DHT22 / AM2302 Temperature and Humidity Sensor
The DHT22 is a versatile and affordable sensor for measuring temperature and humidity. It provides calibrated digital output and is easy to interface with microcontrollers. With a temperature measurement range of -40°C to 80°C and humidity range of 0% to 100%, the DHT22 is suitable for a variety of applications, including environmental monitoring and HVAC systems.
DHT22 / AM2302 pinout
The DHT22/AM2302 uses the same 4-pin layout as the DHT11, with improved accuracy and wider measurement range.
| Pin | Type | Description | Notes |
|---|---|---|---|
| VCC | Power | Power supply input (3.3V to 6V) | Works with both 3.3V and 5V logic levels |
| DATA | Communication | Digital signal output | Single-wire digital interface for data transmission |
| NC | Control | Not connected | Leave this pin unconnected |
| GND | Power | Ground connection | Connect to ESP32 ground |
Uses proprietary single-wire digital protocol
Requires 5kΩ to 10kΩ pull-up resistor on DATA pin
Higher accuracy than DHT11 (±0.5°C vs ±2°C)
Can be read once every 2 seconds
Operates in wider temperature range (-40°C to 80°C)
Wiring the DHT22 / AM2302 to ESP32
Connect the DHT22/AM2302 using the single-wire digital interface with a pull-up resistor for stable readings.
| DHT22 / AM2302 pin | ESP32 pin | Purpose |
|---|---|---|
| VCC | 3.3V | Power supply (3.3V to 6V supported) |
| GND | GND | Ground connection |
| DATA | GPIO4 | Digital data line |
| DATA (Pull-up) | 5kΩ to VCC | Pull-up resistor for reliable communication |
Any GPIO pin works - GPIO4 is commonly used
5kΩ pull-up resistor recommended (10kΩ also works)
Use 3.3V for ESP32, sensor supports up to 6V
Minimum 2 second interval between readings
Better accuracy than DHT11 for demanding applications
DHT22 / AM2302 code examples
#include "DHT.h"
#define DHTPIN 4 // Digital pin connected to the DHT sensor
#define DHTTYPE DHT22 // DHT 22 (AM2302)
DHT dht(DHTPIN, DHTTYPE);
void setup() {
Serial.begin(115200);
Serial.println("DHT22 Sensor Example");
dht.begin();
}
void loop() {
// Wait a few seconds between measurements
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
float humidity = dht.readHumidity();
// Read temperature as Celsius (the default)
float temperature = dht.readTemperature();
// Check if any reads failed and exit early (to try again).
if (isnan(humidity) || isnan(temperature)) {
Serial.println("Failed to read from DHT sensor!");
return;
}
Serial.print("Humidity: ");
Serial.print(humidity);
Serial.print(" % ");
Serial.print("Temperature: ");
Serial.print(temperature);
Serial.println(" °C");
}This Arduino sketch demonstrates how to interface with the DHT22 sensor. It initializes the sensor on digital pin 4 and reads the temperature and humidity every 2 seconds. The readings are then printed to the Serial Monitor. The code includes checks to ensure that the sensor readings are valid.
// Requires the esp-idf-lib DHT driver (ESP Component Registry):
// idf.py add-dependency "esp-idf-lib/dht^1.2.0"
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "dht.h"
#define DHT_GPIO GPIO_NUM_4
#define DHT_TYPE DHT_TYPE_AM2301 // DHT22 / AM2302
void app_main(void)
{
float hum, temp;
while (1) {
if (dht_read_float_data(DHT_TYPE, DHT_GPIO, &hum, &temp) == ESP_OK) {
printf("Hum %.1f%% Temp %.1f C\n", hum, temp);
} else {
printf("Could not read data from sensor\n");
}
vTaskDelay(pdMS_TO_TICKS(2000));
}
}ESP-IDF ships no DHT driver of its own, so this example uses the maintained esp-idf-lib DHT driver from the ESP Component Registry. Install it into your project first with idf.py add-dependency "esp-idf-lib/dht^1.2.0", then build as usual.
dht_read_float_data() performs one complete read and fills in the humidity and temperature values, returning ESP_OK on success. DHT_TYPE_AM2301 is the correct sensor type for the DHT22 (also sold as AM2302); for a DHT11 use DHT_TYPE_DHT11 instead. No extra include is needed for GPIO_NUM_4 - dht.h pulls in the GPIO driver. The loop prints a reading every 2 seconds, matching the sensor's 0.5 Hz sampling rate.
sensor:
- platform: dht
pin: GPIO4
model: DHT22
temperature:
name: "Living Room Temperature"
humidity:
name: "Living Room Humidity"
update_interval: 60sThe ESPHome configuration utilizes the dht platform to define the DHT22 sensor. The pin specifies the GPIO pin where the sensor’s DATA pin is connected (e.g., GPIO4). The model is set to DHT22 to ensure accurate data interpretation. Two sensor entities are defined: one for temperature and one for humidity, each assigned a user-friendly name like ‘Living Room Temperature’ and ‘Living Room Humidity.’ The update_interval is set to 60 seconds, meaning the sensor will update the readings every minute.
[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
lib_deps =
adafruit/DHT sensor library @ ^1.4.2
monitor_speed = 115200#include <DHT.h>
#define DHTPIN 4
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);
void setup() {
Serial.begin(115200);
Serial.println("DHT22 Sensor Example");
dht.begin();
}
void loop() {
// Wait a few seconds between measurements
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
float humidity = dht.readHumidity();
// Read temperature as Celsius (the default)
float temperature = dht.readTemperature();
// Check if any reads failed and exit early (to try again).
if (isnan(humidity) || isnan(temperature)) {
Serial.println("Failed to read from DHT sensor!");
return;
}
Serial.print("Humidity: ");
Serial.print(humidity);
Serial.print(" % ");
Serial.print("Temperature: ");
Serial.print(temperature);
Serial.println(" °C");
}This PlatformIO sketch demonstrates how to use the DHT22 sensor with an ESP32 board. It initializes the sensor on GPIO pin 4 and reads temperature and humidity data every 2 seconds. The results are printed to the Serial Monitor. The code includes checks to ensure the sensor data is valid, retrying if the readings are invalid.
from machine import Pin
from time import sleep
import dht
# Initialize the DHT22 sensor
sensor = dht.DHT22(Pin(4))
print('DHT22 Sensor Example')
while True:
sensor.measure()
temperature = sensor.temperature() # Temperature in Celsius
humidity = sensor.humidity() # Relative Humidity in %
print('Temperature: {} °C'.format(temperature))
print('Humidity: {} %'.format(humidity))
sleep(2)This MicroPython code uses the dht module to interact with the DHT22 sensor. It initializes the sensor on GPIO pin 4, reads temperature and humidity every 2 seconds, and prints the results to the console. The sensor.measure() function is used to fetch the data from the sensor, and the temperature() and humidity() methods are used to extract the values.
DHT22 / AM2302 specifications
About the DHT22 / AM2302
The DHT22 (also sold wired into a housing as the AM2302) is the DHT11’s more capable sibling: the same capacitive-humidity-plus-thermistor design and single-wire digital protocol, but with markedly better numbers - ±0.5 degC and ±2% RH accuracy over a much wider -40 to 80 degC range, against the DHT11’s ±2 degC / ±5% RH and 0-50 degC ceiling.
The tradeoff is that the DHT22’s single-wire timing is tighter than the DHT11’s, and it’s genuinely sensitive to wiring: multiple independent reports trace intermittent read failures to long cable runs, where the added capacitance rounds off the signal’s rising edges until the sensor stops responding reliably. Keep the data line short, use a solid pull-up, and consider a twisted pair with a shared ground if you need to run it more than a meter or two. Expect one reading every 2 s (0.5 Hz) at best.
For the price, the DHT22’s ±2% RH humidity accuracy is no longer class-leading - I2C sensors like the SHT40 match or beat it while skipping the timing-critical wiring entirely - but the DHT22 remains a solid, thoroughly documented choice, especially if you need its wide temperature range or already have code built around it. If only temperature matters, the DS18B20 covers a wider range still; for less accuracy at a lower price, there’s the DHT11.
DHT22 / AM2302 troubleshooting
Failed to Read from DHT Sensor
›
Issue: Receiving 'Failed to read from DHT sensor!' or NaN readings when attempting to retrieve data from the DHT22 (AM2302) sensor.
Possible causes include incorrect wiring, insufficient power supply, or improper sensor initialization.
Solution: Double-check the wiring connections: ensure VCC is connected to 3V to 6V, GND to ground, and the data pin to the appropriate GPIO pin on the microcontroller. Verify that a suitable pull-up resistor (typically 5kΩ) is connected between the data pin and VCC. Ensure the sensor is properly initialized in the code, and that the correct sensor type is specified in the library. Additionally, consider increasing the time between sensor readings, as the DHT22 has a sampling rate of once every 2 seconds.
Incorrect Readings at Sub-Zero Temperatures
›
Issue: The DHT22 sensor provides incorrect temperature readings when the ambient temperature falls below 0°C (32°F).
Possible causes include limitations in the sensor's design or firmware that affect accuracy at low temperatures.
Solution: Be aware that the DHT22 may have reduced accuracy at temperatures below freezing. For applications requiring precise measurements in sub-zero conditions, consider using a sensor specifically designed for low-temperature accuracy.
Sensor Stops Responding After Prolonged Use
›
Issue: The DHT22 sensor ceases to provide valid readings after extended periods of operation, requiring a reset to resume functionality.
Possible causes include sensor lockup due to environmental factors or power supply instability.
Solution: Implement periodic sensor resets in your code to mitigate potential lockups. Ensure a stable power supply and consider adding decoupling capacitors to filter out noise. If the problem persists, evaluate the operating environment for factors that may adversely affect the sensor's performance.
Interference with Other I2C Devices
›
Issue: Connecting the DHT22 sensor alongside other I2C devices causes communication issues or device malfunctions.
Possible causes include the DHT22's communication protocol conflicting with I2C devices.
Solution: The DHT22 uses a proprietary single-wire protocol and does not operate on the I2C bus. Ensure that the sensor is connected to a dedicated GPIO pin and that its communication does not interfere with I2C devices. If issues persist, consider isolating the sensor's data line from the I2C bus.
Where to buy the DHT22 / AM2302
Resources
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