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Input, Output and Channels of Communication

February 6, 2011

I’ve talked a lot about pneumatics.  Pneumatic and hydraulic systems are interesting to us because we have a better sense of how they work than electrical systems.  To understand electrical systems, we employ hydraulic analogies.  Our bodies employ pneumatic and hydraulic systems to carry nutrients and waste products.  If there’s a dearth of one, or an excess of the other, receptors send chemical electric signals more quickly than could the other two systems back to their prime movers to modify their behavior.  There are complex arrangements of valves throughout that together allow the system to behave as a great logic circuit.

I link here to my research on pneumatics for Rest of You:

Logic gates are still manufactured, so a circuit would not be difficult conceptually to construct:

Whole instruments have been built on this concept:

I’ve run into a few problems, however.  The first is that if the point is to make the logic visible, the logic gates should really be transparent in some way.  One wants to see this behavior:

AND Gate

OR Gate

NOT Gate


All circuit and gate diagrams are from  I’ll continue looking for these manufactured transparently, but I may need to make them.

The second problem is the scale of the circuit.  I’ve been talking about making a simple pneumatic computation machine–a calculator.  Assuming I could find a manufactured XOR gate (OR + NAND + AND), I would need 72 gates to build an 8-bit adding machine, if one follows the logic of Charles Petzold’s chapter on building “A Binary Adding Machine” in Code (p. 138).  That would be a machine that could add numbers from 0 to 255.  A lot of work for a fairly trivial accomplishment.  Possibly cool, but certainly trivial.

Greg Borenstein noted that he rarely uses his laptop to calculate, but rather primarily to send and receive media, and that I should focus on achieving something along those lines for output, as opposed to pure calculation.  Todd also suggested that I not put the technology first, but focus on the need, or aim, and let it dictate the technology.

Setting aside the pneumatic system as a calculation device for a bit, I’ll focus instead on its use as a communication channel in control and communication devices, looking at the input, output and application.

Musical Instruments as Input-Output Devices

I am fascinated by the bagpipe.  Reversing the hydraulic analogy for electricity, its bladder makes an optimal battery, and I’ve been thinking that it should be possible to generate a reasonable current off an outlet if the airflow is sufficiently concentrated and fast enough.  The air could be run over a light fan attached to a DC motor, and it would act like a small portable windmill.

These are remarkably compact input-output devices.  Pipe organs are also fascinating for many reasons, but for me especially when they cease to be free-standing instruments, or even fixtures of the usual and expected scale, but come to dominate and inform the character of the room they are in, of the architecture itself:

© Marie-Lan Nguyen / Wikimedia Commons,église_saint-Sauveur07.jpg

Possibly my favorite, though, is the pipe organ in The Carnival of Souls:

Stripped of any attempt to integrate it architecturally into its surroundings, it informs the character of those surroundings even more forcefully.  Uncased, its functional mechanism complements the unadorned early-20th century factory interior.

My other favorite is Tim Hawkinson’s Überorgan:

Photos by John Sullivan:

Pneumatic systems of course do not necessarily need to be used in the service of music.  They are designed as carriers of signals, packages, even humans, and can be urban in scale as well.  I’m thinking for instance of the pneumatic postal and subway tubes beneath the streets, and the steam tunnels.ásilky.jpg

Whether it actually uses city steam or not, Kristin Jones & Andrew Ginzel’s Metronome in Union Square appears to let that steam release its pressure as part of a larger time piece:

See here for criticism of this piece:

Chico MacMurtrie: Amorphic Robot Works

Finally, an example of a pneumatic power system used to control the motions of an enormous marionette and give it more human character than electric servos might.  Note the use of pneumatic logic gates for control function:

