Overview

The DHT22 (also sold as AM2302) is a high-precision digital temperature and humidity sensor manufactured by Aosong Electronics. It serves as an accuracy upgrade to the basic DHT11, offering wider measurement ranges, 16-bit high-resolution output, sub-zero temperature capability, and decimal precision.

It incorporates a capacitive humidity sensor element, a high-precision NTC thermistor, and a 8-bit microcontroller that outputs a calibrated 40-bit digital signal over a single-bus interface.

Quick reference

Operating voltage (VCC)3.3 V to 6.0 V DC (5 V recommended)
Humidity range0% to 100% RH (±2.0% RH\pm 2.0\%\text{ RH} accuracy)
Temperature range−40∘C-40^\circ\text{C} to +80∘C+80^\circ\text{C} (±0.5 ∘C\pm 0.5\text{ }^\circ\text{C} accuracy)
Resolution16-bit (0.1% RH, 0.1 °C resolution)
Sampling period2.0 seconds (do not sample faster than 0.5 Hz)
InterfaceCustom Single-Bus 1-Wire protocol
Active measuring current1.0 mA to 1.5 mA

Pinout

4-Pin Single In-line Package / 3-Pin Breakout

PinNameTypeDescription
1VCCPowerSupply voltage (+3.3 V to +6.0 V DC)
2DATADigital I/OSingle-bus bidirectional data line (requires 1kΩ–10kΩ pull-up)
3NCNot ConnectedDo not connect
4GNDPowerGround (0 V)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVCCV_{CC}3.35.06.0VDC
Measuring CurrentIDDI_{DD}1.01.52.1mADuring data transmission
Standby CurrentISBI_{SB}405060µABetween measurements
Humidity Measuring RangeRHRH0—100% RH
Humidity AccuracyΔRH\Delta RH-2.0—+2.0% RHAt 25∘C25^\circ\text{C}
Humidity ResolutionRHresRH_{res}—0.1—% RH16-bit data
Temp Measuring RangeTT-40—80°C
Temp AccuracyΔT\Delta T-0.5—+0.5°C
Temp ResolutionTresT_{res}—0.1—°C16-bit data
Data Response Timetreadt_{read}—2.0—sMinimum interval between reads

Communication protocol

The DHT22 uses a single-bus protocol sending a 40-bit (5-byte) frame. Unlike the DHT11, both humidity and temperature values are 16-bit signed values multiplied by 10:

Data Packet=Humidity High≪8∣Humidity Low⏟16-bit RH ×10+Temp High≪8∣Temp Low⏟16-bit Temp ×10+Checksum⏟Byte 4\text{Data Packet} = \underbrace{\text{Humidity High} \ll 8 \mid \text{Humidity Low}}_{\text{16-bit RH } \times 10} + \underbrace{\text{Temp High} \ll 8 \mid \text{Temp Low}}_{\text{16-bit Temp } \times 10} + \underbrace{\text{Checksum}}_{\text{Byte 4}}

  • Negative Temperatures: If bit 15 (MSB) of the Temperature word is 1, the temperature is negative. Clear bit 15 and multiply by -0.1.
  • Checksum Formula: Byte 4=(Byte 0+Byte 1+Byte 2+Byte 3)(mod256)\text{Byte 4} = (\text{Byte 0} + \text{Byte 1} + \text{Byte 2} + \text{Byte 3}) \pmod{256}.
  • Timing: MCU pulls DATA LOW for 1 to 10 ms, then releases. DHT22 responds with 80 µs LOW + 80 µs HIGH, followed by 40 data bits (50 µs LOW baseline; 26 µs HIGH = 0, 70 µs HIGH = 1).

Wiring

DHT22 / AM2302→Microcontroller (Arduino Uno / ESP32)Notes
VCC5V (or 3.3V)Power supply
DATADigital GPIO Pin (e.g. GPIO4)Requires 4.7 kΩ4.7\text{ k}\Omega–10 kΩ10\text{ k}\Omega pull-up resistor to VCC
GNDGNDGround

Common mistakes

  • Polling faster than 0.5 Hz (every 2 seconds): The DHT22 requires 2 seconds between measurements to allow internal sensor element stabilization. Requesting data too quickly results in reading errors or internal self-heating.
  • Using DHT11 driver code for DHT22: While the physical signaling waveform is identical, the data payload decoding differs. DHT11 sends 8-bit integer bytes, whereas DHT22 sends 16-bit values with decimal multipliers.
  • Inadequate pull-up resistor on long wires: For cables longer than 5 meters, use a 1 kΩ1\text{ k}\Omega to 2.2 kΩ2.2\text{ k}\Omega pull-up resistor to ensure fast signal rise times.

Notes

  • AM2302 is the module version of the DHT22, often pre-wired with flexible lead wires and an internal pull-up resistor.

Assets & downloads