Hello everyone,
I am currently working on a hydroponics automation project for my college assignment. I have been testing my DHT22 interfaced with Arduino Mega 2560 for a few days, trying to troubleshoot a problem with its readings.
The readings are wildly off and the humidity reads as 2201% and temperature as 761*C. I have tried several libraries including the Adafruit's library, nethoncho's library, the one provided by cactus.io. Yet it still showed the same values. The connections are correct, I am even using a pull up resistor of 10K. The data pin is connected to Pin 12 of Arduino Mega.
Is it that my sensor is faulty or it has to do with my polling intervals? I am using the standard delay of 2 seconds, as suggested by the data sheet. I've looked through several related forum posts for this, but I did not come across such an issue yet.
Here's my code:
// Example sketch for DHT22 humidity - temperature sensor
// Written by cactus.io, with thanks to Adafruit for bits of their library. public domain
#include "cactus_io_DHT22.h"
#define DHT22_PIN 12 // what pin on the arduino is the DHT22 data line connected to
// For details on how to hookup the DHT22 sensor to the Arduino then checkout this page
// http://cactus.io/hookups/sensors/temperature-humidity/dht22/hookup-arduino-to-dht22-temp-humidity-sensor
// Initialize DHT sensor for normal 16mhz Arduino.
DHT22 dht(DHT22_PIN);
// Note: If you are using a board with a faster processor than 16MHz then you need
// to declare an instance of the DHT22 using
// DHT22 dht(DHT22_DATA_PIN, 30);
// The additional parameter, in this case here is 30 is used to increase the number of
// cycles transitioning between bits on the data and clock lines. For the
// Arduino boards that run at 84MHz the value of 30 should be about right.
void setup() {
Serial.begin(9600);
Serial.println("DHT22 Humidity - Temperature Sensor");
Serial.println("RH\t\tTemp (C)\tTemp (F)\tHeat Index (C)\t Heat Index (F)");
dht.begin();
}
void loop() {
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
dht.readHumidity();
dht.readTemperature();
// Check if any reads failed and exit early (to try again).
if (isnan(dht.humidity) || isnan(dht.temperature_C)) {
Serial.println("DHT sensor read failure!");
return;
}
Serial.print(dht.humidity); Serial.print(" %\t\t");
Serial.print(dht.temperature_C); Serial.print(" *C\t");
Serial.print(dht.temperature_F); Serial.print(" *F\t");
Serial.print(dht.computeHeatIndex_C()); Serial.print(" *C\t");
Serial.print(dht.computeHeatIndex_F()); Serial.println(" *F");
// Wait a few seconds between measurements. The DHT22 should not be read at a higher frequency of
// about once every 2 seconds. So we add a 3 second delay to cover this.
delay(2500);
}
This is the output I am getting at the serial monitor:
