Category: Instructional

Happy Pi Day! To celebrate π today, I am going to share how pi was used this past week in my robotics classes.

I was teaching students to use motor encoders with the LEGO EV3 robots. Previously we had been using the wait1Msec command to keep the motors running (pause and wait before moving on in the program) for a specific duration. This works, but requires a great deal of trial and error to complete tasks. Using the motor encoders allows the programmer to tell the motors how many rotations to make.

On the EV3 motors, there are 360 encoder counts for every revolution. That means there is an encoder count for every degree. This is where pi became important. Students measured the diameter of the wheel on the robot. Using the formula for finding circumference (C=D*π), students multiplied π * D to get C. This gave us the circumference of the wheel. We found the wheel to be about 2 1/8 or 2.125 inches. If you multiply 2.125 inches by π you get 6.67 inches. Students then divided the circumference by 360 to get the distance the robot would travel for every encoder count. We found this to be 0.0185 inches. So when a student wants the robot to travel a specific distance, let’s say two feet or twenty-four inches, they can mathematically calculate what encoder count to enter. All you have to do is take the desired distance and divide by 0.0185. That would give you the encoder count required to go the desired distance.

I led my students through this activity. I was pleased that I had integrated geometry in a real and relevant way. What I didn’t expect was what one group did to calculate the encoder count for a 90 degree turn. While most students used trial and error to find the encoder count that would make the 90 degree turn, one group decided to once again asked π for help. This group realized that when using a swing turn, the distance between the wheels would be the radius of a circle. So they multiplied the radius by 2 and multiplied by π to find the circumference of yet another circle. If you want to make a 90 turn, you just have to divide the circumference by 4 since 90 degrees is 1/4 of the circle. They took that distance and divided by the distance for each encoder count and you have the encoder count for a 90 turn.

This group found the distance between the wheels to be 4.75 inches. This doubled is 9.5 inches. Multiply 9.5 by π and you get 29.85 inches. Take 29.85 inches and divide by 0.0185 inches, the number found before, and you get 1613. Divide 1613 by 4 and you have the  encoder count needed to make a 90 degree turn. You end up around 403. We have found that there is some tweaking needed, but the calculations get you very close if not absolutely accurate.

We used the following code using ROBOTC.

//we used the motor sync because EV3 won’t go straight without syncing motors
//we have not started naming motors yet, so we used motorB and motorC
setMotorSyncEncoder(motorB, motorC, 50, 403, 25); //50 is the ratio for a swing turn, 403 is the encoder count and 25 is the motor power
waitUntilMotorStop(motorB);

That is true learning. These students used their knowledge of geometry to solve a real problem. This was one of those days that will remember for a very long time!

When I mention cloud computing to teachers I almost always get the deer-in-the-headlights look. It is the same look I would get when I started teaching adding fractions with unlike denominators to fourth graders.

So what is cloud computing? My very simple explanation is this. Cloud computing is when you are working on a website or mobile app that stores your information on a website. Basically the information you give the app isn’t on your computer, phone or iPad. It is on a web server somewhere.

So when we discuss using Dropbox or Google Apps, the files are not stored on your computer.

Why would you want to store your information or files on someone else’s server? The answer is access. If I save a file to my Dropbox, I have access to the file on almost any device anywhere I have an Internet connection.

In my district, the (local) desktop computers save our files on a school server. These files are only accessible when logged on to a school computer at one of our schools. If I want to take a file home to work on, I have to get it to another computer by emailing it to myself, saving to a USB drive, etc. Using a cloud drive like Dropbox, I save to the cloud folder and when I get home it is available on my home computer or iPad.

Keep in mind that if you are working on a file in a specific application such as Microsoft Word, you need to have an application that can open and edit the file to make changes. Also keep in mind that if you use a font that isn’t on both computers, the fonts will change.

Save to the cloud or not save to the cloud, that is the question! Only you can answer it.

If you have set a password or restriction code on your iPad, what happens if you forget what your password? If you set a password and turned on the erase feature, after 10 wrong attempts, the iPad erases the data. Even if you don’t set up the erase feature, you are still unable to use your device.

To reset your password or restriction code, follow these instructions from Apple. http://support.apple.com/kb/ht4097

Keep in mind you may loose some data and apps. You can reinstall your purchased apps from the app store.

A piece of advice… back up your iPad regularly.

If you have shelled out $500 or more for an iPad and another $50 or more for a case, you want to make sure your investment doesn’t grow legs and disappear. In the school environment, there are people in and put of my room all day. Although I lock things up when I am gone, there are times you must turn your back and walk away from your iPad.

The Find My iPad feature works through the iCloud system. Start by going to settings > iCloud. Turn on the Find my IPad feature. If you have not set up iCloud, it will prompt you to do this.

Once you have this set up, from your Mac or Windows computer, go to www.icloud.com. From there you will be prompted to log in with your Apple ID and password. You can see where your iPad is located, lock the screen and send a message to display on the screen. Even if you haven’t lost your iPad, it is fun to play with this feature. A final note, you will receive an email informing you that the Find My iPad feature was used.

Has this happened to you? You are typing away at your iPad only to find that several of your words are not even close to what you typed? It has happened to most of us.

My guess is that you have auto correction function turned on. Now I happen to like this feature. It does require me to go back and proofread what I wrote, but it saves me time in the long run.

To disable this feature, go to Settings > General > Keyboard and turn off Auto Correction. That should do the trick.