DHT11 & Relay Arduino Uno

Using Arduino Programming Questions
1

Hi All,

Wondering of anyone could shed some light on why the relay is not activating with this code.

Sorry of this is simple, I'm new to Arduino.

#include <dht.h>
dht DHT;

#define DHT11_PIN 7
int relay = 8;

void setup(){
 Serial.begin(9600);
 pinMode(relay, OUTPUT);
}

void loop() 
{
 int chk = DHT.read11(DHT11_PIN);
 Serial.print("Temperature = ");
 Serial.println(DHT.temperature);
 Serial.print("Humidity = ");
 Serial.println(DHT.humidity);
 delay(5000);
   
if("Temperature" > 31, relay, HIGH);
if("Temperature" < 16, relay, HIGH); //Sets off relay if Temperature is out of range

delay (8000);
digitalWrite(relay, LOW);

}
2

Please read the "How to use this forum" post and please use code tags when posting code.

if("Temperature" > 31, relay, HIGH);

You're comparing a string of text to a number. That's not making any sense.

if(DHT.temperature > 31, relay, HIGH);

That might make more sense. That's where you're getting the number from in the other part of the code where you printed it to the serial monitor.

3

If using code tages (</>), your program codes would appear like this (minor changes are done):

#include <dht.h>
dht DHT;

#define DHT11_PIN 7
int relay = 8;

void setup() 
{
  Serial.begin(9600);
  pinMode(relay, OUTPUT);
}

void loop()
{
  int chk = DHT.read11(DHT11_PIN);
  Serial.print("Temperature = ");
  Serial.println(DHT.temperature);
  Serial.print("Humidity = ");
  Serial.println(DHT.humidity);
  delay(5000);

  if (DHT.temperature > 31)//("Temperature" > 31, relay, HIGH);
  {
    digitalWrite(relay, HIGH);
  }

  if (DHT.temperature < 16)//("Temperature" < 16, relay, HIGH); //Sets off relay if Temperature is out of range
  {
    digitalWrite(relay, LOW);
  }
  delay (8000);
  //digitalWrite(relay, LOW);
}
4 
if("Temperature" > 31, relay, HIGH);

Once you fix the problem of comparing a number with a string check that the brackets in your test are in the right place

if (something > 31)  //that's the test
{
  //the code to run if the test returns true goes here outside of the brackets of the test
}
5

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html .
Then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.

Thanks.. Tom... :slight_smile:

6

Thanks for the help, works great

7

Ok so I've taken the same idea and applied it to a Thinger code so I can monitor from the web.

Getting an error I haven't come across before?

In function 'global constructors keyed to 65535_0_thinger_trial_testing_DHT11_v1.1.ino.cpp.o':
lto1.exe: internal compiler error: Segmentation fault
Please submit a full bug report,
with preprocessed source if appropriate.
See http://gcc.gnu.org/bugs.html for instructions.
lto-wrapper.exe: fatal error: C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.21.0_x86__mdqgnx93n4wtt\hardware\tools\avr/bin/avr-gcc returned 1 exit status
compilation terminated.
c:/program files/windowsapps/arduinollc.arduinoide_1.8.21.0_x86__mdqgnx93n4wtt/hardware/tools/avr/bin/../lib/gcc/avr/5.4.0/../../../../avr/bin/ld.exe: error: lto-wrapper failed

collect2.exe: error: ld returned 1 exit status

Anyone shed some light on this? Thanks

#include <DHT.h>
#include <SPI.h>
#include <Ethernet.h>
#include <ThingerEthernet.h>

// dht config
#define DHTPIN 7
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);
int relay = 10;


// thinger.io config
ThingerEthernet thing("username", "xxxxxx", "xxxx");

void setup() {
  dht.begin();
  pinMode(relay, OUTPUT); //sets pin8 as relay output
  
  thing["RoomMonitor"] >> [](pson& out){
    out["Humidity"] = dht.readHumidity();
    out["Temperature"] = dht.readTemperature();
    
};
}

void loop() {  
    thing.handle();

if(dht.readTemperature() < 16) digitalWrite(relay, HIGH);

if(dht.readTemperature() > 31) digitalWrite(relay, HIGH);

delay (10000);

digitalWrite(relay, LOW);//Reset Alarm Relay
}