Square Root of Not

My wife bought me a “selfie-stick” (sometimes called Wand of Narcissus), which is ironic since I so rarely actually take selfies. But, once I took a look at its simplicity of design, I couldn’t leave well enough alone and decided to create the “Super Selfie-Stick.” At first I tried attaching a camera mount on the end of a golf ball retriever.

I finally received a Foldscope beta test kit. “Foldscope is an origami-based print-and-fold optical microscope that can be assembled from a flat sheet of paper,” according to the website. The Foldscope “can provide over 2,000X magnification with sub-micron resolution (800nm), weighs less than two nickels (8.8 g), is small enough to fit in a pocket (70 × 20 × 2 mm3), requires no external power, and can survive being dropped from a 3-story building or stepped on by a person.”

The kit came with instructions, perforated cardboard for the microscope assembly parts, lenses, magnetic strips to attach the microscope to a cell phone, and a light module.

The diode has a number of applications in electronic circuits. One application you may be familiar with is a rectifier. A rectifier converts alternating current (AC) to direct current (DC). Alternating current periodically changes direction while direct current only flows in one direction. "The most common function of a diode," according to Wikipedia, "is to allow an electric current to pass in one direction (called the diode's forward direction), while blocking current in the opposite direction (the reverse direction)." It’s easy to demonstrate how the diode will let current flow in one direction but block the flow of current in the opposite direction.

Parts needed:

What’s a relay? You’ve probably seen a relay race where one runner hands off a baton to another runner. Similarly, an electronic relay hands off control from one circuit to another. A relay is a very simple device consisting of an electromagnet, an armature (a switch that closes when attracted by the electromagnet), and a spring that is connected to the armature.

(Diagram inspired by: http://electronics.howstuffworks.com/relay1.htm)

In my previous article about the Kano Computer, I demonstrated how to use MIT’s Scratch graphical programming language on the Kano to flash an LED (the “Hello World!” program of hardware hacking). In this article, I’ll again demonstrate how to flash an LED, but using a special variable in Scratch called “MotorA”. Scratch automatically handles all of the programming for MotorA to produce a “pulse width modulation” (PWM) signal on Pin 11 of the Raspberry Pi. For a primer on pulse width modulation, see this article.

I've lost count of how many computers I've built over the years, but I think it is safe to say that the Kano Computer was the easiest build ever. So simple a child could do it. Kano founders, Yonatan Raz-Fridman, Alex Klein, and Saul Klein, wanted to figure out what the next generation’s computer would be like, so they asked Micah, Saul’s seven-year-old son.

You can build a simple circuit using two 555 Timer ICs to create an H-bridge that will drive a single motor in forward or reverse. An H-bridge circuit is often used in robotics to reverse the polarity of a motor. For example, if the motor is spinning in the forward direction, the robot will move forward and when the polarity of the motor is reversed, the motor will spin in the opposite direction and the robot will move backward.

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The diagram of the circuit resembles the letter “H” where the motor is the cross-bar and four switches form the legs.

A tone generator is a useful piece of test equipment used, for example, to test the frequency range of audio equipment such as your stereo or the external speakers for your iPod. A tone generator can also be used to tune a musical instrument such as a guitar. You can make a simple tone generator using a 555 Timer IC, a capacitor, potentiometer, speaker, and a power source (circuit pictured above). Here’s the schematic:

The NSA is not allowed to gather intel on US citizens (at least not without a FISA court order), but there is an obscure Reagan era loophole--Executive Order 12333, or Twelve Triple Three--that allows NSA to scoop up data on millions of Americans and store these data (about 350 billion searchable records—that’s “billion” with a “B”) for up to five years.

You can easily build a Cartesian diver toy using an empty one liter soda bottle (with the label torn off), a ketchup packet, and tap water. You may want to have a few ketchup packets on hand and put them in a cup of water to see if they sink or float. Keep the one that floats and use the rest for your French fries.

In a previous article I demonstrated how to use a One Time Pad cipher using a pen, paper, and Scrabble tiles (or Boggle cubes). If used correctly, One Time Pads cannot be broken by the NSA or any intelligence service on Earth because the One Time Pad keys use a randomly generated set of letters or numbers to encrypt your message.

Birdsnap is an iPhone and web based app that uses many of the techniques of facial recognition software to identify 500 of the most common North American birds. The web based version of Birdsnap is actually very easy to use: upload your picture, click on the bird’s eye, click on the bird’s tail, enter your location along with the date the picture was taken, and click submit. I’ll demonstrate how to use Birdsnap even though it was unable to identify the bird I submitted.

Last Wednesday I played golf at South Grove Golf course and my cousin snapped the following picture near the 9th hole tee: