Description: In 6th grade at my elementary school there was a rite of passage called the electricity expo. You had to come up with an electrical circuit, build it, and fully document it. It was a major project and I wanted to make something really cool. All my friends were making something like the light + battery circuit that they teach you about as an introduction to electricity. The only thing that enabled you to tell their projects apart was the different games they adapted for electricity (think tinfoil balls, cups, and lights).
I did some research online and found out about these old wireless telegraph designs. I thought they were sufficiently cool and started creating my own. The first one I built used a circuit I found on the internet which used a detector diode and a cable connected to the plumbing in your house for ground. It worked poorly and I was not satisfied, so I decided to come up with my own design.
The thing that I created was based on a principle that I had learned about through trial and error a few years before, which is that if you take a radio apart and mess with the coil you can actually hear electrical circuits working. Motors sound like motors but amplified, remotes emit crazy beeps, and various other little clicks denote different events in any given circuit. The discovery was very useful to me and allowed me to gain a larger understanding of electronics.
I realized that I could use this principle of electrical interference to make a simple wireless telegraph. I took apart two of my junk radios and wired their parts together to get the best possible coil+amplifier combination possible. The reason I took multiple radios apart and combined them was that I had no idea how to tune them to hear the circuit; I had no standardized conversion method. Through trial and error I would eventually find a combo that worked.
Once the receiver was built I need to make a transmitter. Since my creation picked up interference, I needed something that put out a maximum amount of it. I knew that sparks=interference so the first thing I tried was short circuiting a 9 volt battery over and over with a wire. It made lots of clicks but was hard to hear. A little research showed that alarm bells make lots of sparks when they go off, so I bought one and turned it into a transmitter.
My mom helped me make a killer poster with various phrases for people to try out in Morse code, which I displayed along with my transmitter and receiver. A bunch of rice placed on the speaker (bouncing with the sound waves) completed the evil genius effect the complex circuit board had on my peers and teachers. I'm proud to say that this particular project netted me an A+.