Sensing for Science - Level 4 Data Loggers

Data loggers

We want to go out and collect data from the world. We could take our Arduino circuit and a laptop out to collect data, but that gets challenging with all the equipment and the fear of dropping your laptop. There is the current trend of using IoT (Internet of Things) to send data via the internet, which works great when there is good internet. Out here in Montana, internet connection is not guaranteed. So we will save data locally but using a data logger SD card module. This device will allows us to save data to a micro sd card for us to pull later.
This material is based upon work supported in part by the National Science Founda-tion EPSCoR Cooperative Agreement OIA-1757351. Any opinions, findings, and conclu-sions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Circuit #1

Let’s start with testing the module and the SD card. Wire up the following circuit . CS->4, SCK->131, Mosi->11, Miso->12

Once you have the SD card module wired up, we can write some code to test the circuit. Copy the code and upload it to the Arduino board. This code is also under examples in the SD card library.

Upload the code to the Arduino board and open the serial monitor. If everything is working correctly, you should see the results shown below. If you get an error message you might have to reformate your SD card (see formatting steps in the instruction video) or your SD card is damaged.
If you have an successful test you should be able to pull the SD card and open the file on the pc. It will should up as a .txt file.

Circuit #2 

This next circuit we are going to build will collect temperature data for us at a set interval of time (roughly 10 seconds). This circuit is great when you need to step away but need continuous data collection. You will need a the TMP36, LCD (with I2C), and the data logger. Most of the circuit you will recognize as it is the same temperature sensor from the previous level.

Once you have the circuit built, we can move onto the code. You will notice that the code is starting to get pretty complex. I will break down sections of the code that are new to this project. 

When you have the code ready and uploaded, the circuit will start working right away. You should see the circuit go through its setup code. If everything is ready you should see something like in the image below.

After the setup, the circuit will take a temperature reading and will display on the LCD.

The circuit will save the data to a SD card and you will get a messaging them us that the information was successfully saved.

After we wait for awhile we can turn off the circuit and pull the SD card. Using a SD card we can plug in the pc and open up the drive. You should see a data log file as .txt file. We can open it and see our data.
Here is an example of the code in the notepad app. You can import this info into excel to better analyze the date.

What are some down falls of the code we created? How can we improve this code to get us more reliable data?

Circuit #3

Now that we have creating a data logger, lets create a circuit that will only collect data when we want it to by pushing a button. We can keep everything from the previous circuit connected. We will just add the button to the design.

This setup will make the Arduino sense a button push. When the button is not being pushed it sits in the “HIGH” status. When pushed current runs through the onboard resistor and sets the status as “LOW”. We will use that to trigger the saving of our data. Here is the new code for our circuit.