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1. PI ARDUINO I2C EXAMPLE TWO WAY DATA WIRINGPI INSTALL
2. PI ARDUINO I2C EXAMPLE TWO WAY DATA WIRINGPI UPDATE

But with both these sensors costing <$5 you can probably afford to buy both and experiment.In the third installment of the I2C series, I will show you two ways to interface a 3.3-volt Raspberry Pi with a 5-volt Arduino Uno. A weather station would be an idea project but a central heating controller may require something different.įor projects that need a faster temperature reading rate (<2 sec) I would probably use a DS18B20 as they respond much faster to changes in temperature. The DHT11 is probably best suited for projects where rapid data readings are not required and the environment is not expected to see sudden changes in temperature or humidity. Some may only sell the device itself so you may need to shop around if you would prefer the 3-pin module. The DHT11 is available from many electrical component sellers. This script can be downloaded directly to your Pi using : wget Īnd run using : python dht11.py Buying a DHT11 Print('Temp=%'.format(temperature, humidity)) If humidity is not None and temperature is not None: # the Pi might fail to get a valid reading. # Reading the DHT11 is very sensitive to timings and occasionally Humidity, temperature = Adafruit_DHT.read_retry(sensor, gpio) # get a sensor reading (waiting 2 seconds between each retry). # Set sensor type : Options are DHT11,DHT22 or AM2302 Simply import the module, setup a few variables and call the “read_retry” function : Once the Adafruit library is installed and you’ve got the example script to work you can use the sensor in your own scripts. You should see an output similar to this : Temp=22.0* Humidity=68.0% Using the Library In Other Python Scripts You can change this if you are using a different GPIO pin for your data/out wire. The second is the GPIO number so for my example I am using “17” for GPIO17. The first is the sensor type so is set to “11” to represent the DHT11. Adafruit Example Python ScriptĪdafruit provide an example script that you can use to check your sensor is operating correctly. Hopefully at this point the library is installed and ready to be used within a Python script.

PI ARDUINO I2C EXAMPLE TWO WAY DATA WIRINGPI INSTALL

Then install the library for Python 2 and Python 3 : sudo python setup. Then clone the Adafruit library from their repository : git clone https : ///adafruit/Adafruit_Python_DHT.git Sudo apt - get install build -essential python -dev

PI ARDUINO I2C EXAMPLE TWO WAY DATA WIRINGPI UPDATE

To start with update your package lists and install a few Python libraries : sudo apt - get update The Pi’s operating system may get in the way while performing other tasks so to compensate for this the library requests a number of readings from the device until it gets one that is valid. The library deals with the data that needs to be exchanged with the sensor but it is sensitive to timing issues.

In order to save time trying to implement this yourself it’s far easier to use the Adafruit DHT library. The DHT11 requires a specific protocol to be applied to the data pin. It has a 10K resistor between pin 1 (3.3V) and 2 (Data/Out). Here is a 4-pin sensor connected to the Pi’s GPIO header. In my example I am using physical pin 11 which is GPIO 17. Your data pin can be attached to any GPIO pin you prefer. The 3 pins should be connected to the Pi as shown in the table below : DHT Pin For this reason I got hold of the module which I could then attach to the Pi with a piece of 3-way Dupont cable.ĭifferent suppliers may wire the module pins differently so check the PCB markings to identify Vcc (+), data and Ground (-). The 3-pin modules will usually have this resistor included which makes the wiring a bit easier. The 4-pin device will require a resistor (4.7K-10K) to be placed between Pin 1 (3.3V) and Pin 2 (Data). If you do you may get incorrect readings. The manufacturers do not recommended that you read data from this device more than once per 2 seconds. The modules have three pins and are easy to connect directly to the Pi’s GPIO header.

You can buy the 4-pin device on its own or as part of a 3-pin module. The device itself has four pins but one of these is not used. The device only requires three connections to the Pi. It isn’t the fastest sensor around but its cheap price makes it useful for experimenting or projects where you don’t require new readings multiple times a second. The DHT11 is a low-cost temperature and humidity sensor.