Class for DHT11, DHT21 and DHT22 (temperature & humidity)

Hi Terry, i´m new with Arduino and my first project is building a temperature-regulator. just i see your project and take parts from your code, but i can not see negative values on my display. have you got an idea, which part i must change? Sorry, i´m newbie and my english is not the best, but i hope, you or everyone can help...

thank you

olli

/*
Basierend auf einen Artikel auf dieser Seite:
http://arduino-info.wikispaces.com/PROJECT-Temp-Humidity-Display

den aktuellen Stand findest Du hier:
http://alturl.com/rpods
*/
 
/*-----( Import needed libraries )-----*/
#include <dht11.h>
#include <Wire.h>
#include <LiquidCrystal.h>
/*-----( Declare objects )-----*/
LiquidCrystal lcd(8, 9, 4, 5, 6, 7); //##### DFRobot LCD Keypadshield V1.0
 // legt die pins auf dem shield fest

/* begin des tastatur-bereichs */
int lcd_key = 0; // legt nutzung der tasten fest und dann die tasten selber
int adc_key_in = 0;
#define btnRIGHT 0
#define btnUP 1
#define btnDOWN 2
#define btnLEFT 3
#define btnSELECT 4
#define btnNONE 5
/* ab hier: einlesen der werte der tasten (wiederstands gebilde mit
unterschiedlichen spannungswerten zu jeder taste...*/

int read_LCD_buttons()
 {
 adc_key_in = analogRead(0); // read the value from the sensor 
 // my buttons when read are centered at these valies: 0, 144, 329, 504, 741
 // we add approx 50 to those values and check to see if we are close
 if (adc_key_in > 1000) return btnNONE; // We make this the 1st option for speed reasons
since it will be the most likely result
 if (adc_key_in < 50) return btnRIGHT; 
 if (adc_key_in < 195) return btnUP; 
 if (adc_key_in < 380) return btnDOWN; 
 if (adc_key_in < 555) return btnLEFT; 
 if (adc_key_in < 790) return btnSELECT; 
 return btnNONE; // when all others fail, return this...
 }
/* das wars mit dem tastatur-bereich */

dht11 DHT11;
/*-----( Declare Constants, Pin Numbers )-----*/
#define DHT11PIN 2

float alarmwert (20);
 
void setup() /*----( SETUP: RUNS ONCE )----*/
{
 Serial.begin(9600); 
 lcd.begin(16,2); //##### Display Size for DFRobot LCD Keypadshield V1.0
 lcd.home ();
 lcd.println ("Olliduino "); //##### schreibe willkommensnachricht und springe eine zeile weiter
 lcd.setCursor (0,1);
 lcd.print ("2011 by olli "); //##### schreibe willkommensnachricht
 lcd.home ();
 delay(3000);
 lcd.clear ();
 
}/*--(end setup )---*/
  

void loop() /*----( LOOP: RUNS CONSTANTLY )----*/
{

 // digitalWrite(13, HIGH);

 
 int chk = DHT11.read(DHT11PIN);
 
 Serial.println("---------------------------"); //der Lesbarkeit erstmal eine Zeile
 switch (chk) // teste, ob ueberhaupt daten fliessen
 {
 case 0: Serial.println("DHT11 ist OK");
 Serial.print ("gelieferter Wert: ");
 Serial.println ((float)DHT11.temperature,1); 
 break;
 case -1: Serial.println("Checksum error"); break;
 case -2: Serial.println("Time out error"); break;
 default: Serial.println("Unknown error"); break;
 }
Serial.print((float)alarmwert, 1);
 Serial.println("C Darunter-Gibt-es-ALARM-Temperatur");
 Serial.print((float)DHT11.temperature,1);
 Serial.println("C IST-Temperatur");
if ( DHT11.temperature < alarmwert ) 
 { 
 digitalWrite(13, HIGH);
 Serial.println("### !!! Alarm erreicht !!! ###"); 
 lcd.setCursor (15,0); //##### schreibe ab zeichen 14 in zeile 1 (zeile 1 ist gleich 0)
 lcd.print("!");
 lcd.setCursor (0,1);
 }
else
 {
 digitalWrite(13, LOW);
 Serial.println("Alarm nicht erreicht, alles OK");
 lcd.setCursor (15,0); //##### schreibe ab zeichen 14 in zeile 1 (zeile 1 ist gleich 0)
 lcd.print("*");
 lcd.setCursor (0,1);
 }

 
 //lcd.noAutoscroll();
 lcd.setCursor (0,1);
 lcd.print(alarmwert,0);
 lcd.print("Cs ");
 lcd.print((float)DHT11.temperature,1);
 lcd.print("Ci ");
 lcd.print((float)DHT11.humidity,1);
 lcd.print("%");

 digitalWrite(13, LOW);
 
 delay(1000);
 
 
 
 
 // jetzt lesen wir noch die tasten ein und machen was draus
 
 lcd_key = read_LCD_buttons(); // read the buttons
switch (lcd_key) // depending on which button was pushed, we perform an action
 {
 case btnRIGHT:
 {
 lcd.setCursor (0,0);
 lcd.print("> ");
 break;
 }
 case btnLEFT:
 {
 lcd.setCursor (0,0);
 lcd.print("<");
 break;
 }
 case btnUP:
 {
 alarmwert = alarmwert + 1;
 lcd.setCursor (0,0);
 lcd.print("^");
 break;
 }
 case btnDOWN:
 {
 alarmwert = alarmwert - 1;
 lcd.setCursor (0,0);
 lcd.print("v");
 break;
 }
 case btnSELECT:
 {
 lcd.setCursor (0,0);
 lcd.print("*");
 break;
 }
 case btnNONE:
 {
 lcd.setCursor (0,0);
 lcd.print(" ");
 break;
 }
 } 
 
 
 
 
 
 
 
 
 
 
}
/* --(end main loop )-- */