Ⅰ.Introduction to DHT11

DHT11 digital temperature and humidity sensor is a temperature and humidity composite sensor with calibrated digital signal output. It applies dedicated digital module acquisition technology and temperature and humidity sensing technology to ensure that the product has extremely high reliability and excellent long-term stability. The sensor includes a resistive humidity sensing element and an NTC temperature measuring element, and is connected to a high-performance 8-bit microcontroller. Therefore, this product has the advantages of excellent quality, ultra-fast response, strong anti-interference ability, and extremely cost-effective.

Each DHT11 sensor is calibrated in a very accurate humidity calibration chamber. The correction factors are stored in the OTP memory and are converted into the OTP memory when the detected signal is converted. The single-wire serial communication method simplifies system integration. It is small in size, consumes very little power, and can transmit signals within a range of 20 meters, which makes it an ideal choice in various application fields.

DHT11 is a temperature and humidity sensor with calibrated digital signal output. Its precision humidity is ±5%RH, temperature is ±2℃, measuring range humidity is 5~95%RH, and temperature is -20~+60℃.

Ⅱ.Specifications of DHT11

•Product Category:Temperature Sensor Development Tools
•Type:Humidity,Temperature Sensor
•Package:Blister Pack
•Working voltage:3.5V~5.5V
•Working current:0.3mA~60uA
•Tool used for evaluation:DHT11
•Working power supply voltage:5V
•Minimum operating temperature:0℃
•Maximum operating temperature:+55℃
•Humidity measurement range:20%~90%
•Temperature resolution:0.1℃
•Humidity resolution:1%
•Accuracy:±2℃ and ±5%

Ⅲ.DHT11 pin description

•Pin1(VDD):Power supply 3-5.5V
•Pin2(GND):Ground, negative pole of power supply
•Pin3(DATA):Serial data, single bus
•Pin4(NC):No pin, please leave it in the air

Ⅳ.Working principle of DHT11

1.Humidity sensitive element: The humidity sensitive element contained inside DHT11 is a capacitive humidity sensor. When this component is exposed to air, changes in moisture cause changes in capacitance. This change can be converted into an electrical signal to measure the humidity in the air. The working principle of the capacitive humidity sensor is based on the principle that the presence of water molecules in the air affects the capacitance. When the moisture content in the air increases, the dielectric constant of the sensing capacitance will increase, thereby changing the value of the capacitance. . By measuring changes in capacitance, the level of humidity in the air can be determined.

2.Measurement process: The sensor obtains the humidity and temperature values of the current environment by measuring the capacitance change of the humidity sensitive element and the resistance or voltage change of the temperature sensitive element.

3.Temperature sensitive element: DHT11 also contains a temperature sensitive element, usually a thermistor or thermocouple. Changes in temperature will cause the resistance or voltage value of this component to change. The thermistor is a temperature sensor that uses the resistance of a semiconductor to change with temperature. When the temperature changes, the resistance value of the thermistor changes, allowing the temperature to be measured. The temperature sensitive element in the DHT11 sensor can measure the temperature in the air and output the temperature data together with the humidity data to provide a complete temperature and humidity measurement function. Such combined sensors are useful in many applications, such as in devices in areas such as smart homes, environmental monitoring, and agriculture.

4.Signal processing: The circuit inside the sensor processes changes in humidity and temperature and outputs the results in the form of digital signals. This digital signal is usually transmitted in a specific data format, for example, binary data over a single bus.

5.Digital output: A microcontroller or other digital device can read the digital signals output by the sensor and obtain the temperature and humidity values of the environment by analyzing these signals.

Ⅴ.Detailed Specifications of DHT11

Ⅵ.Electrical Characteristics of DHT11
VDD=5V,T=25℃(unless otherwise stated)

Ⅶ.Steps to correctly connect DHT11 to microcontroller or other devices

1.Understand the DHT11 pins: DHT11 usually has four pins, including VCC, GND, DATA and an NC. Make sure you understand the function of each pin correctly.

2.Data connection: Connect the DHT11's DATA pin to the digital input pin of a microcontroller or other device. This is the pin used by the sensor to send temperature and humidity data.

3.Power supply connection: Connect the VCC pin of the DHT11 to the power pin of the microcontroller or other device, usually 3.3V or 5V. At the same time, connect the GND pin to the corresponding ground pin.

4.Pull-up resistor: Add a 4.7k ohm to 10k ohm pull-up resistor on the DATA pin. This helps ensure signal stability during transmission.

5.Connect the unused pin (NC): Although the NC pin is unused, it is recommended to connect it to ground (GND) to ensure the stability of the sensor.

Ⅷ.Application scenarios of DHT11

1.Meteorological observation: DHT11 can be used to observe meteorological data, including temperature and humidity, which is very important for weather forecasting, climate change research, etc.

2.Temperature and humidity monitoring: DHT11 can be used to monitor the temperature and humidity in the environment. It is very useful in many fields. For example, in industries such as agriculture, animal husbandry, and manufacturing, the requirements for environmental temperature and humidity are relatively high. DHT11 Temperature and humidity data in the environment can be monitored in real time to help these industries maintain a comfortable living and working environment and take timely adjustment measures.

3.Medical field: In the medical field, DHT11 can also be used to monitor temperature and humidity data in important places such as wards and operating rooms to ensure that the temperature and humidity environment in these places can meet the needs of medical work.

4.Air quality detection: DHT11 can be used to detect indoor air quality. By monitoring changes in indoor temperature and humidity in real time, it can help us judge the quality of indoor air and take appropriate measures.

