Hello, everyone!
Is there a solution for negative Celsius readings of DHT22 sensor? I read many posts on this isue, I try everything I found about that, but no succes.
I use an Arduino Uno.
My sensor is wired as everybody says: + to Arduino's 5V; minus to Arduino's GND and data pin to pin no.2 of Arduino. And I drop it in my freezer.
The soft is an example from DHT_sensor_library_1.4.4:
// DHT Temperature & Humidity Sensor
// Unified Sensor Library Example
// Written by Tony DiCola for Adafruit Industries
// Released under an MIT license.
// REQUIRES the following Arduino libraries:
// - DHT Sensor Library: https://github.com/adafruit/DHT-sensor-library
// - Adafruit Unified Sensor Lib: https://github.com/adafruit/Adafruit_Sensor
#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <DHT_U.h>
#define DHTPIN 2 // Digital pin connected to the DHT sensor
// Feather HUZZAH ESP8266 note: use pins 3, 4, 5, 12, 13 or 14 --
// Pin 15 can work but DHT must be disconnected during program upload.
// Uncomment the type of sensor in use:
//#define DHTTYPE DHT11 // DHT 11
#define DHTTYPE DHT22 // DHT 22 (AM2302)
//#define DHTTYPE DHT21 // DHT 21 (AM2301)
// See guide for details on sensor wiring and usage:
// https://learn.adafruit.com/dht/overview
DHT_Unified dht(DHTPIN, DHTTYPE);
uint32_t delayMS;
void setup() {
Serial.begin(9600);
// Initialize device.
dht.begin();
Serial.println(F("DHTxx Unified Sensor Example"));
// Print temperature sensor details.
sensor_t sensor;
dht.temperature().getSensor(&sensor);
Serial.println(F("------------------------------------"));
Serial.println(F("Temperature Sensor"));
Serial.print (F("Sensor Type: ")); Serial.println(sensor.name);
Serial.print (F("Driver Ver: ")); Serial.println(sensor.version);
Serial.print (F("Unique ID: ")); Serial.println(sensor.sensor_id);
Serial.print (F("Max Value: ")); Serial.print(sensor.max_value); Serial.println(F("°C"));
Serial.print (F("Min Value: ")); Serial.print(sensor.min_value); Serial.println(F("°C"));
Serial.print (F("Resolution: ")); Serial.print(sensor.resolution); Serial.println(F("°C"));
Serial.println(F("------------------------------------"));
// Print humidity sensor details.
dht.humidity().getSensor(&sensor);
Serial.println(F("Humidity Sensor"));
Serial.print (F("Sensor Type: ")); Serial.println(sensor.name);
Serial.print (F("Driver Ver: ")); Serial.println(sensor.version);
Serial.print (F("Unique ID: ")); Serial.println(sensor.sensor_id);
Serial.print (F("Max Value: ")); Serial.print(sensor.max_value); Serial.println(F("%"));
Serial.print (F("Min Value: ")); Serial.print(sensor.min_value); Serial.println(F("%"));
Serial.print (F("Resolution: ")); Serial.print(sensor.resolution); Serial.println(F("%"));
Serial.println(F("------------------------------------"));
// Set delay between sensor readings based on sensor details.
delayMS = sensor.min_delay / 1000;
}
void loop() {
// Delay between measurements.
delay(delayMS);
// Get temperature event and print its value.
sensors_event_t event;
dht.temperature().getEvent(&event);
if (isnan(event.temperature)) {
Serial.println(F("Error reading temperature!"));
}
else {
Serial.print(F("Temperature: "));
Serial.print(event.temperature);
Serial.println(F("°C"));
}
// Get humidity event and print its value.
dht.humidity().getEvent(&event);
if (isnan(event.relative_humidity)) {
Serial.println(F("Error reading humidity!"));
}
else {
Serial.print(F("Humidity: "));
Serial.print(event.relative_humidity);
Serial.println(F("%"));
}
}
The Serial monitor then...:
12:08:05.635 -> Temperature: -3262.50°C
12:08:05.681 -> Humidity: 82.60%
12:08:07.650 -> Temperature: -3262.50°C
12:08:07.650 -> Humidity: 82.80%
I know that in my freezer is chilly, but not like this... 
Has anybody a solution for this problem?
Thank you!
