DS18b20 and the Raspberry PI example

In this example we connect a DS18b20 temperature sensor to our Raspberry PI and read in the value, here is the schematic for this.

pi and ds18b20

Start the terminal and entering the following

[codesyntax lang=”bash”]

sudo modprobe w1-gpio

sudo modprobe w1-therm

cd /sys/bus/w1/devices
ls

cd 28-xxxxxxxxxx (change this to match the serial number that pops up)

cat w1_slave

[/codesyntax]

You should see something like this

terminal_ds18b20

In the output above the t=18875 is the temperature, in this case this is equal to 18.875

Now we will try this in python

Open the terminal and type in the following

[codesyntax lang=”bash”]

sudo idle

[/codesyntax]

Wait for IDLE to open,  then click File > New to open a new window. Or you can use CTRL + N.

Now type in the following code

[codesyntax lang=”python”]

import time

while 1:
 tempfile = open("/sys/bus/w1/devices/28-0000027a4334/w1_slave")
 temptext = tempfile.read();
 tempfile.close()
 tempdata = temptext.split("\n")[1].split(" ")[9]
 temperature = float(tempdata[2:])
 temperature = temperature / 1000
 print temperature
 
 time.sleep(1)

[/codesyntax]

Click File > Save when you are finished (Ctrl + S).

To run your program, click Run > Run (Ctrl + F5), your should output like the following

ds18b20_out