//power of sensors and go to deep sleep

delay(500);

digitalWrite(12, LOW);

ESP.deepSleep(postingInterval, WAKE_NO_RFCAL);

delay(1000);

}

//Transmit data to webserver

void httpRequest(float h, float t, float s) {

client.stop();

delay(100);

//build URL

String url = "/newrecord.php?";

url += "temp=";

url += String(t,2);

url += "&humidity=";

url += String(h,2);

url += "&soil=";

url += String(s,2);

// call URL

if (client.connect(server, port)) {

Serial.println("connecting...");

client.print(String("GET ") + url + " HTTP/1.1\r\n" +

"Host: " + server + "\r\n" +

"Connection: close\r\n\r\n");

Serial.println("data submitted.");

delay(10);

} else {

Serial.println("connection failed");

}

// Establish WIFI connection

void WiFiStart()

{

Serial.print("Connecting to ");

Serial.println(ssid);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED)

{

delay(500);

Serial.print(".");

}

Serial.println("");

Serial.println("WiFi connected");

Serial.println(WiFi.localIP());

}

Category: DHT11

Irrigation – Part 5: Software Update

Irrigation- Part 1: A Prototype

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