When coming up with this project I wanted to do something that would not only involve digital logic but also be interesting to others who may not otherwise be interested in the digital level. At the same time, because I was working without any partners, I wanted something that I knew I could accomplish, and that would still be impressive even if all the requirements were not fulfilled. I decided to make something that may not be the most useful thing in the world, but many would find fascinating. This is what I call a "Mid-Air" LED Sign.

The sign in the simplest of explanations is a set of LEDs that are programmed to display a text message. Many are familiar with LED signs that scroll like news tickers in stores and such, which are composed of a large array of LEDs. They are maybe seven LEDs tall and hundreds wide, so they can display a long message. But the way that my "Mid Air" sign differs is that mine is only one column of LEDs wide.

This is accomplished by moving the vertical column LEDs rapidly in a horizontal direction, and blinking them so they emulate each column of LEDs of a normal LED sign. This must happen very quickly, so fast that the eye does not pick up the horizontal movement. This in itself would make the message flash too quick for the eye to see. The display must repeat, with the message displayed in the exact same position several times so that the message seems like it is being continuously displayed. This functions much like the single beam of electrons in a television into tricking the eye that a whole image is being displayed at once. This process is what makes the message look like it is floating in mid air; the bright message is static to the viewer but the assembly is moving rapidly behind it and is blurred out.

I was inspired by this idea from a clock that I once had, that had a pendulum-like arm that contained the LEDs. It would be difficult, however, for me to construct a similar device, since it involves springs and other precision components. An alternative way is to spin it on a motor, which is easier to find parts for and build.

The mechanical side of things concerned me for a while, I was going to use a VCR motor and wood and pray glue would hold, but it dawned on me to dig up one of the best engineering tools that I was very familiar with several years ago: Legos! Not only did they enable me to construct a custom, sturdy assembly, they also had a motor and gears that were perfect for the application.

I decided to use blue LEDs mostly to enhance the visual effect. They are a new development in technology and are therefore expensive and rare. Their appearance is tantalizing on a dark background, and therefore would just make the project that much more impressive to a viewer. Note that any color LED can of course be used, however the resistor values will change.