Hi,
I'm new with arduino
I have project, but dont know how to write code.
I have arduino uno, and dht22 sensor. I want to write code to humidifer. If room humidity is to low(40% or less, ) humidifer on till room humidity reach 60%, and so on...
Could You give me some advice or help with code?
no need to wiring, only code.
Thanks 
Regards
Mantas
Have you seen this?
Lots on the Internet.
.
i know how to test dht, but i ask how to turn on and off device(humidifer) by dht values.
Connect a relay to the humidifier,control the relay with arduino
There are examples in the IDE showing how to control an output pin.
An output can be used to operate a relay that then controls your humidifier.
.
You also need a "runtime" portion in your code where when you turn a humidifier on or off for example, it does not change state again for some minimum time (say 10 minutes). You do not want to be turning something like a humidifier on and off every 30 seconds - you will quickly kill it (and many things with compressors will not restart until they have been off for a period of time). Typically in this sort of thing, I have two things I use - one is a "deadband" with hysterisis so that it has to change some amount before it goes on or off as well as a "runtime" where once started, I run a minimum time (count down from say 10 minutes) to prevent fast cycling (if you look at smart thermostats for your house, typically, they have an adjustable "deadband" you can set).
Define variable hdtvalue as humidifier.
//global variables
// Example testing sketch for various DHT humidity/temperature sensors
// Written by ladyada, public domain
#include "DHT.h"
#define DHTPIN 2 // what digital pin we're connected to
#define relePin 3
// Uncomment whatever type you're using!
//#define DHTTYPE DHT11 // DHT 11
#define DHTTYPE DHT22 // DHT 22 (AM2302), AM2321
//#define DHTTYPE DHT21 // DHT 21 (AM2301)
// Connect pin 1 (on the left) of the sensor to +5V
// NOTE: If using a board with 3.3V logic like an Arduino Due connect pin 1
// to 3.3V instead of 5V!
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor
// Initialize DHT sensor.
// Note that older versions of this library took an optional third parameter to
// tweak the timings for faster processors. This parameter is no longer needed
// as the current DHT reading algorithm adjusts itself to work on faster procs.
DHT dht(DHTPIN, DHTTYPE);
void setup() {
Serial.begin(9600);
Serial.println("DHTxx test!");
dht.begin();
}
void loop() {
// Wait a few seconds between measurements.
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.readHumidity();
// Read temperature as Celsius (the default)
float t = dht.readTemperature();
// Read temperature as Fahrenheit (isFahrenheit = true)
float f = dht.readTemperature(true);
// Check if any reads failed and exit early (to try again).
if (isnan(h) || isnan(t) || isnan(f)) {
Serial.println("Failed to read from DHT sensor!");
return;
}
// Compute heat index in Fahrenheit (the default)
float hif = dht.computeHeatIndex(f, h);
// Compute heat index in Celsius (isFahreheit = false)
float hic = dht.computeHeatIndex(t, h, false);
if (h > 60.0)
// turn on rele
digitalWrite(relePin, HIGH);
fi (h < 57.0) // 3.0 histeresis
// turn off rele
digitalWrite(relePin, LOW);
Serial.print("Humidity: ");
Serial.print(h);
Serial.print(" %\t");
Serial.print("Temperature: ");
Serial.print(t);
Serial.print(" *C ");
Serial.print(f);
Serial.print(" *F\t");
Serial.print("Heat index: ");
Serial.print(hic);
Serial.print(" *C ");
Serial.print(hif);
Serial.println(" *F");
}
Thanks
Other problem,
'surbyte's code works perfect, now i want to turn on an off other device, but if i put this
digitalWrite(11, HIGH); // turn on
delay(10000); // wait for a 10s
digitalWrite(11, LOW); // turn off
delay(10000); // wait for a 10s
in 'void loop' its not working as i want,
I want it works independently
like separate loops
hope you understand me : )
Search the forum here for the "blink without delay" topic. Basically, the delay() function is blocking - it takes up all the processor time until it counts down to whatever is the end of it's time then lets execution continue. You have to do it differently by setting a timer and checking it periodically in your code so the processor can do other things but checks the time until it gets to zero.
to difficult for me 