DHT11 Temperature/Humidity Symbol
Definition: The DHT11 Temperature/Humidity symbol represents a low-cost digital sensor module that measures ambient temperature (0–50 °C) and relative humidity (20–90 % RH) and transmits calibrated readings as a serial digital signal on a single-wire data bus, shown in schematics as a three-terminal functional block with VCC, DATA, and GND pins.
Also known as: DHT11, DHT11 sensor, temperature humidity sensor, digital temperature sensor, RHT sensor.
What the DHT11 Temperature/Humidity symbol means
The DHT11 symbol denotes a capacitive humidity sensor combined with a thermistor temperature sensor on a single module, with an internal 8-bit microcontroller that performs analogue-to-digital conversion and transmits calibrated 40-bit data packets over a proprietary single-wire protocol. The sensor is widely used in hobbyist, educational, and low-cost IoT projects for environmental monitoring.
In a circuit diagram the DHT11 symbol marks a sensor node that outputs pre-calibrated temperature and humidity data. Because the output is digital (not analogue), no ADC is needed in the host microcontroller; the host simply reads the serial data stream and interprets the 40-bit packet directly as temperature and humidity values.
How to identify the DHT11 Temperature/Humidity symbol
The DHT11 symbol is a labelled rectangular functional block inscribed 'DHT11' or 'Temp/Humidity'. Three pins are shown: VCC (3.3–5 V power supply, top or right), DATA (single-wire digital serial output, centre), and GND (ground, bottom or left). In actual schematics the DATA pin is shown connected through a 10 kΩ pull-up resistor to VCC, which is required for correct single-wire bus operation.
Function in a circuit
The DHT11 contains a resistive-type humidity sensing element and an NTC thermistor. The internal ADC converts both analogue sensor signals to digital values. On each measurement cycle (triggered by the host pulling DATA low for ≥18 ms), the DHT11 transmits a 40-bit serial packet: 8-bit humidity integer, 8-bit humidity decimal (always 0 for DHT11), 8-bit temperature integer, 8-bit temperature decimal (always 0 for DHT11), and 8-bit checksum. Temperature accuracy is ±2 °C; humidity accuracy is ±5 % RH.
Standards: IEC vs ANSI
| IEC 60617 | There is no specific IEC 60617 symbol for the DHT11 sensor. It is represented as a generic functional block per IEC 60617-02 conventions, labelled with the device name. |
|---|---|
| ANSI/IEEE 315 | IEEE 315 / ANSI Y32.2 treats the DHT11 as a labelled functional module block. No unique standardised glyph exists for proprietary sensor modules. |
| Key difference | Both IEC and ANSI/IEEE represent the DHT11 as a generic labelled rectangle. The device-specific information is conveyed by the component label and pin annotations, not by a standardised glyph. |
Terminals / pins
| Pin | Name |
|---|---|
| vcc | VCC |
| data | DATA |
| gnd | GND |
Typical values
Temperature range: 0–50 °C, accuracy ±2 °C, resolution 1 °C. Humidity range: 20–90 % RH, accuracy ±5 % RH, resolution 1 % RH. Supply voltage: 3.3–5.5 V DC. Supply current: 0.3 mA (measuring), 60 µA (standby). Data protocol: single-wire proprietary. Sampling period: minimum 1 second between readings. Package: 4-pin single-row (pin 1: VCC, pin 2: DATA, pin 3: NC, pin 4: GND) or 3-pin module.
Where the DHT11 Temperature/Humidity symbol is used
- Home automation systems monitoring indoor temperature and humidity for HVAC control.
- Arduino and Raspberry Pi weather station projects logging climate data to the cloud.
- Greenhouse monitoring systems triggering ventilation or misting when humidity thresholds are exceeded.
- Server room environment monitoring alerting staff to temperature or humidity anomalies.
- Educational electronics kits introducing students to digital sensor protocols on microcontrollers.
- Low-cost IoT nodes reporting environmental data via Wi-Fi (ESP8266/ESP32) to MQTT brokers.
