DHT21 / AM2301A Temperature and Humidity Sensor

Name: DHT21 / AM2301A Temperature and Humidity Sensor
Brand: ESP32
Price: 5 USD
Availability: InStock

DHT21 / AM2301A Temperature and Humidity Sensor image

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Overview

The DHT21 is a reliable sensor for measuring temperature and humidity, offering calibrated digital output and ease of integration with microcontrollers. With a temperature measurement range of -40°C to 80°C and a humidity range of 0% to 100%, the DHT21 is suitable for various applications, including environmental monitoring and HVAC systems.

Quick Navigation

📋 Specs 📍 Pinout 🔌 Wiring 🔧 Debug

Code Examples

Arduino

C++ Framework

ESP-IDF

Native Framework

ESPHome

YAML Configuration

PlatformIO

IDE & Toolchain

MicroPython

Python Framework

About DHT21 / AM2301A Temperature and Humidity Sensor

The DHT21, also known as AM2301, is a digital temperature and humidity sensor that provides accurate environmental measurements. It uses a capacitive humidity sensor and a thermistor to ensure reliable data collection.

⚡ Key Features

High Accuracy – Delivers precise temperature and humidity readings.
Single-Wire Digital Communication – Easy integration with ESP32, Arduino, and other microcontrollers.
Capacitive Humidity Sensing – Provides stable and long-term performance.
Similar to DHT22 – Slight differences in casing and specifications.

With its ease of use and reliable performance, the DHT21 is ideal for climate monitoring, smart home systems, and industrial automation. 🚀

Where to Buy

Get Your DHT21 / AM2301A

DHT21 / AM2301A Temperature and Humidity Sensor

Starting from

$5 per unit

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💡 Prices are subject to change. We earn from qualifying purchases as an Amazon Associate.

Technical Specs

DHT21 / AM2301A Specifications

Complete technical specification details for DHT21 / AM2301A Temperature and Humidity Sensor

📊 Technical Parameters

Operating Voltage 3.3V to 5.5V

Temperature Range -40°C to 80°C

Humidity Range 0% to 100% RH

Temperature Accuracy ±0.5°C

Humidity Accuracy ±3% RH

Sampling Rate 0.5 Hz (once every 2 seconds)

Dimensions 59mm x 27mm x 13.5mm

Download Full Datasheet

Pin Configuration

DHT21 / AM2301A Pinout

The DHT21/AM2301A features the same 4-pin layout as DHT22, with nearly identical specifications and performance.

Visual Pinout Diagram

Pinout Diagram Primary

DHT21 / AM2301A Temperature and Humidity Sensor pinout

Total Pins

Pin Types

Power

Communication

Control

Quick Tips

🔌

Uses same single-wire protocol as DHT22,⚠️ Requires 5kΩ to 10kΩ pull-up resistor on DATA pin

💡

Nearly identical to DHT22 in performance,⏱️ Read interval of 2 seconds minimum

🌡️

Wide temperature range (-40°C to 80°C)

Pin Descriptions

Pin Name	Type	Description	Notes
1 VCC	Power	Power supply input (3.3V to 6V)	Compatible with both 3.3V and 5V systems
2 DATA	Communication	Digital signal output	Single-wire digital interface for data
3 NC	Control	Not connected	Leave this pin unconnected
4 GND	Power	Ground connection	Connect to ESP32 ground

Connection Guide

Wiring DHT21 / AM2301A to ESP32

Connect the DHT21/AM2301A using the single-wire digital interface, identical to DHT22 wiring.

