The microcontroller which is connected to the DHT11 sensor sends the start signal to the DHT11 sensorwhich activates the sensor. The complete data consists of total eighty bits and the DHT11 sensor is programmed to deliver HIGHER bit first. Data provided by the DHT11 sensor consists of two parts 1) Decimal part and 2) Integral part. This format in which the DHT11 temperature and humidity sensor transfers the data is called the 1-wire format or single data bus format. It is important to note here that the DHT11 sensor provides the digital data following a particular protocol. As we learned in the previous section that the DHT11 temperature and humidity sensor is the digital sensor which means that this sensor provides the data at its output terminal in the digital format. In this we will see how the DHT11 sensor transfers its data to the microcontroller. The DHT11 sensor looks like the one in the following image: The detailed discussion on the data transmission from the DHT11 sensor to the microcontroller will be done in the following section. The data that is the reading of the temperature and humidity is provided over the single terminal called the Data bus. The DHT11 temperature and humidity sensor measures temperature using NTC (Negative temperature measurement co-efficient) temperature measurement component and on the other measures humidity using resistive-type humidity measurement component. The DHT11 sensor is digital that is provides data in digital form it is opposite to thermistor whose values for temperature measurement are analog in nature. It is important to note here that this sensor measures both the temperature and humidity simultaneously that is on each request for data from the microcontroller the DHT11 sensor generates the data packets containing the information about both the temperature and humidity.
Before diving deep into the discussion on the interfacing of the Arduino microcontroller development board and DHT11 sensor let us first what the DHT11 sensor is? DHT11 sensor is used to measure the temperature and humidity of the surroundings in which it is installed.
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