# Monthly Archives: March 2014

teaching

## Basic Logic for Linear Algebra

This Tuesday in class, we will talk about basic logic and the field axioms. Since these topics aren’t explicitly covered in the text for the class, I wrote up some supplemental notes. You can download these notes here. As usual, let me know in the comments below if anything is incorrect or unclear. The “exercises” in the essay are just for your own edification — you will certainly not be asked to submit solutions!

teaching

## Welcome to Math 115AH

This post is just an announcement welcoming my students to Math 115AH (linear algebra) this quarter. I am super excited to be working on this course! I am tentatively planning on holding office hours for the course on Tuesday and Thursday after class (12 – 1) in my office, MS 3915B.

You can find Professor Gieseker’s course website here.

I will occasionally post material relevant to class on my blog. Entries (such as this one) will be tagged M115AH.

musings

## Now I can recommence my weekend plans

The perfectly addictive mobile game has the right balance of conceptual simplicity, strategy and randomness. 2048 hits this balance perfectly.

computing

## Building a Photo Booth: Part I

As a project for a certain event this summer, I’ve decided to try my hand at building a photo booth. Like a traditional photo booth, my photo booth should take several pictures separated by a few seconds, then print the photos. Additionally, I think it would be neat to also post the pictures automatically to some social media like twitter or instagram. After doing some research, I found that my best option for building such a photo booth was to use a Raspberry pi (Rpi) along with the optional camera attachment. Together, the Rpi and the camera cost around $70. To print the pictures, I bought a used photo printer (an Epson PictureMate) off of ebay for another$35.

Setting up the Rpi The Rpi is meant to be very easy to set up. However, my setup was a bit complicated by the fact that I didn’t want to buy an external keyboard and monitor for my pi. Fortunately, I found some tutorials for setting up the computer over my wireless network. The first step is to format the SD card with the operating system for the Rpi. I followed the instructions here. Once the SD card was formatted, I followed the instructions here to set up my pi over my local network. Finding the IP address of my pi on the network proved to be a bit of trouble. I ended up downloading a tool called LanScan which easily found the IP address for me.

Once my pi is turned on and plugged into my router, I can now log in via ssh from any computer on my network. So far so good. Just remember to use “sudo shutdown -h now” to shut down the pi before unplugging it!

Installing the camera The camera installation turned out to be the easiest part of the whole process. I just followed the instructions here. To take a picture, use the command “raspistill -o foo.jpg” (replacing “foo.jpg” with your desired file name). By default the camera waits 5 seconds before taking the picture. A little red light comes on on the camera to let you know it is taking the picture. Here is the first test photo I took of Alivia and me. We both look pretty tired:

Installing the printer Installing the printer also turned out not to be terribly difficult. Again, it was slightly complicated by needing to do everything remotely, but fortunately there were some easy workarounds. General instructions for installing CUPS (a Unix printing system) can be found here. I followed the instructions here to edit the configurations files for CUPS to allow remote setup. With the setup complete, I was able to print the test photo I took earlier. Here is the result:

On the left is the Rpi itself (it’s about the size of a credit card!). The printing was quite slow, but I think it will be faster if I use a lower resolution.

My work on the photo booth is just starting, but so far everything has gone relatively smoothly. In future posts, I will continue to describe my foray into DIY electronics. Next on my agenda is to install a wireless adapter and figure out how to use command line tools to edit the photos.

In the next post, I will go over how to use ImageMagick to edit and compile images into a single photostrip.

computing

## Site down

I received an email from a student informing me that my website was down last night. Apparently there was a problem with the database (MySQL was not running). After doing some troubleshooting, I attempted what should have been the first thing I tried: restarting the server. Seemed to do the trick.