Solder Practice

The first time I attempted to solder together a circuit was a complete disaster. All of the circuits I had created up to this point had been done on bread boards which do not require soldering. The reason for my failure was that I assumed circuit boards are set up in the same fashion as most breadboards. This is not true. It seems that circuit boards require close examination in order to determine how to set up your circuit. I had made the mistake of setting up my circuit on the circuit board in the exact same way I had set it up on the bread board. I had spent about six hours carefully soldering and de-soldering before I realized that my circuit was completely useless. On the bright side of things, the experience made me much better at soldering circuits. Re-doing the entire circuit correctly, took only about three hours. I also learned how to adapt my circuits to the interesting and sometimes confusing designs of circuit boards.

Bubbletron 4000

The Bubbletron 4000 is a giant, interactive, inflatable instrument/sculpture and was created by myself and Kirissa Grams. The first step to creating the Bubbletron was to tape many large sheets of clear plastic together into a large dome-like sphere. This sphere was about 8 ft wide on all sides and 12 ft tall when inflated. The “bubble” was inflated by connecting a large floor fan to the inside of the sphere with an 8 ft long tube made out of the same plastic material used for the “bubble”. We also created a hatch-like door on the side of the bubble so that we could get inside of the bubble once it was inflated. We then attached two different contact microphones to opposite walls inside of the bubble. These contact microphones were taken from the Kawasaki Drum Kit mentioned in an earlier blog. We soldered ¼ inch female jacks to the contact mics and then connected the microphones to multiple audio effect processors housed inside of the bubble. We also taped a contact microphone to the end of the inflation input tube. As air flowed into the bubble, the input tube flailed and waved around. The sound of the waving tube was also sent to an effects processor. All of the contact mics were amplified by a large amplifier and speakers housed inside of the bubble. The waving tube created a constantly changing sound that was very similar to the sound of thunder. The contact microphones placed on the inside walls of the bubble created very interesting sounds when the bubble was touched by someone on the outside. This sound changed depending on where the bubble was touched. The bubble could also be played by firing a “super soaker” at the sides of the bubble. All of the electronic equipment was protected from the water by the bubble walls. The bubble was set up outside on the St. Cloud State University campus and was up for about four hours. During this time, many different people interacted with the bubble and created many different unique sounds. One individual discovered that very dramatic squeaking sounds could be created by pushing their fingers hard across the plastic. The next time we set up the Bubbletron, it will have more contact mics and therefore, more potential sounds. We will also set it up earlier in the day when there is more foot traffic in the area.

4 for $4

The other day I visited a thrift store and picked up some old electronic toys. One of these toys was a Kawasaki Electronic Drum Set. The drum set is about the size of a shoe box, has 4 different drum pads and only cost $4. I dismantled the drum set and found that there was a contact microphone glued to the backside of each of the drum pads. When the drum pads were impacted, the contact mics created a signal which triggered a sample of a drum sound. The signal sent by the contact microphones is actually the sound of the impact on the drum pad, however, this signal was used by the toy to trigger a pre made drum sound. The chip inside of the toy also stored samples of music which could be triggered by buttons on the surface of the toy. The tempo and volume of the music could be controlled by two fader switches. While tinkering with the toy, I found that I could also control the tempo of the music by licking my finger and pressing it to different areas of the chip. The tempo change was much more radical and unpredictable with this method. This method also caused the audio to suddenly cut out. Flipping the power switch off and then back on again fixed this problem, but had to be done every time the audio cut out. I decided to disconnect the contact microphones and drum pads in order to use them for a future project.

Deep Contact

Air microphones are not the only way to amplify real world sounds. In DIY Audio, we also made contact microphones. Contact microphones are placed in direct contact with an object then amplify the vibrations of that object. We made our contact microphones by opening a piezo buzzer and removing the copper and quartz plate inside. We then soldered the two wires coming from the copper plate to an 1/8th inch male connector. The copper plate is glued to a very thin piece of quartz. When quartz is compressed, it creates a very small electronic signal. When the copper plate is pressed against a surface, vibrations from that surface compress the quartz and create a signal representative of the surface vibrations. This signal can then be amplified. When we plugged the copper/quartz plate (contact mic) into our mini amplifiers we were able to create all kinds of interesting sounds. Contact mics can be used to amplify heart beats. They can also be used to turn ordinary objects into musical instruments. Contact mics are best used for percussive sounds. These microphones can also be used underwater which is one of their biggest advantages over air microphones.

Air Microphones

In DIY audio we made air microphones by soldering a 9 volt battery connector to a resistor, capacitor, and two female 1/8th inch connectors. We connected the microphone piece to one of the female connectors and then connected our miniature amplifiers to the other. The air microphone creates an electrical signal when the small diaphragm in the microphone piece is moved back and forth. These movements are created by the vibrations in the air otherwise known as sound. Air vibrations are known as compressions and rarefactions. The nine volt battery, resistor, and capacitor amplified the signal sent by the air microphone. This microphone was surprisingly effective and inexpensive. These microphones are easy to make and are also very compact. It would be easy to hide these microphones in a space for an installation or performance.