Visual Wiring Diagram

Wiring Diagram Recommended

DHT21 / AM2301A Temperature and Humidity Sensor wiring with ESP32

Connections

Connection Status

Required

Protocol

OneWire

Pin Connections

DHT21 / AM2301A Pin	ESP32 Pin	Description
1 VCC Required	3.3V	Power supply (3.3V to 6V supported)
2 GND Required	GND	Ground connection
3 DATA Required	GPIO4	Digital data line
4 DATA (Pull-up) Required	5kΩ to VCC	Pull-up resistor for reliable data transfer

💡

Any GPIO pin works - GPIO4 is commonly used

🔧

5kΩ pull-up resistor recommended (10kΩ also works)

⚡

Use 3.3V for ESP32 compatibility

⏱️

Minimum 2 second delay between readings

🔄

Compatible with DHT22 libraries and code

Help & Support

DHT21 / AM2301A Troubleshooting

Common issues and solutions to help you get your sensor working

Common Issues

Debugging Tips

Additional Resources

Datasheet

Technical specifications and guidelines

Code Examples

DHT21 / AM2301A Programming Examples

Ready-to-use code examples for different platforms and frameworks

#include "DHT.h"

#define DHTPIN 4     // Digital pin connected to the DHT sensor
#define DHTTYPE DHT21   // DHT 21 (AM2301)

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(115200);
  Serial.println("DHT21 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 DHT21 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.

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#include "dht.h"

#define DHT_PIN GPIO_NUM_4

void app_main() {
    setDHTgpio(DHT_PIN);

    while (1) {
        printf("Reading DHT21 sensor...\n");

        int ret = readDHT();
        errorHandler(ret);

        printf("Humidity: %.1f%%\n", getHumidity());
        printf("Temperature: %.1f°C\n", getTemperature());

        vTaskDelay(2000 / portTICK_PERIOD_MS);
    }
}

This ESP-IDF example demonstrates how to read data from the DHT21 sensor using GPIO pin 4. The `readDHT()` function reads the sensor data, and the humidity and temperature values are retrieved using `getHumidity()` and `getTemperature()` functions, respectively. The readings are printed to the console every 2 seconds.

sensor:
  - platform: dht
    pin: GPIO4
    model: DHT21
    temperature:
      name: "Living Room Temperature"
    humidity:
      name: "Living Room Humidity"
    update_interval: 60s

The ESPHome configuration defines the DHT21 sensor using the `dht` platform. The `pin` specifies the GPIO pin (e.g., GPIO4) where the sensor's DATA pin is connected. The `model` is set to `DHT21` to ensure correct data handling. Two sensors are configured: one for temperature and one for humidity, each with descriptive names such as 'Living Room Temperature' and 'Living Room Humidity.' The `update_interval` is set to 60 seconds, meaning the sensor will provide new data every minute.

platformio.ini

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
lib_deps = 
    adafruit/DHT sensor library @ ^1.4.2
monitor_speed = 115200

main.cpp

#include <DHT.h>

#define DHTPIN 4
#define DHTTYPE DHT21

DHT dht(DHTPIN, DHTTYPE);

void setup() {
    Serial.begin(115200);
    Serial.println("DHT21 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 code demonstrates interfacing the DHT21 sensor with an ESP32 board. It initializes the sensor on GPIO pin 4, reads the temperature and humidity values every 2 seconds, and outputs the data to the Serial Monitor. The code includes checks for invalid readings and retries if necessary.

from machine import Pin
from time import sleep
import dht

# Initialize the DHT21 sensor
sensor = dht.DHT21(Pin(4))

print('DHT21 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 script uses the `dht` module to interact with the DHT21 sensor. The sensor is initialized on GPIO pin 4, and readings are taken every 2 seconds. The `sensor.measure()` method updates the data, and `sensor.temperature()` and `sensor.humidity()` retrieve the temperature and humidity values, respectively. The results are printed to the console in a user-friendly format.

Summary

Wrapping Up DHT21 / AM2301A

The ESP32 DHT21 / AM2301A Temperature and Humidity Sensor is a powerful environment sensor that offers excellent performance and reliability. With support for multiple development platforms including Arduino, ESP-IDF, ESPHome, PlatformIO, and MicroPython, it's a versatile choice for your IoT projects.