Other Arduino Codes and Videos by Robojax

Display Temperature from HTU21D on LCD

How use HTU21DF Humidity and Temperature Sensor with Arduino

This code displays the temperature as Celsius, Fahrenheit or Kelvin or humidity on the LCD1602-I2C or LCD2004 displays.

Resources for this sketch


  /*
 * Display Temperature from HTU21DF on LCD1602-I2C or LCD2004
 * Updated by Ahmad Shamshiri on July 13, 2019
 * in Ajax, Ontario, Canada
 * Watch video instruction for this sketch: https://youtu.be/IF46cqvKijU
**************************************************
*
  This is an example for the HTU21D-F Humidity & Temp Sensor

  Designed specifically to work with the HTU21D-F sensor from Adafruit
  ----> https://www.adafruit.com/products/1899

  These displays use I2C to communicate, 2 pins are required to
  interface

 Watch Introduction to  360 Servo video with code: https://youtu.be/b_xvu6wWafA
You can get the wiring diagram from my Arduino Course at Udemy.com
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 * Code is available at http://robojax.com/learn/arduino

 * This code is "AS IS" without warranty or liability. Free to be used as long as you keep this note intact.* 
 * This code has been download from Robojax.com
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>. 

*/

#include <Wire.h>
#include "Adafruit_HTU21DF.h"

// Connect Vin to 3-5VDC
// Connect GND to ground
// Connect SCL to I2C clock pin (A5 on UNO)
// Connect SDA to I2C data pin (A4 on UNO)

Adafruit_HTU21DF htu = Adafruit_HTU21DF();

// start of settings for LCD1602 with I2C
#include <LiquidCrystal_I2C.h>
// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x3F, 16, 2);
// end of settings for LCD1602 with I2C

void setup() {
  lcd.begin();  
  lcd.backlight();
  if (!htu.begin()) {
      lcd.print("Robojax HTUD1DF");
      lcd.setCursor(0,1);
      lcd.print("sensor missing"); 
    while (1);
  }else{
  // initialize the LCD

  lcd.print("Robojax HTUD1DF");
  lcd.setCursor(0,1);
  lcd.print("Demo"); 
  }
  delay(2000);   
}

void loop() {
   lcd.clear();// clear previous values from screen
lcdDisplay(
             // to print Celsius:
             0, // character 0 
             0, // line 0
             "Celsius: ", 

             // to print Celsius
             10, // character 10
             0, // line 0
             getHTU('C'),
             'd'
             );  

  lcdDisplay(
             // to print Fahrenheit:
             0, // character 0 
             1, // line 1
             "Fahrenh.: ", 

             // to print Fahrenheit
             10, // character 9
             1, // line 0
             getHTU('F'),
             'd'
             );     
    delay(5000);
lcdDisplay(
             // to print Kelvin:
             0, // character 0 
             0, // line 0
             "Kelvin: ", 

             // to print Celsius
             9, // character 10
             0, // line 0
             getHTU('K'),
             'k'
             );      
  lcdDisplay(
             // to print humidity text
             0, // character 0 
             1, // line 1
             "Humidity.: ", 

             // to print humidity
             10, // character 9
             1, // line 1
             getHTU('H'),
             '%' 
             );  
   
        delay(5000);
}

/*
 * @brief returns temperature or relative humidity
 * @param "type" is character
 *     C = Celsius
 *     K = Keliven
 *     F = Fahrenheit
 *     H = Humidity
 * @return returns one of the values above
 * Usage: to get Fahrenheit type: getHTU('F')
 * to print it on serial monitor Serial.println(getHTU('F'));
 * Written by Ahmad Shamshiri on July 13, 2019
 * in Ajax, Ontario, Canada
 * www.Robojax.com 
 */
float getHTU(char type)
{
  float value;
    float temp = htu.readTemperature();
    float rel_hum = htu.readHumidity();
   if(type =='F')
   {
    value = temp *9/5 + 32;//convert to Fahrenheit 
   }else if(type =='K')
   {
    value = temp + 273.15;//convert to Kelvin
   }else if(type =='H')
   {
    value = rel_hum;//return relative humidity
   }else{
    value = temp;// return Celsius
   }
   return value;
}//


/*
 * lcdDisplay(int tc, int tr, String title, int vc, int vr, float value)
 * displays value and title on LCD1602
 * How to use:
 * If you wan to diaplay: "Voltage: 13.56mV" starting from first character
 * on second row.
 * use:
 * lcdDisplay(0, 1, "Voltage: ", 13.56,'d')
 *   
 *   'd' is degree symbol
 * tc  is character number  (0)
 * tr is row in the lcd (1)
 * title is the text (Voltage:)
 * vc value for character 
 * vr value for  row or line
 * value is the value (13.56)
 */
void lcdDisplay(int tc, int tr, String title, int vc, int vr, float value,char symbol)
{
   // Robojax.com LCD1602 for HTU21D Demo
   lcd.setCursor (tc,tr); //
   lcd.print(title);
   
   lcd.setCursor (vc,vr); //
   lcd.print(value);
   if(symbol == 'd')
   {
    lcd.print((char)223);
   }else if(symbol =='%')
   {
    lcd.print("%");
   }else if(symbol =='k')
   {
    lcd.print("K");
   }
 // Robojax.com LCD1602 for HTU21D Demo
}    

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