View source for DHT 11 Humidity & Temperature Sensor

== Introduction ==
[[File:DHT11 sensor module.jpg|300px]]

This DFRobot DHT11 Temperature & Humidity Sensor features a temperature & humidity sensor 
complex with a calibrated digital signal output. By using the exclusive digital-signal-acquisition 
technique  and  temperature  &  humidity  sensing  technology,  it  ensures  high  reliability  and 
excellent  long-term  stability.  This  sensor  includes  a  resistive-type  humidity  measurement 
component  and  an  NTC  temperature  measurement  component,  and  connects  to  a  high-
performance 8-bit microcontroller, offering excellent quality, fast response, anti-interference 
ability and cost-effectiveness.


== Technical Specifications: ==
[[File:Hdt11 specification.jpg|300px]]  


== Typical Application  ==
[[File:Dht11 application.jpg|300px]]

Note: 3Pin – Null; MCU = Micro-computer Unite or single chip Computer 
When the connecting cable is shorter than 20 metres, a 5K pull-up resistor is recommended; 
when the connecting cable is longer than 20 metres, choose a appropriate pull-up resistor as 
needed.


== Power and Pin  ==
DHT11’s power supply is 3-5.5V DC. When power is supplied to the sensor, do not send any 
instruction to the sensor in within one second in order to pass the unstable status. One 
capacitor valued 100nF can be added between VDD and GND for power filtering.  


== Communication Process: Serial Interface   ==
Single-bus  data  format  is  used  for  communication  and  synchronization  between  MCU  and 
DHT11 sensor. One communication process is about 4ms.  
Data consists of decimal and integral parts. A complete data transmission is  40bit, and the 
sensor sends higher data bit first.  
Data format: 8bit integral RH data + 8bit decimal RH data + 8bit integral T data + 8bit decimal T 
data + 8bit check sum. If the data transmission is right, the check-sum should be the last 8bit of 
"8bit integral RH data + 8bit decimal RH data + 8bit integral T data + 8bit decimal T data".