The Final Failure

Advice to future DIYers: Don't drink a pot of coffee before you begin soldering your final project together. I usually pride myself on my soldering skills, but I'm usually not shaking due to copious caffeine consumption. Truthfully, I never figured out what went wrong with my final project. It was basically the circuit I outlined below (see "Recipe for my favorite oscillator") but I think something went wrong with the amplification area of the circuit. I thought it might be some problem with solder dots touching, but as I tried to clean it up, I made the connections progressively worse and eventually connected 5 pins of my 14093 to each other with a big blob of solder. After scraping the connections clear with a knife my circuit buzzes quietly; a pale shadow of its former self. I'll try to salvage it sometime, I don't like the idea of wasting such a wonderful chip.

Anyway, it's been an enlightening journey in DIY class. I learned a lot about electricity and sound. I got to listen to my hair. I will forever treasure my radio-shack mini-amp and the assortment of tiny electrical components which currently litter my carpet. I still think the class needs more enameled copper coils though. Many thanks to Dr. Twombly and my classmates. Have a safe and productive summer everyone!

Amp Chip 386N

Tiny and useful. Cut out the middleman! This circuit should be pushed back earlier in the semester. Once we built it I was able to apply my chips to the happy task of oscillating all the random speakers that are scattered around my room. No more restrictive mini-amp. Better yet, you can build the 200-gain variation and listen to the distortion as your speaker attempts to cope with the ridiculous amount of power. And it uses one less battery than the typical mini-amp setup. This was a vital piece of my final project (and sadly the source of its failure) but after I dig it out of the circuit board I'm sure I'll be using it again.

I assume if you made a fancy little case for a circuit like this you could undercut radio-shack by selling the things for 10 bucks on ebay.

That Amplitude Follower / Gate Thingy

By far the most complicated circuit we built in class. I understand the uses it might have but in my opinion the returns don't warrant the effort. Other than making mp3 players sputter with oscillator controlled volume it doesn't seem to serve much purpose. I mean, the lights are pretty and all, but I want my circuits to generate sounds not follow them. I suppose if you were building a stereo it would be a useful indicator of volume, but I don't frequently build stereos. And what happened to our class playtime? That's the best part! Another note to Twombly: Don't cut out playtime. Also, get some of those frequency divider chips next time around, simpler and way cooler than amp tracking.


Hmmm... now that I think about it though, it might be interesting to modulate the amplitude of one oscillator with another oscillator. Perhaps a summer project?

Guitar Pickups

Our Guitar Pickups combine two of my favorite things: Powerful magnets, and copper coils. I don't quite understand how a magnet that is glued into the center of the spool can vibrate enough to induce a current. But it does, and I guess that's all I really need to know. My guitar was a soprano as I could only find a two foot stick. Fun but tragically limited to the fundamental and harmonics by the single string setup. Frets would be useful. I thought it might be fun to pair a series of pickups to a few strings, but I found out someone beat me to it already. I briefly experimented with trying to pickup signals from other things, but results were similar to a poorly constructed telephone pickup.

I'm much more interested in building the inverse of a pickup: a speaker. Note to Twombly: consider adding a speaker assembly day, there was a disappointing lack of copper coils this semester. Better yet, build the amp circuit and a speaker early on and we can use homemade speakers on the other projects.

The Fourteen-o-Nine-Three!

Finally! Clean, pure, digital, clarity. My radio-shack mini amp hums and bleeps with modulated magnificence.

Recipe for my favorite oscillator:

Input 1: +, Input 2: cap 47uf to -, Output 1: Route to Input 3, Input 4: cap 4.7uf to -, Output 2: Route to Input 5, Input 6: 2.2uf to -, Gound pin 7 and hook pin 14 to positive. Put some pots between even numbered inputs and their relative outputs and listen to the difference between Output 3 and ground.

Best chip ever. It provides countless hours of entertainment and a clean form of modulation between oscillators. Hook it up to a guitar amplifier and play around with reverb and wah-wah effects. Hook it up to the amplitude gate and make your favorite tunes throb with intensity. Hook it up to a subwoofer and shake the dust off your furniture. Add some LEDs and you've got a festive Christmas decoration. Connect it to the pickup coil and broadcast your signal into the aether. Matrix two of them and you have eight oscillators at your fingertips. Run jumper cables between random points and observe results. Limitless potential!

