This is a program I wrote to make my Pyboard act as an oscilloscope. It works by measuring the voltage using an analogue to digital converter and graphing the results. I wrote it while in vacation in Maine because I needed an oscilloscope to test if the 8-bit sound program I was making on my TI-84 was working or not.
It was initially just a Pyboard with an LCD and touch-sensor shield but then I added the reflective LCD, battery holder and 7 button "keyboard." I also made a few circuits to amplify audio output and protect the board in audio input.
On the back you can see the wiring on my attempt to use the 8 remaining touch sensors to make a slider at the top.
I like to write programs on my TI-84. I've used it so much that I took it apart and added a rechargeable Li-Ion battery to keep it from eating all my AAA batteries.
This program is a test of error propagation for dithering images. The test image is a 64x64 pixel 8 bit greyscale version of the common test image of Lena Sölderberg.
I also created a club at my school to teach people how to program their calculators.
On the presentation slide (link), I only put programs which I had made. I didn't want to say "this is what one can do." I wanted to say "This is what I've done and can teach you to do."
Silver Acetylide Double Salt
I synthesized minute quantities of SADS, a very brissive explosive, by bubbling acetylene gas through a solution of AgNO3 I made with a silver dollar and nitric acid. I detonated it by letting it dry and holding a flame under it. It's impressive how a dust sized piece of it can punch a hole through aluminum foil.
This was when a friend of mine came over to my house with aluminum powder and ammonium nitrate because he was also interested in pyrotechnics. I didn't have iron oxide to make traditional thermite, so I used copper oxide, reasoning that it would work and, in fact, be better. I was dangerously right. I didn't expect it to burn so quickly and shower molten copper everywhere. Luckily, by habit and rules, I had only made a few grams, so nothing went wrong.
Zinc Sulfur Rocket Fuel
This was a test of a rocket fuel involving zinc metal, sulfur, and maybe potassium nitrate (I'm not sure). I saw on YouTube that zinc sulfur rockets are a thing, so I decided to try to make some rocket fuel based on zinc. I never used it for my microrocketry because filing down pennies was a chore, but it could make a good green flash for the end or an interesting propellent for the beginning. ZnS rockets are weird. The product of the reaction is a solid, but they still generate enough gaseous products (sulfur vapor I think) to get decent thrust.
I found a type of skewer fits perfectly into a pipe adaptor when wrapped in tin foil. I used this to make precise diameter rockets. First I make an empty aluminum tube by wrapping the skewer in aluminum foil and putting it in the pipe fitting. Then I put flash powder in the aluminum foil tube and push it down with the skewer. Then I do the same for the rocket fuel. I finish by twisting the end, flattening it with the skewer, then drilling out a hole in the middle to a specific depth to control the thrust profile. I drill the hole with a tiny hand drill to avoid accidental ignition.
This is something I am really proud of. I didn't think I could make functioning fireworks less than a milliliter in volume. I thought I would at least need automation, but I found a technique of construction involving a pipe adaptor, a skewer, and aluminum foil that works. The fuel is homemade R-candy (KNO3 + sugar). The flash powder uses Strontium Nitrate and hand ground magnesium powder, again homemade. The fuse is charred string soaked in a saturated solution of NaNO3 and allowed to dry.
Laser Musical Stick
I had an idea about a laser harp that was more like a normal stringed instrument, in that each laser "string" could make multiple tones like a guitar string. My original idea for this was to use the time it took for the laser pulse to reflect to calculate the distance, but I ended up having to use the amplitude of the reflection instead. There is a tiny photovoltaic cell in the end of the pen cap that is reverse biased, so it acts as a receiver. The pen cap is to filter way extraneous light. The signal from the receiver is amplified and filtered for high frequency (τ is a few microseconds so LED lights don't mess it up) by a circuit designed by my dad and me. The result goes to the ADC pins of the Pyboard, which turns the laser on, measures, then turns it off and measures, taking the difference. It then uses that information to change the speed of the buffered waveform playback, thus changing the pitch. The output of the Pyboard is current amplified by two op-amps.
I programmed in many modes, keeping the old ones to compare to. I added quantization to make it sound nice. Since pure tones don't sound very natural, I computed the sample buffer with (bounded) random amplitudes for the first ten or so harmonics. I also have some modes experimenting with playing the buffer at different rates (thus different notes) through the left and right channels. I found that a ratio of 1 to 1.01 made a nice vibrato effect in the way that the three strings in a single piano note do.
Laser Harp by Paul Soulanille
Guitar by Paul Soulanille
I originally intended to make a stringed instrument which had a hinge. it would be played by bending the hinge to change the tension in the string. However I ended up making a normal (3 stringed) electric guitar. This was because I couldn't find any hinges strong enough to withstand the force, and I got distracted by the idea of making electric pickups. It uses hum-bucking pickups, which cancel out signals from far away, decreasing power line hum. I wound the pickups myself, around 200 turns each. I first used 42 AWG wire, then after removing my pickups to try to remake the electronics to be flush to the back, I used 36 AWG wire and the same number of turns. The preamp circuit is three op-amps on a virtual ground made by the fourth op-amp. They have potentiometers to control the gain.
Chaotic Circuit and other Electronic Experiments
My dad brought home an old analogue computer (it had vacuum tubes) and made this circuit he found online. It was quite slow though, and I wanted to hear the bifurcations in the path, so I made one using op-amps and signal capacitors so it was fast enough to hear. The video shows first a sweep through of the potentiometer that controls one of the factors. It then shows a few somewhat stable resonances I was lucky enough to get on video. The first two I got by poking the circuit with my finger, the last one appeared randomly and was fairly stable. The circuit models a differential equation that produces chaos kind of like the logistics map.
Circuit diagram of Chaotic Circuit
These are the secondary and primary coils of the Tesla coil I'm working on. The secondary uses 42 AWG wire around a glass tube. I modified a hand crank grinder to wind it quickly. I measured the inductance, but I don't remember the result right now.