More bird experiments

I continue to explore circuits for bird song creation. I'm working my way through various schematics found on the Internet, testing them to hear how different parts and configurations sound. So far, most of the bird circuits I've built fall into the "chirping canary" or "depressive parrot" categories. Just prior to this log, I discovered another schematic to try -- and it's accompanied by a really helpful video by Mario Burriel Valencia aka @DJ Mystic  https://youtu.be/W69VaPoPoVo

@DJ Mystic confirms what I have long suspected -- it's not only the shape of a waveform (sine, square, triangle, sawtooth, etc), or the component type (resistor, capacitor, transistor, etc), but the *specific make* of a component that can affect pitch, timbre, and loudness. This is especially true for transistors, and I have also seen variation in capacitors. ...Yes... I have read blogs by audiophiles discussing the pros and cons of specific parts for hi-fi equipment, but I didn't fully appreciate the importance of component specificity in low-cost sound generation. For some reason I assumed that since I work with cheap parts, the make wasn't that important. For example, I have thus-far thrown 2N3904 transistors at every problem they will solve. Now I realize the power of expanding my palette. Fortunately, I've got a friend coming down from the US and she's willing to bring a bag of electronics with her... so stay tuned for that excitement.

As for progress in the past few days, I bit the bullet and breadboarded a circuit with op amps. My attitude may seem weird considering that most synthesizer enthusiasts live and breathe op amps... but the dual power supply annoys me (and I've never gotten interesting effects with single supply op amps). Fortunately, some years ago, Bernie Hutchins gave me a useful schematic to convert voltage from a DC supply into a negative voltage of almost (not quite) the same magnitude. So if you have a 12 volt supply, you can produce negative 9-10 volts using a 555 timer and a handful of components. Please see my project files on Hackaday.io for this handy "Negative supply" circuit, or read about it on Electronotes.

The bird circuit that I built with op amps is described as "two canaries singing in a cage." You can find the schematic here: http://circuitos-de-electronica.blogspot.com/2007/10/canary-sound-simulator.html

I substituted a bunch of LM741s for the LM324​s because I don't like building in tight quarters. You can see the resulting circuit in this video​, where the "two canaries" are in the breadboard in the foreground (a previously built "transformer canary" is in the background):

I added some photocell resistors plus a few wires that you'll see me moving around (poor man's patch synth) to get variation in the circuit's behavior. It's pretty interesting, but maybe not worth the effort because there's a fair amount of complexity for sound effects that can be achieved with fewer parts. Still, I might make one of my electronic painting / sound studies with it because I like the aesthetic of crazy-complicated circuits.

Last but not least, here's a short video​ of a different bird circuit (the transformer one discussed in my previous log and shown in the background of the "two canary" video). I tested various capacitors and it's pretty cool the realistic bird sounds that you can achieve with such a simple component swap.

Still lots of work to be done.

New bird in town

​I've temporarily relocated the physical form of Hacking Nature's Musicians to the other-worldly environment of Tortuga Escondida (near Akumal, Mexico) for a one-month fellowship on los musicos de la selva​. Thankfully, my supplies made it through airport security and there's air conditioning to protect my electronic equipment against jungle humidity. Here's a photo of my bench showing a view of the jungle canopy and stairs to a roof deck with an amazing panorama over the electrically-charged ecosystem. (Giant scorpions occasionally grace my window screens but I have spared you that visual discomfort.)

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My electronics bench at Tortuga Escondida near Akumal, Mexico. October, 2018

A few observations before I jump into the main content of this log: (1) Tortuga Escondida seriously resembles a research facility from the TV series Lost​, so if I disappear you know what happened to me; and (2) the insects here are at least twice the size of their Virginian counterparts. Check out this insane Katydid!

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Amazing giant Katydid in the jungle around Tortuga Escondida (greater Akumal, Mexico). October, 2018

Amazing as the insects are, I'm not studying musical bugs because what's most remarkable to me --coming here from Virginia-- are the myriad species of birds. I've decided to see what I can do with the analog electrical engineering of bird song. 

As a starting point, I built a version of the classic, "chirping canary" used in kitschy artificial nature scenes. Check out my files on Hackaday.io for an annotated version of this schematic, which is based on audio transformer oscillation. Basically, the surge in DC power that happens when you first turn the circuit on is capacitively coupled across the transformer and continues to fluctuate thanks to a transistor switch. If you change (or remove) certain capacitor values, the circuit stops oscillating and makes an unpleasant tone that can be very loud due to the current gain across the transformer.

I've made a first informal video​ showing how the sound changes when different parts of the circuit are modified (apologies in advanced for some unpleasant beeps - don't wear headphones).

Next, I built a few astable multivibrators and connected them to various aspects of the sound-generating circuit in order to make the chirp sound more like a bird song. Some of my tests are documented in a second video that you can watch on Vimeo.