The Hex Schmitt Trigger aka 74C14

Bad integrated circuit! Very bad! Your oscillators fail to maintain independence from one another! Bad! I've never liked this chip. Six oscillators sounds like a great deal, until you realize that they all leak into each other and form an ugly jumble of sounds. I attempted to use a series of diodes and resistors detailed in the textbook to separate them; still an ugly jumble. Some people might enjoy ugly jumbles, I do not. Synthesized sounds should be clean and pure, or dirty with intermittent bits of purity, or clean with bits of impurity, but never ugly jumbles. The only way to isolate the signals is to use an amplifier for each one. Who can afford that many batteries? You can get one good oscillator out of this thing. Don't try any more because it will sound like an ugly jumble. I suppose this is the downside to using circuitry that was never intended for sound applications. I guess it's possible I wired it incorrectly, or I have a bad chip; but the 14093 is so much more awesome that I don't even want to look at a Hex Schmitt again.

Childhood Distortions

Who doesn't love to hack the toys? I fondly recall the drunken ramblings of my Leapfrog Phonics Teacher as she lethargically inquired if I could spell "cat" whilst the inner workings of her brain were being subjected to ungodly abuses at my hands. Curse her surface mounted resistors! I was never able to wire in a potentiometer, so satisfied myself by removing components until her voice became indistinguishable. Can you spell: spare parts?

I had better luck with the nameless pan-cultural child depicted on the front of my Playschool cellular phone. At least he was kind enough to show an interest in whatever I was doing that day. His circuits were large enough to allow variable resistor control. Useful for speeding up dull conversations.

Experiments with voltage starving (suggested by the textbook) were ineffective for both of these toys. I think it'd be more interesting to tamper with a less "scripted" toy such as a keyboard. If you watched the DVD that came with our book then you saw the Casio circuit beneath the ornamental waterfall. Awesome.

The Electret Microphone

My knowledge of Electret Microphones is limited, even after an extended visit to Wikipedia I still don't know much about them. Apparently, electret microphones have a permanent static charge stored inside a dielectric material, this removes the need for phantom power to the capacitor which is required in traditional condenser microphones. You still need a powered preamplifier though. They make them by melting plastic in an electric field or something. It seems the main advantage of the electret mic is its cheap production cost. Wiki says your cellphones and computers probably use them, and over 1 billion are produced every year.

I'll be honest, I'm not a big fan of microphones. In my opinion sound synthesis is so much cooler than sound reproduction. Granted you can probably find some way to take the output of the microphone and alter it (say filtration via aforementioned contact mic), but I'd rather spend my time with the mathematical purity of integrated circuit oscillators. Mmmmm....integrated circuit oscillators. I also find it rather annoying that getting this thing to make audible sound requires an additional 9 volt battery. I don't have the money to support such lavish power needs. I'd rather save my cash and listen to my hair with the contact mic.

Contact Mics!

Piezoelectricity! What a word. It's the primary component of the so called "contact microphone." Tiny fluctuations within the piezoelectric disk transform manual force into voltage. I love these things. They're like magnifying glasses for your ears. How often have you wanted to listen to the sound of your individual strands of hair, only to be hampered by your pitiful human ears? Now you can! Compare the sounds of fabrics like wool, cotton, and polyester. Hear the dull thud of rocks falling on two by fours. Or revel in the glory of the plucked spring! Beware or pursue the feedback loops created when speaker and mic are in contact with the same object.

Interesting filter effects can be obtained using two contact microphones transmitting vibrations across a material; spring, metal, plastic, wood, anything rigid will do. Attach them to conventional instruments like tubas or flutes and observe results. It's too bad the tiny wires attached to my disk broke off, or I would be listening intently to sounds of my keyboard right now.

DIY: Early Endeavors

OK, I realize writing all ten posts on the last day possible is probably not the best approach to this assignment. That said, let's just pretend I haven't been procrastinating all semester and think back to those first magical days of DIY.

The Speaker and the 9 volt battery:

Oh how I love the simple principles of electromagnetism which control our modern speakers. Succinctly put: a tiny copper coil, wrapped around a paper cylinder, and suspended in a permanent magnetic field. Electrify the coil, and the wonders of nature shall bestow magnetism upon the coil, causing it to be repelled or attracted to field the permanent magnet. We exploited this property early in class by interfering with the circuit; include a semi-conductive material (such as rusted metal or graphite) and drag the contact across it. Your ears will be treated to a satisfying series of pops and snaps as the current struggles to complete itself. Paperclips connected to opposite ends of the circuit and placed within the speaker cone create an unusual feedback device; as the speaker cone vibrates, it alternates between completing and breaking the circuit. If adjusted appropriately, this kind of circuit can almost produce a sound vaguely reminiscent of an actual frequency. Astounding! Other ideas? Toss in some random pieces of metal; screws, nails, coins, broken glass, etc. Cut/rip/punch large holes in the speaker cone and observe results. Or submerge your speaker in water and see how long it lasts (after about 10 minutes my cone became quite soggy and would generate delicious sputtering sounds as it died). After you are finished abusing your speaker, hook it up to a stereo system and check to see if popular music sounds any better. If so, immediately patent your design.