12 Mission Instructions

Earthquakes have puzzled humans throughout history. Scientists have worked hard to try to understand earthquakes so we can plan our cities in safer places, build stronger buildings, and prepare better when one is coming.

In order to study earthquakes, scientists use devices called seismographs to detect the motion of the Earth. A sensitive seismograph can record earthquakes so tiny that humans don’t even feel the motion. By recording many of these tiny tremors over time, scientists can try to understand when and why earthquakes occur and begin to make predictions about future earthquakes.

The first known seismographs come from China and date all the way to the first century. They didn’t use any electronics but were surprisingly efficient.

In this mission, you are a scientist developing a robotic seismograph that can travel to remote locations and measure tiny tremors. First, you will invent a way to simulate earthquakes so you can test your robot safely. Then you will design, test, and refine your robot until it is gathering the most useful data for you.

Your first design challenge in this mission is to decide how you will simulate earthquakes. Scientists simulate earthquakes all the time - to look at how different types of buildings will stand up to earthquakes, to test and calibrate earthquake detection equipment, and for other scientific studies.

The simplest type of earthquake simulator is an earthquake shaking table, or shake table. These tables provide a surface that can move in all directions. For this project, find a surface that you can easily shake back and forth (a small end table, for example), or you can build a real shake table that will more closely replicate an earthquake. Check out this resource about building your shake table.

Sketch a plan for your shake table on a piece of paper.

Set up your shake table, as you planned. Try it out - can your earthquake knock down a block building or house of cards?

Then, remove any extra sensors, outputs and attachments from your GoPiGo and attach your IMU sensor to the A1 or A2 port (GoPiGo3). Use zip ties or other means to keep your cords nice and neat.

Before you turn on your robot, plug in a USB drive in one of the four USB ports - you’ll need it for this mission.

Just like you’ve become an expert at installing sensors, you probably have a pretty good idea of how to use them as well. 

As usual, turn on your GoPiGo and connect to its Wi-Fi. Then type mygopigo.com into your browser. The first thing we are going to do is to test out our IMU sensor. If you need help, check out the IMU tutorial in the Learn in Bloxter section of DexterOS. Since we will also be using variables and lists, you need to go to Advanced Bloxter. 

Now, use the dropdown on the Sensor Control Panel to select the IMU sensor in the port it is plugged into AD1 or AD2 for the GoPiGo3.

The IMU sensor opens up a whole world of possible data to collect. 

At any time you want, you can see if your shake table is moving by looking at the Sensor Control Panel!

For this mission, you want to set your robot on your shake table and have it continuously checking for tremors, keeping track of the sensor readings over time. The IMU gives you lots of choices about how exactly you do that.

This is your twelfth GoBox mission, so you already know how to write a lot of different types of programs. What do you want your earthquake robot to detect? Our example code will use the IMU (accelerometer) but you might choose something different. That's ok!

You may remember creating your first list in Mission 8. As a reminder, a list is like a variable, but we can store more than one piece of data in it. Just like your shopping list, we can keep adding entries to our list, and we can go back and look at all the items on our list as well. If you would like to build your program to use the list function, you may do so, but we’ve got another idea.

For this GoBox Mission, we'll take lists to a whole new level by using the log function instead. Logging allows you to download a file with all the data from your robot so you can analyze it, graph it, and look for patterns yourself!

[BONUS: once you start to see some patterns, you can eventually teach your robot or your spreadsheet software to find the patterns for you. That's a version of programming too!]

Just like when we made our lists, you’ll need to set a variable for your robot to log.

Our example program will gather data from the IMU (accelerometer) in the Z-axis, but you can choose either X, Y, or Z. Don't worry too much about what all these different axes are. If your IMU is facing forward and pointing up like in our picture, then:

To log information, you’ll notice that we first named the file that will get downloaded onto our USB drive. We chose “log3” for our example, but you might name it “Earthquake1”. Definitely include a 1 at the end of your number, because every time you run your program, it will download a new file onto your USB drive, so we’ll change the name between every test. “Earthquake1”, “Earthquake2”, “Earthquake3”, etc. 

(The pictures we’re sharing are from our third attempt at solving this challenge - and I’ll let you in on a little secret. It took us more than three tries, but sometimes we forgot to update the name of our file in between tests! We’re all human!)

Let’s remember some of the basics we’ve learned over the past year:

SO - if we just add the command for the robot to Log “Z” in “sensor readings” (image 1), it will only do that one time, right at the beginning, and never do it again. That probably won’t be the most useful earthquake detector. 

You probably already guessed it, we’ll need to add in a loop. For our example code, we chose a time loop and randomly chose 2 minutes as our testing duration.

I don’t know about you, but just having the loop gave us waaaaay too many numbers to notice any patterns very easily. We are hoping for a robot that can alert us to when an earthquake is happening, not to live-stream even when the shake table is standing still. Time to add a conditional statement!

First, let’s take a look at the Sensor Control Panel while our robot is sitting still. What do you notice?

If you’re writing your code to measure the Z-axis like our example, then you might notice that a robot sitting totally still does not show a zero in the Z-axis!  This is because gravity is always pulling everything towards the center of the Earth (or, in our case, the ground). Gravity is a constant, and any accelerometer standing still on a flat surface will notice gravity tugging on it at a rate of 9.8 (m/s² is the unit, but don’t worry about that today).

THIS MEANS that the number that will trigger our earthquake detector needs to be designed around 9.8 instead of around 0! Run your looping program one time without any conditional statements.  Look for what the highest values are, and look for what the lowest values are.  What do you notice?

We noticed values as high as 15, and as low as 1.5 when our shake table was moving the most, but those were very extreme earthquakes. 

Let’s start with a pretty narrow range for what’s considered “not an earthquake”. I certainly don’t like it when I notice the ground moving in any amount, but maybe I’m just picky. 

You can choose how sensitive your robot is by adjusting the lower and higher values within your conditional statement.  Feel free to start with our samples, but you can change them at any time!

Now that you have a working seismograph, what will you do next? Will you modify your shake table to create a more realistic earthquake? Or will you change your program to record data more or less often?  Do you want your program to keep track of how many times motion was (or was not detected)? 

Can you use this robot in other situations, like detecting when someone is opening a drawer in your room? 

Follow the same steps – Design, Build, Code, Test – for each change you want to make. Make sure you keep track of your work.