The DHT11 is one of the most widely used digital temperature and humidity sensors in Arduino and electronics projects. It measures both temperature and relative humidity using a single digital output pin, and is commonly found in weather stations, HVAC systems, greenhouses, and home automation projects.
What is DHT11?
The DHT11 is a basic integrated sensor module that measures ambient temperature and relative humidity. Unlike analog sensors, it outputs calibrated digital data through a single-wire serial interface, making it straightforward to read with any microcontroller.
One of the biggest advantages of the DHT11 is its all-in-one design — it measures two environmental parameters simultaneously with a single sensor. This eliminates the need for separate sensors and simplifies wiring in projects that require both temperature and humidity monitoring.
DHT11 overview
| Parameter | Value |
|---|---|
| Sensor Type | Digital Temperature & Humidity Sensor |
| Operating Voltage | 3.3V – 5.5V |
| Current Consumption | 2.5mA (during measurement) |
| Temperature Range | 0°C to +50°C |
| Humidity Range | 20% to 80% RH |
| Output Type | Digital (Single-Wire) |
| Temperature Accuracy | ±2°C |
| Humidity Accuracy | ±5% RH |
| Communication | Single-Wire Serial |
| Mounting Type | Through Hole |
| Compatible Boards | Arduino Uno, ESP32, Raspberry Pi |
Pinout
| Pin Name | Type | Description |
|---|---|---|
| VCC | Power | Supplies power to the sensor (3.3V – 5.5V) |
| DATA | Output | Sends digital temperature and humidity data |
| NC | — | Not connected (no function) |
| GND | Power | Ground connection |
Note: A pull-up resistor of 4.7kΩ – 10kΩ is recommended between the DATA pin and VCC for reliable communication, especially over longer wire runs.
Working principle
The DHT11 works by combining a resistive humidity sensing element and a negative temperature coefficient (NTC) thermistor, both connected to an internal 8-bit microcontroller that processes and outputs the data digitally.
When the host microcontroller sends a start signal, the DHT11 wakes from low-power mode and transmits a 40-bit data packet containing both temperature and humidity readings:
- Bits 1–16: Relative humidity (integer + decimal)
- Bits 17–32: Temperature (integer + decimal)
- Bits 33–40: Checksum for data verification
For example, at 25°C and 60% RH, the sensor transmits: 00111100 00000000 00011001 00000000 01010101 — the last byte being the checksum (sum of the first four bytes).
Since the output is digital, no ADC is required. The microcontroller simply reads the serial data from the DATA pin and parses the values directly, reducing the chance of noise-induced errors compared to analog sensors.
Internal circuitry of the DHT11
Although the DHT11 looks like a compact 4-pin module, it contains several key components inside its package.
1. Resistive Humidity Sensor The primary humidity sensing element — a hygroscopic substrate between two electrodes that changes resistance with moisture levels in the air.
2. NTC Thermistor A negative temperature coefficient thermistor whose resistance decreases as temperature rises, allowing the internal MCU to derive an accurate temperature reading.
3. Internal 8-bit Microcontroller Reads both the humidity and temperature elements, performs analog-to-digital conversion internally, and packages the result into a 40-bit digital signal for output.
4. Calibration Memory (OTP) Factory-written one-time programmable memory that stores calibration coefficients, eliminating the need for external calibration in the field.
5. Single-Wire Interface Circuit Manages the proprietary serial communication protocol, handling the handshake timing and data transmission to the host microcontroller.
Specifications
| Parameter | Value |
|---|---|
| Supply Voltage | 3.3V – 5.5V |
| Supply Current | 2.5mA (measurement), 150µA (standby) |
| Temperature Range | 0°C to +50°C |
| Humidity Range | 20% to 80% RH |
| Temperature Accuracy | ±2°C |
| Humidity Accuracy | ±5% RH |
| Temperature Resolution | 1°C |
| Humidity Resolution | 1% RH |
| Sampling Rate | 1 Hz (once per second, maximum) |
| Response Time | 6–10 seconds (in still air) |
| Data Format | 40-bit serial (single-wire) |
| Pull-up Resistor | 4.7kΩ – 10kΩ (recommended) |
| Operating Temperature | 0°C to +50°C |
| Storage Temperature | -20°C to +60°C |
| Package Type | 4-pin SIP module |
| Output Impedance | Open-drain |
Interfacing projects
Download the datasheet: PDF here