Here are the instructions to build a simple temperature logger using a $5.00 I2C temperature sensor. The data is stored to the SD card and can be easily imported into excel. Simply by changing or adding other sensors other types of data can also be collected.

The following components are used for this project:
Raspberry Pi(single board computer)
Temperature Sensor (SF-SEN-11931)

Solderless Breadboard
Hookup Wires

The Zagros Raspberry Pi 2 starter kit also includes everything needed for this project except the temperature sensor!

Step 1: Wire Up the Temperature Sensor

First, solder header pins or lead wires on to the sensor. We used headers so it would be could simply plug the sensor into a breadboard.

Make the following connections to the Raspberry Pi GPIO port. The ADD0 connection to ground determines the device I2C address. More than one sensor can be connected to the I2C bus, but they must each have a unique address.

Sensor RPi GPIO
VCC +3.3V

SDA SDA

SCL SCL

GND GND

ADD0 GND (note this sets the I2C device address)

ALT N/C

NOTE: DO NOT CONNECT THE SENSOR VCC TO +5VDC, THIS WILL DAMAGE THE SENSOR

Step 2: Enable the I2C Bus

*** Newer version may not require this step. If the file doesn't exist, move on to the next step.

First the I2C bus must be enabled.

There are two ways to enable the I2C bus.

The first and easiest is to do it with the raspi-config utility.

Use the command sudo raspi-config to start the utility.

Select Advanced Option to enabled the bus.

The second, but more complex way is to do it manually.

To do this, edit the configuration file /etc/modprobe.d/raspi-blacklist.conf

Use the command:

sudo nano /etc/modprobe.d/raspi-blacklist.conf

Now change the file contents from:

# blacklist spi and i2c by default (many users don't need them)

blacklist spi-bcm2708
blacklist i2c-bcm2708

To this:

# blacklist spi and i2c by default (many users don't need them)

blacklist spi-bcm2708
#blacklist i2c-bcm2708

Step 3: Update the Config.txt

Run the following command to update the config.txt

sudo nano /boot/config.txt

Add the following lines to the file:

dtparam=i2c1=on

dtparam=i2c_arm=on

Step 4: Set I2C Module to Load at Boot

The I2C module should be set to load when the Raspberry Pi starts up. Do this by editing the /etc/modules file.

The following command can be used to edit this file:

sudo nano /etc/modules

Add the following line to the end of the file:

i2c-bcm2708
i2c-dev

Step 5: Install I2C Packages

Install the i2c-tools and python-smbus packages to complete the I2C setup:

The following commands can be used to install the packages:

sudo apt-get install i2c-tools

sudo apt-get install python-smbus

Finally add the pi user (or whatever login required) to the I2C access group.

The following command can be used to accomplish this:

sudo adduser pi i2c

Use the following command to see what devices are connected to the I2C bus:

i2cdetect -y 1

Note: use the following command if you are using a model A Raspberry Pi

i2cdetect -y0

The I2C address (in hexadecimal) of the temperature sensor should show up if properly connected.

Step 6: Datalogger Program

Load and run the example program using the following command:

python temp_logger.py

The example program is very simple:

It reads the temperature from the temperature sensor every 60 seconds and logs it to a text file (Tempdata.txt)

temp_logger.py
Download

Step 7: Viewing Data

Use the following command to view the raw data file:

nano tempdata.txt

Copy the data to a USB drive and it can easily be imported in to Excel:

Step 8: Background Logging

To run the logger in the background (it will keep running after you log out). Use the following command:

sudo python temp_logger.py & ( Relative Path)
There are situations whereby the command above might give an error, such as Python: can't open file 'temp_logger.py': [Errno 2] no such file or directory

This simply means you will have to use an absolute path, which means you have to specify the location of the file from the root directory. An easy way to do this is to right-click on your temp_logger.py file, copy the path and paste in your terminal and then type "python" in front of it.

This is how my command looks;
python /home/pi/Desktop/temp_logger.py

Introduction: Raspberry Pi Temperature Logger