Wireless Temperature and Humidity Measurement with Arduino LCD Display

Using Arduino Programming Questions
1

Hi for all,
I need advice about my intention to create one sender (DHT11, NRF24L01 and UNO) and one receiver (NRF24L01 and UNO, 16x2 LCD). I test via serial monitor, sender says data can not sent but it can measure the temperature and humidity. I have a problem about LCD i guess, but when i tried to write hello world it works. Here is my codes. Please check. My LCD display photos are attached. I double checked my codes, solders and connections. They're all OK. What's wrong about my project? I guess it could be about something missing in my code.

#include <SPI.h>
#include <nRF24L01p.h>
#include <String.h>
#include <dht11.h>
#define DHT11PIN A0

dht11 DHT11;

nRF24L01p transmitter(9,10);
/* CSN - > 10, CE -> 9 defined */

float temp_variable;
float hum_variable;

static char temp[10];
static char hum[10];

void setup() {
  Serial.begin(9600);
  SPI.begin();
  SPI.setBitOrder(MSBFIRST);
  /* SPI initialize */
  transmitter.channel(80);
  transmitter.TXaddress("0xe7e7e7e7e7");
  transmitter.init();
  /* Transmitter settings done */
}
void loop() {
  int chk = DHT11.read(DHT11PIN);

  temp_variable = (float)DHT11.temperature;
  hum_variable      = (float)DHT11.humidity;
  
  Serial.print("Nem (%): ");
  Serial.println(hum_variable, 2);

  Serial.print("Sicaklik (Celcius): ");
  Serial.println(temp_variable, 2);
  
  dtostrf(hum_variable,5, 2, hum);
  
  dtostrf(temp_variable,5, 2, temp);
  /* float value converted to string value for temperature */
  
  transmitter.txPL(temp);
  transmitter.txPL(hum);
  boolean sendstate = transmitter.send(FAST);
  /* Temperature information transmitted to nRF24L01 */
  /* If there is a failure, sendstate's value will be false */
  if(sendstate==true){
        Serial.println("Data sent successfully");
  }else{
        Serial.println("Data can not sent!");
  }  
  delay(1000); 
}

#include <SPI.h>
#include <nRF24L01p.h>
#include <LiquidCrystal.h>
#include "printf.h"
#include <stdlib.h>
#include <stdio.h>      /* printf, NULL */

LiquidCrystal lcd(10, 9, 5, 4, 3, 2);

nRF24L01p receiver(7,8);
/* CSN - > 7, CE -> 8 defined */

void setup(){
  Serial.begin(9600);
  lcd.begin(16, 2);
    
  SPI.begin();
  SPI.setBitOrder(MSBFIRST);
  /* SPI initialized */
  receiver.channel(80);
  receiver.RXaddress("0xe7e7e7e7e7");
  receiver.init();
  /* Receiver settings done */
}

String temp_variable;
String hum_variable;

void loop(){ 
  while(receiver.available()){
    receiver.read();
    receiver.rxPL(temp_variable);
    delay(10);  
    receiver.rxPL(hum_variable); 
    
    /* Temperature and humidity datas received*/
    if(temp_variable.length()>0)
    {
      Serial.print("temperature = ");
      Serial.println(temp_variable);
      
      Serial.print("humidity = ");
      Serial.println(hum_variable);

       lcd.clear();
       lcd.setCursor(0,0);
       lcd.print("Humidity = ");
       lcd.print(hum_variable);
       lcd.setCursor(0,1);
       lcd.print("Temp = ");
       lcd.print(temp_variable);

      temp_variable="";
      hum_variable="";
      /* old datas deleted */
   }
  }
}

By the way i get the same problem with a brand new lcd and i tested the nrf24's several times. They work.

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2 
static char temp[10];
static char hum[10];

Why are your global variables static?

  dtostrf(hum_variable,5, 2, hum);
 
  dtostrf(temp_variable,5, 2, temp);

Do you REALLY believe that your temperature and humidity sensor is capable of +/- 0.01 degrees or +/- 0.01 percent humidity?

String temp_variable;
String hum_variable;

You are sending strings. Why are you receiving Strings?

Does the nRF24L01p library really know squat about Strings?

3

OK OK. I'm very new at this. So i changed my library from maniacbug version of nrf24 to tmrh version. Then i wrote a new code. This time my lcd displays NAN. I search the discussions but non of the solutions did not worked for me. here are my codes.

#include <nRF24L01.h>
#include <printf.h>
#include <RF24.h>
#include <RF24_config.h>
#include <DHT.h>

#define DHTPIN 5                // do not connect to pin 0 or pin 1
#define DHTTYPE DHT11           // Define DHT11 module
DHT dht(DHTPIN, DHTTYPE);

RF24 transmit (2,3);                            //create RF24 object called transmit
byte address [5] = "00001";                     //set address to 00001

struct package
  {
    float temperature = 0;
    float humidity = 0;
    float rainfall = 0; 
  };

typedef struct package Package;
Package data;

void setup() {
  dht.begin();
  transmit.begin();
  transmit.openWritingPipe(address);            //open writing pipe to address 00001
  transmit.setPALevel(RF24_PA_MAX);             //set RF power output to maximum
  transmit.setDataRate(RF24_250KBPS);           //set datarate to 250kbps
  transmit.setChannel(100);                     //set frequency to channel 100
  transmit.stopListening();
  }

void loop() {
  data.temperature = dht.readTemperature();
  data.humidity = dht.readHumidity();
  transmit.write(&data,sizeof(data));
  delay(1000);                                 
}

#include <nRF24L01.h>
#include <printf.h>
#include <RF24.h>
#include <RF24_config.h>
#include <LiquidCrystal.h>


RF24 receive (2,3);                         
byte address [5] = "00001";                
LiquidCrystal lcd(8,9,4,5,6,7);

int output_pin10 = 10;
int contrast = 75;

struct package
  {
    float temperature = 0;
    float humidity = 0;
  };

typedef struct package Package;
Package data;

void setup() {
  lcd.begin(16,2);
  lcd.setCursor(0,0);
  lcd.print("Receiving");
  pinMode(output_pin10, OUTPUT);
  analogWrite(output_pin10, contrast);
  receive.begin();
  receive.openReadingPipe(0,address);      
  receive.setPALevel(RF24_PA_MIN);        
  receive.setDataRate(RF24_250KBPS);      
  receive.setChannel(100);                
  receive.startListening();                
  }

void loop() {

  if (receive.available())                //check when received data available
  {
    receive.read(&data, sizeof(data));
    lcd.setCursor(0,1);
    lcd.print(data.temperature);
    lcd.print(" C  ");   
    lcd.print(data.humidity); 
    lcd.print(" % ");
    
  }
}
4 
  data.temperature = dht.readTemperature();
  data.humidity = dht.readHumidity();

You assume, quite likely incorrectly, that your sensor is connected properly and is working perfectly.

Try the examples that came with the library BEFORE you assume anything like that.

5

ok, finally i successfully make it work. thanks for your thoughts.