Watch the green LEDs (and follow the white wires) to get a sense for what the astable multivibrators are doing. 

Birds are very clever singer-songwriters, so it's going to take a lot more work on tempo and pitch variation to get interesting songs. I plan to try numerous strategies to generate voice quality because I want to build a jungle of different bird circuits ranging from sparrows to whippoorwills to parrots to owls to a Resplendent Quetzal, relative of the legendary Mayan Plumed Serpent. If you have suggestions for circuits to try, I would be grateful.

So... not only do my bird electronics need work, I could use a new "avian speaker" design. It seems that piezo buzzers are better suited to insects, while 8 ohm speakers have higher bird fidelity. Initially, this observation puzzled me (and I'm still not clear) but I got some useful clues from the ingenious musician, Nicolas Bras.​ It's material physics: the thin, metal vibrations of a piezo disk have more in common with the chitin instrumentation of an invertebrate than the fleshy air bladder and vocal chords of a squawking bird. Some insects do force air through a membrane, like living kazoos, but crickets rely heavily on the idiophonic effects of leg or wing rubbing. The sound made by an idiophone is quite different than that of an aerophone or membranophone, like hitting a cymbal versus blowing through a reed, the latter of which happens when a bird forces air through its vocal cords. I searched the web for homemade instruments that behave like an aerophone with a membrane and found this cool "membranophone" video​ by tachionics. 

As I did with my "insect-like" piezo, I'd like to build an electronically actuated speaker that has material properties more in common with a bird. I've got various 8 ohm speakers that are working for now, but I suspect that there's a better design to be made -- or at least some cool insights to discover in the process of trying. Again, your suggestions are greatly appreciated!

Stay tuned.

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This tarantula was found dead, but I couldn’t resist photographing its exquisite corpse. Impressive creature!

+ Electrolier Virginia + packing for Mexico

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It’s been a marathon recently… just finished “Electrolier (September night in Virginia),” submitted by files for the 2018 Hackaday Prize, and now I’m packing for Mexico. Stay tuned for updates from the jungle of Quintana Roo!

Electrolier (September night in Virginia)

​I've been working around the clock to finish my Hackaday Prize application and pack for Hacking Nature's Musicians in Mexico. As closure for my recent chapter, the various circuits that I've shown you over the past few weeks have migrated from my bench and into a sculpture titled "Electrolier (September night in Virginia)," 2018. Here​ is an informal video:

The video quality isn't great... (shot with my iPhone under bad lighting and extremely messy studio)... but hopefully you get the idea. The sculpture contains one instance of my Mother Nature board design, recognizable by the dense tangle of white wires connecting logic gates, and six sound generating "animal circuits" each with its own speaker. The colorful graphics are spray painted cardboard, and everything is hung on a tree structure under a moon (globe pendant bulb). Oh, and that large moth is made out of silk velvet that I dyed and embroidered with an old industrial "Ultramatic" machine​. I would have used small molex-style connectors to connect everything, but there was no time.

It's interesting that so many long wires didn't screw up my signals. I credit this to my use of common emitter amplifiers to buffer the signals, and the fact that I'm not drawing much current for anything you see (or hear). The whole sculpture is powered with a 12VDC / 1.5 amp power supply. I also used multiple 0.1 uF ceramic capacitors between power and ground on most of the individual perfboards. It's critical to remember power-ground capacitors when you're dealing with a lot of amplified signals banging on your power rails. I'm careful to avoid really small gauge wire, and I add many pathways to ground ("let ground abound.")

So... now I am packing my electronics bench into a suitcase and praying that security does not detain me at the airport. I'm throwing in packets of desiccant and crossing my fingers that jungle humidity doesn't zap everything. Making analog electronic circuits in the jungle will be interesting to say the least -- stay tuned for the sounds of los músicos de la naturaleza​ en Quintana Roo!

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Mother Nature in perfboard

I've been busy migrating my "Mother Nature" controller circuit out of my breadboard and into perfboard... and yes, it's insane but no, I don't have time to produce a printed circuit board because I'm leaving in six days for a fellowship in Mexico. For the record, I do not recommend soldering so many components and connections in perfboard because the risk of error is high, either from bad solder joints, signal interference, or just plain confusion. I plan to design a printed circuit board for future embodiments of Mother Nature. Stay tuned.

As you can see in my previous log, I'm surrounding my perfboard circuits with spray painted cardboard to make them look cool -- and by the way, you could use this quick-and-dirty strategy to make a "starving artist's badge" for the Hackday Superconference.

