analog electronics

New bird in town by kelly heaton

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.)

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!

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.

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

Mother Nature in perfboard by kelly heaton

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.

Kelly Heaton process electronic

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 

discrete_logic_gates.jpg

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.

common-emitter-amplifier.jpg

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).

mosfet-switch.jpg

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.

Kundalini, 2018 by kelly heaton

Kundalini, 2018 (detail). Watercolor, acrylic, and analog electronics on paper. 15" x 11" x 3"

Kundalini, 2018 (detail). Watercolor, acrylic, and analog electronics on paper. 15" x 11" x 3"

open studio: electronic sculpture garden by kelly heaton

A couple look at the green light emitted by an astable multivibrator living in the Electronic Sculpture Garden.  In the background, a child plays with a ceramic capacitor while two transistors look on.  Kelly Heaton, November 2015

Image description from left to right: (1) Entering the garden through one of four analog logic gates, in this case, the logical AND gate.  The colors of the resistors in the gate were chosen in honor of France.  (2) A scene with woman and child enjoying the garden.  The woman sits on a microprocessor, meanwhile her child plays tries to climb onto a vintage resistor.  A transistor and capacitor are in the background.  (3)  A woman regards a dead microprocessor.  In the background, a transistor is being overgrown by a twisting vine.  Other electronics have organic, natural forms that make them hard to distinguish from the surrounding vegetation.  (4) Detail of a vine overgrowing a transistor in a post-apocalyptic vision of the Electronic Sculpture Garden.

NOTES

I continue to create vignettes of my Electronic Sculpture Garden using miniatures and photography to convey a built environment.  Why am I doing this?  I want to bridge the consciousness gap between man and machine, to pull back the curtain of Oz, and especially to raise human understanding of the electronics that pervade modern industrialized cultures.  Most people are curious about how things work, but are uninterested in a steep learning curve.  Understanding electrical engineering is steep indeed. Electronic components are tiny and foreign, like characters in a strange alphabet.  Their energy-transforming behaviors are largely invisible, and circuit diagrams are gibberish to the untrained eye.  Even well-documented circuitry can be difficult to analyze and comprehend.  Thus, electrical engineering is pigeon-holed as geeky, meanwhile people of every generation, gender and nationality are becoming dependent on electricity (==God save us if the grid goes down for any length of time).  

Meanwhile we become dependent on manmade electronics, humanity is transforming the natural environment of earth.  Nature is truly the pinnacle of sophisticated electronic design: people, like all biological organisms, are energy consuming, transforming and expending machines.  One could argue that there’s no real distinction between nature and electronics because both are systems for energy transformation.  The real distinction concerns the maker: Man versus God or Nature (or whatever Entity you believe to be the creator of things not made by humans).

Why a garden?  People seem to have an easier time relating to things on our same physical scale.  Human-scale sculpture of electronic devices situated in a grassy landscape would be a playful and intriguing experience, like concrete dinosaurs in an amusement park.  Barriers to understanding (and prejudices against electronics) would -hopefully- be less than usual.  The green of a garden can be compared with the green of a classic circuit board, and everyone feels comfortable on a lawn.  Situating electronic sculpture within a formal garden is an opportunity to define the landscape in an entirely new way, yet draws upon a centuries-old tradition of gardens with fantastical sculpture.  In short, big electronic sculpture in a modern garden is cool.  

Another facet of garden design that interests me is the relationship between Man and Nature in the Anthropocene.  Here, I have more questions than answers...  Electronics transform energy, plants transform energy, but are they both alive?  As manmade objects increase in sophistication, will they eventually become as living as natural systems, even competing or merging with nature?  What happens when humans stop making electronic things (for example, due to an apocalypse); will "original" or "true" natural reclaim manmade artifacts, eventually composting most or all trace of human ingenuity?  I love the idea of vines twisting up the legs of a transistor, or flowers growing within a patch of resistors.  The visual effects are beautiful and intriguing, as are the conceptual implications.  

I will continue to explore these ideas in the design of my Electronic Sculpture Garden, and I will eventually publish a book with my findings.

electricity: breathing motor by kelly heaton

An astable multivibrator controls a Darlington amplifier to drive a small pager motor. The gently rising and falling motor speed simulates breathing or other natural undulations.  The addition of other control stages could add complexity, if that's what you want.

Circuit design by Kelly Heaton, 2014.  If you try to build this and it does not work, I'm sorry… I am more artist than engineer.  I sometimes struggle to reproduce my own circuit diagrams, but I have learned that tinkering with frustrating electronics is a great way to make new art.

This analog circuit is comprised of two parts: an astable multivibrator that creates a low-frequency square wave (left side) to switch on/off a Darlington amplifier (right side) that drives the pager motor.  I have added various capacitors and a resistor to the amplifier stage.  These affect the quality of the motor speed, making it turn on and off more naturally.  The video shows me removing / replacing the pull-up resistor on the emitter of the second NPN transistor, illustrating its function (to provide a baseline motor speed so that the motor does not come to a complete stop, but instead undulates between a faster and a slower speed).