Example
In an Arduino Uno weather station, the DHT11 symbol shows VCC connected to the Arduino 5 V rail, GND to GND, and DATA connected through a 10 kΩ pull-up resistor to 5 V and then to Arduino digital pin 2. The Arduino sketch uses the DHT library to trigger a measurement every 2 seconds, decode the 40-bit packet, and print temperature and humidity to a 16×2 LCD display.
Key facts
- The DHT11 sensor measures temperature (0–50 °C, ±2 °C accuracy) and relative humidity (20–90 % RH, ±5 % RH accuracy) and outputs calibrated digital data on a single-wire bus.
- The three schematic pins are VCC (3.3–5 V supply), DATA (single-wire serial data with pull-up resistor required), and GND.
- A 10 kΩ pull-up resistor from the DATA pin to VCC is required for reliable single-wire bus operation; without it, the bus may float and produce incorrect readings.
- The DHT11 transmits a 40-bit data packet on each measurement: 8-bit humidity integer + 8-bit humidity decimal + 8-bit temperature integer + 8-bit temperature decimal + 8-bit checksum.
- Minimum sampling interval is 1 second (1 Hz); attempting to read faster than 1 Hz causes the DHT11 to return stale data or communication errors.
- The DHT22 (AM2302) is the higher-accuracy upgrade: temperature range −40 to +80 °C (±0.5 °C accuracy) and humidity range 0–100 % RH (±2–5 % RH), with the same three-pin single-wire interface.
- The DHT11 uses no external standard (IEC 60617 or IEEE 315) unique symbol; it is represented in schematics as a generic labelled functional block.
Frequently asked questions
What does the DHT11 sensor symbol look like in a circuit diagram?
The DHT11 symbol is a labelled rectangle inscribed 'DHT11' with three pins: VCC (power supply), DATA (single-wire serial output), and GND. In most schematics a 10 kΩ resistor is shown connected between the DATA pin and VCC as the required pull-up.
What does the DHT11 sensor measure?
The DHT11 measures ambient temperature in the range 0–50 °C with ±2 °C accuracy and relative humidity in the range 20–90 % RH with ±5 % RH accuracy. Both measurements are output as 8-bit integer values in a 40-bit serial data packet.
What pins does the DHT11 have?
The DHT11 has three active pins: VCC (3.3–5.5 V supply), DATA (single-wire digital serial output), and GND. The bare 4-pin IC version has an additional unused pin (pin 3, NC—no connection). Most pre-built modules expose only the three active pins with a built-in pull-up resistor.
Why does the DHT11 DATA pin need a pull-up resistor?
The DHT11 uses an open-drain single-wire bus protocol: both the host microcontroller and the sensor drive the data line low, and the pull-up resistor (10 kΩ) pulls the line high when neither device is actively pulling it low. Without the pull-up the bus floats high-impedance and the communication fails.
What is the difference between the DHT11 and DHT22?
The DHT22 (AM2302) has better accuracy (±0.5 °C temperature, ±2–5 % RH humidity), a wider range (−40 to +80 °C, 0–100 % RH), and higher resolution (0.1 °C, 0.1 % RH) compared to the DHT11's 1 °C and 1 % RH resolution. Both use the same three-pin single-wire protocol and can be used with the same software libraries, but the DHT22 costs slightly more.
How often can I read data from the DHT11?
The DHT11 requires a minimum of 1 second (1 Hz) between successive measurements. Reading more frequently causes the sensor to return a cached previous reading or generate a communication error. For higher sampling rates, the DHT22 or a professional I²C sensor (e.g. SHT31) should be used instead.
Which microcontrollers are compatible with the DHT11?
The DHT11 is compatible with any microcontroller that has a digital I/O pin capable of bit-banging the proprietary single-wire protocol, including Arduino (all variants), ESP8266, ESP32, Raspberry Pi, STM32, and PIC microcontrollers. Popular software libraries (Arduino DHT library, MicroPython dht module) handle the protocol timing automatically.
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