DHT11(Temperature Humidity Sensor) | Code | Circuit

DHT11 

DHT11 has a highly calibrated digital signal output pin of the temperature and humidity combined sensor (no analog input pins needed). It uses dedicated digital modules, capture technology, and temperature and humidity sensor technology to make that product with high reliability and excellent long-term stability. This sensor module includes a resistivity element and an NTC temperature module the measurement device and connected to any high-performance microcontroller as an input device.

 DHT11- Digital Temperature and Humidity sensor.

 Model num: DHT11

Other related devices: DHT22,HR-202, AM2302, SHT71,AMT1001.

Other names: Humidity sensor, temperature sensor

DHT11-Temperature & Humidity

It is good to use but the user has careful timing to grab the data. The only thing about this sensor is the user can only get new data every 2 seconds. So when using this sensor, readings can be up to 2 seconds old.

Compared to the DHT22, it is less precise, less accurate, and works in a smaller range of temperature/humidity readings, but it's smaller and less expensive.

DATASHEET: DOWNLOAD

• LCD- Interface
• Temperature Sensor-Interface

Pin description

1	Vcc	Power
2	D0	Data_pin(serial-data, single bus)
3	NC(X)	No Connection
4	GND	Ground

Specifications

Relative Humidity

Resolution	16Bit
Repeatability	±1%RH
Accuracy	25℃±5%RH
Interchangeability	Fully-interchangeable
Response time	1/e(63%)25℃6s 1m/s Air 6s
Hysteresis	<±0.3%RH
Long-term stability	<±0.5%RH/yr
Range	20% - 80% in air

Temperature

Resolution	16Bit
Repeatability	±1℃
Accuracy	25℃±2℃
Response time	1/e (63%) 10S
Range	0 ͦ C – 50 ͦ C

DHT-Sensor vs. DHT-Module

DHT11 module Comes with a 4.7K or 10K resistor, which you  want to use it as a pull-up from the data pin to VCC.

So, the difference between the Module and DHT sensor is that module has a little circuitry includes a pull-up resistor or 5.5k resistor and the capacitor filter is connected to the data pin and Vcc.

Data sequence: How to Read data?

Single Bus Description

DHT11 device uses simplified single-bus data communication. A single bus that has only one data line, the data exchange system is controlled by a single bus is complete, a single bus usually requires an external approximately 5.1kΩ or 10kohm pull-up resistor, so that when the bus is idle, the state is high. Because they are the master-slave structure, only the host calls a slave, a slave to answer, so the host access. Devices must strictly follow the data sequence of a single bus, if there is any problem in the data sequence, the device will not respond to the host.

 

Single bus data transfer bit definition:

DATA sequence format is used for communication between the microcontroller and DHT11 for synchronization, single-bus data format, a 40-bit data transfer, high first-out.

 

Data formats:

8bit humidity-integer data + 8bit decimal data +8 bit temperature and humidity data + 8bit temperature-decimal integer data +8 bit parity bit.

 

Parity bit data definition

"8bit humidity decimal integer data + 8bit humidity temperature data + 8 bit decimal integer
data + 8bit temperature data"  8bit the parity bit is equal to the result of the end of eight.

Example one： 40-bit data receive

00110101     0000 0000     00011000      00000000    01001101

00110101- High humidity(8-bit)  

00000000 - Low humidity(8-bit data)

00011000 - High temperature(8-bit data)

00000000 - Low-temperature(8-bit data)  

01001101 - Parity bit

Calculated as follows:

00110101 + 00000000 + 0001 1000 + 0000 0000 = 01001101

So 01001101 = 01001101 Receive data is correct

Humidity: 00110101=35H=53%RH.

Temperature: 00011000=18H=24℃.

Example Two: The received data is 40

0011 0101     0000 0000    0001 1000   0000 0000     0100 1001

0011 0101 - High humidity(8-bit)

0000 0000 - Low humidity(8-bit)

0001 1000 - High temperature(8-bit)  

0000 0000 - Low temperature(8-bit)  

0100 1001 - Parity bit

Calculated as follows:
0011 0101+0000 0000+0001 1000+0000 0000＝ 0100 1101

01001001 is not equal to 01001101

The received data is not correct, give up, again receiving data.

DHT11-Interface with Arduino

Circuit diagram

DHT11 Temparature Humidity

Arduino code with DHT11: DOWNLOAD

/***************************************************** # DHT11 Example sketch follow us: www.technoelectronics44.com ******************************************************/ #include<SoftwareSerial.h> #include<dht.h> #define DHT11_PIN 8 dht DHT; void setup() { Serial.begin(9600); Serial.print("WELCOME TO TECHNOELECTRONICS:"); Serial.println(); } void loop() { DHT.read11(DHT11_PIN); Serial.print("TEMPARATURE:"); Serial.println(DHT.temperature); Serial.print("HUMIDITY:"); Serial.println(DHT.humidity); delay(1000); }

 Timing Diagram:

DHT1 Timing Diagrams

DATASHEET

Product Highlights

• Low-cost
• long-term stability
• relative humidity and temperature measurement
• excellent quality
• fast response
• anti-interference ability
• long-distance signal transmission
• precise calibration

Applications

• automotive, automation
• data loggers
• weather stations
• home appliances
• humidity regulator
• medical and other
• relevant humidity measurement and control

Related Topics

Arduino

LCD-interface

Temperature Sensor-Interface

ULTRASONIC SENSOR

LDR