Transformation of the Communication Channel

If I were to set aside musical instruments and the control of marionettes, however, I’d have to admit that I’m having trouble still imagining an alternative output.  Greg’s suggestion that I think of the device more as a media controller struck a nerve.  In the part of my imagination where I just mash up different technologies and ideas to see where they lead, I had wondered what a bagpipe controller for an alternative to an LCD screen might be like — Daniel Rozin’s Wooden Mirror, for example (  The immediate question I have to ask myself is what would be the point?  Danny’s mirror is wonderful because it hides the camera and conveys a sense of magic and wonder.  I’m trying to reveal the parts, so how does magic and wonder fit in there?  Also, what is the point of the bagpipe in this scenario?  I do not seriously intend to do this, but I think it is important to try to answer these questions.  First off, magic and wonder should not be thrown out with the bathwater, but they should be shelved for the moment until I really do know what it is I fully intend to make.  Second off, I think the bagpipe gets involved here for a couple of reasons–and it doesn’t need to be a bagpipe or a mirror for that matter:

1. I’m looking for more fine-tuned control of the output, for the ability to input something, transform it, and output it.  The mirror is endlessly fascinating because it changes as you move about, but you cannot perform higher level transformations to the output.  I’ll need to develop this idea.

2. The transformation is key.  I’m looking to input something in one format, convert it, send it, receive it, and output it, possibly storing it for multiple output.

3. The beauty of the personal computer is that I click away on keys–plastic rectangles of some thickness with symbols on them–and any number of things suddenly appear on the screen in front of me, whether the pixel-representation of those symbols, or any other image or sound I design or call up.

This being said, and Greg’s and Todd’s suggestions taken to heart, I started thinking that maybe the pneumatic thing is being overplayed.  It might serve well for part of the mechanism, but the real point here is the transformation of a message through different media.  Greg had suggested I build an analog camera instead–not a camera that outputs to a film plate, but one that takes and stores its image in another way.  I would still need some logic circuits to control its function, but perhaps not as many as an 8-bit calculator.

I began thinking about how a digital camera’s charge coupling device works.  It is, at it’s simplest level, a two-dimensional array of photo-electric cells that produce 0’s and 1’s, and at a more sophisticated level, a similar array that produces a range of voltages that are then fed into an array of capacitors, storing them until they can get converted by an analog-to-digital converter into a number from 0-255.  I began thinking that trying to create a metaphor for the photoelectric effect might be just the launch point for converting the signal I was talking about.  I recalled as well my fascination last year with Alexander Graham Bell’s discovery of the photoacoustic effect and subsequent invention of the “Photophone”, the first wireless telephone.  Using a vocally modulated mirror, it translated sound vibrations into modulated lightwaves which could be captured with a selenium cell and converted back into sound.

Here’s a link to a great paper on the subject:

It may seem I’ve gone slightly off the rails here, but my thinking at this point is that if I could build two communication devices that convert sound to light and vice-versa, I will have achieved the transformation I’m talking about.  While I whole-heartedly endorse the reproduction of earlier inventions to learn how they work more fully, I don’t think I’m talking about reproducing the Photophone here.  Rather, I’m talking about something a bit more absurd, a phonic visualizer, a camera that takes pictures of your voice and stores them for playback.  The signal would be generated pneumatically, be converted into either light or sound, converted back into the other, and then outputted and/or stored, by which mechanical process to be determined depending on what tells the story most clearly.

It is time to do some sketching.



From → Thesis

One Comment
  1. Fascinating bit of lateral thinking here. Thank you for thinking “aloud” here.

    I found your page while looking into ideas for making a sculpture that used pneumatic logic elements to make its movements programmable. I’ve always liked pneumatics for the bio-friendly way it stores energy. This contrasts with the terribly unsatisfactory methods we currently have for storing electrical energy: batteries. They are mostly made of expensive and poisonous materials, are heavy, and must be discarded after use (even rechargeables don’t last very long considering the investment in them). I have a lot of computers, especially devices that require very low power to operate, but have become increasingly despairing of electrical storage. (I don’t think it will be solved until we have perfected super-capacitors modelled after spongey nature of our lungs or the fractal structure of the blood vessels in our bodies.)

    Recently I wrote (am still finishing, actually) a science fiction story ( which, in chapter 10, features some pneumatic machines. They use slightly offbeat mechanisms which I think could actually be built, which you may find interesting.

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