5.Smart home: DHT11 can be used in smart home systems. Smart home systems need to monitor indoor temperature and humidity data in real time to achieve more intelligent home environment control.

6.Electronic equipment heat dissipation monitoring: DHT11 sensor can be used to monitor the heat dissipation of electronic equipment. In some applications that need to monitor the temperature of electronic devices, DHT11 can be used to detect the temperature of the environment around the device to help adjust the cooling system. For example, in electronic devices, if there is a problem with the cooling system, it may cause the device to overheat, thus affecting the device performance and lifespan. By using the DHT11 sensor to monitor the temperature of the environment around the equipment, overheating of the equipment can be detected in time, and measures can be taken to adjust the cooling system in a timely manner to ensure the normal operation of the equipment.

7.Internet of Things projects: As a common sensor, DHT11 is widely used in various Internet of Things projects because it is easy to integrate into microcontrollers and microcontrollers. In smart home systems, DHT11 can be used to measure and monitor indoors temperature and humidity. By connecting with a microcontroller or microcontroller,

DHT11 can read the temperature and humidity values ​​in the environment and send these data to a central controller or cloud server through a wireless network or wired network. In this way, users can access the data through a mobile phone application or smart phone. Devices such as speakers remotely control devices in your home and adjust accordingly based on environmental conditions.

8.Food storage environment monitoring: Maintaining appropriate temperature and humidity during food storage and transportation is crucial to maintaining the freshness and quality of food. The DHT11 sensor can be used to monitor temperature and humidity in food storage environments. By placing the DHT11 sensor in the food storage environment, it can regularly read the current temperature and humidity values. These data can be used to monitor environmental conditions in real time to ensure that the food is in the best storage condition. For temperature monitoring, DHT11 can detect storage Temperature changes in the environment help detect abnormalities in time.

For example, if the temperature is too high or too low, the DHT11 will send an alarm signal to remind managers to take steps to adjust the ambient temperature. For humidity monitoring, the DHT11 can detect the humidity level in the storage environment. Humidity is crucial for food preservation because too high a humidity can lead to the growth of pathogens, while too low a humidity can cause food to dry out. By monitoring humidity, you can ensure your food is at the proper moisture level, extending its shelf life.

Ⅸ.Basic information of DHT11 output data

1.Data format: The first two bytes in the data frame represent the humidity value, the middle two bytes represent the temperature value, and the last byte is the checksum.

2.Frame structure: DHT11 outputs a 40-bit data frame for each measurement. This 40-bit data is divided into 5 bytes, each byte is 8 bits.

3.Temperature data: Temperature data occupies the middle two bytes of the data frame, with the same high bit in front and low bit in the back. These two bytes of data represent the temperature value in degrees Celsius.

4.Humidity data: Humidity data occupies the first two bytes of the data frame, with the high bit in front and the low bit in the back. These two bytes of data represent the relative humidity value in percentage.

5.Checksum: The last byte of the data frame is the checksum, which is used to verify the integrity of the previous data. The checksum is the sum of the high bits of the humidity data, the low bits of the humidity data, the high bits of the temperature data and the low bits of the temperature data.

X.Common DHT11 usage issues

1.Power supply problem
•Unstable power supply voltage: Unstable power supply voltage may cause abnormal operation of DHT11. Make sure the power supply voltage is stable.

2.Hardware connection problem
•Power supply issues: Make sure you are providing the correct supply voltage to the DHT11, usually 3.3V or 5V.
•Pin connection error: Check whether the pin connection of DHT11 is correct, including the correct connection of power, ground, data and other pins.

3.Program code issues
•Pin configuration errors: Make sure the pins specified in the program code match the actual connected DHT11 pins.
•Incorrect code implementation: Check whether the program code used correctly implements the DHT11 reading and parsing process. Make sure the delays, checksum calculations, etc. in the code are correct.

4.Environmental conditions
•Extreme environments: DHT11 is suitable for general indoor use, but under extreme environmental conditions, such as extremely high or low temperatures and humidity, it may cause performance problems.

5.Line interference
•Electrical noise: Strong electrical components may introduce electrical noise, affecting the performance of DHT11. Isolate DHT11 from strong electrical components, or take other measures to reduce electrical interference.

6.Measurement frequency
•Frequent measurements: Too frequent measurements may cause DHT11 performance degradation. Make sure the measurement frequency is within the range required by the sensor specifications.

7.Sensor damaged
•Physical damage: Check the DHT11 for physical damage, such as bent or damaged pins.

Frequently Asked Questions

1.What are the limitations of DHT11?
The only real downside of this sensor is that you can only get new data from it once every 2 seconds. The DHT11 module works on serial communication is single wire communication.

2.How accurate is the measurement of DHT11?
DHT11 is a low-cost temperature and humidity sensor with relatively low measurement accuracy. Usually under normal use conditions, the accuracy of humidity is ±5% relative humidity and the accuracy of temperature is ±2 degrees Celsius. This means that the sensor's measurement results may be within plus or minus 5% of the actual value and plus or minus 2 degrees Celsius.

3.Is DHT11 analog or digital?
The DHT11 is a basic, ultra low-cost digital temperature and humidity sensor. It uses a capacitive sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed).

4.Is DHT11 a thermostor?
DHT11 is a basic and low-cost digital temperature and humidity sensor, using a capacitive humidity sensor and a thermistor to measure the surrounding air.