As for the design of my "Mother Nature Board," aka random pulse generator to trigger various events, I have some additional technical tips to share:

• Don't have logic ICs on hand? Build discrete transistor gates. This approach has the advantage of common components (NPN transistors, resistors, diodes) and you can add multiple inputs to the same gate -- which is useful if you discover that an event is triggering too often... just add another input to the gate and the outcome will become less frequent. Not triggering often enough? Remove or change an input to the gate. You can even tie an input to ground (or power) and let the other fluctuate. I use 2N3904 transistors for as many things as possible, but you could also build these cool light gates described by @Dr. Cockroach 

There's a limit to how many things you can drive directly with a signal such as the output of a logic gate. Good engineers read data sheets and calculate voltages and current at various locations in their circuit. Impatient engineers add a generic common emitter amplifier between the signal OUT from a logic device and the signal IN to whatever you're driving. This hand-waving approach to buffering will not work in all cases! But it will probably work for most slow logic applications where you want to transform a signal multiple times and drive some light loads. I'm an artist who prefers prototyping to math, so I work a lot with "try it and see" circuit design. Plus, I am not building a nuclear reactor. Note that a common emitter amplifier will invert your signal. Pay attention to whether you need your signal to be active high or active low. Note that a 555 timer in monostable aka one-shot configuration is looking for an active low input. If necessary, invert the signal again to get what you need.

Mosfets make great electrical "on/off" switches because they don't draw current on their gate (==the mosfet equivalent of a transistor's base). They just need a voltage. I use mosfets for the last step in my Mother Nature circuit, or the point at which I want to turn power on or off to a particular sound circuit (the load). Make sure you have a gate resistor to ground or voltage will "sit" on the gate even when the signal is low (and the mosfet won't turn off).

I hope these tips are helpful. To end this log, I give you a video showing my Mother Nature circuit in perfboard with two sound circuits hooked up. If you watch the LEDs carefully, you will see how certain combinations of logic are triggering the sound circuits. The cricket is wired up to chirp most of the time, whereas the Katydid is triggered less frequently. For this demo, I hooked up only two sound circuits because it's already hard to understand what is happening, and more circuits becomes a sort of natural chaos... which is my goal, as you will see in forthcoming logs.

Same signal, many sounds

I've been migrating my circuits out of the breadboard and into soldered form. I'm also hooking up speakers so that my sound generating circuits are ready for installation in a sculpture of Virginia's nocturnal ecosystem. Because most of my circuits use a custom piezo electric speaker (built with my own amplifier board), I have to install each piezo element into a physical housing... and there's some interesting "play" here. One electronic signal can generate many different sounds depending upon the speaker's physical design. Here's a video of me testing various installations of a piezo element for an insect that makes a steady background noise.

It's cool to experiment with the interface between electrical signal and material properties. It's also critical to get it right, or else the piezo element will make a horrible rattling or screeching. Even a tiny drop of glue (to fix the piezo element in place) will alter the sound quality --usually the pitch-- and superglue can sound different from rubber cement or hot glue or tape. All of this is no news to a human musician, who knows that a note ill-played (even slightly) is a fail, and teensy subtleties often make the difference between average sound quality and genius.

It is interesting to wonder what makes animals of the same species sound different in nature: is it their electrical impulse or their physical form? (Is it their schematic, their CAD file, or their bill of materials?) Members of the same species inherit the same circuit design as well as physique. External physical factors, such as climate, have some degree of influence over material properties of the body --for example, a dehydrated cricket sounds differently than the same cricket wet with rain; a fat frog sings a different tune than the same frog skinny; and so on and so forth. We also know that "animal circuits" are sensitive to electromagnetic fields, and capacitive coupling undoubtedly affects individuals in close proximity. I suspect that physical factors play a greater role in the variability of an individual's song if but for no other reason because birds sound the same whether they are sitting on a tree branch or an electrical transformer (at least, I think they do). PS: Eventually I will tackle the challenge of bird song, but their vocal complexity requires more computation... which is why I have started with insects.

To end this log, I leave you with one more video clip of my "background noise" insect. Here it is with a plastic spool installed over the piezo (now painted green, black, and white). The soldered perfboard is embedded in a cardboard cutout that is painted to look like a forest creature sounds. Soon, this mixed media object will be joined with other embellished animal circuits to build a vignette of nocturnal musicians.

lesser angle-winged katydid

Watercolor and analog electronic study of a Lesser Angle-winged Katydid, 2018. I plugged in a couple of crickets to give this fellow some natural context. To read more about how I made this, visit my project “Hacking Nature’s Musicians” : https://hackaday.io/project/161443-hacking-natures-musicians

Follow me on Hackaday

I have started a project to describe and share my analog electronic circuits designs so that people can better understand my electronic practice. My project, located on Hackaday.io, is called “Hacking Nature’s Musicians.” You can find it here: https://hackaday.io/project/161443-hacking-natures-musicians

In a recent project log, I describe how I create chirping crickets using discrete transistors. Check it out: https://hackaday.io/project/161443-hacking-natures-musicians/log/153312-crickets-natures-favorite-astable-multivibrator