Shift registers /  by kelly heaton

I am in the process of building a control system for the insects in my latest Electrolier. As a starting point, I will use shift registers with (or possibly without) linear feedback. Adding linear feedback involves "tapping" two or more of the logical outputs, evaluating their state with boolean logic (usually an XOR gate), and feeding the result back into the start of the shifting sequence. In my video, you can see two 8-bit shift registers in the center (TI part number CD54/74AC164E). I put LEDs on the logic outputs Q0-Q7 to visualize what is happening. As you can see, the LEDs of the two shift registers are not synchronized, a property of an undefined starting state that I will exploit to get randomness for "free" -- at least that's what I'm thinking.

More about my breadboard: on the right is a 555 timer in astable mode which provides a clock pulse of about 1x per second. On the left is a 5 volt regulator - this part is irrelevant if you have the correct DC supply voltage, but mine is 12 VDC.

Good general overview to answer the question “what is a linear feedback shift register” (LFSR):
https://zipcpu.com/dsp/2017/11/11/lfsr-example.html

On choosing taps for a linear feedback shift register:
https://cs.stackexchange.com/questions/1121/choosing-taps-for-linear-feedback-shift-register

Mini project on how to implement a LFSR: https://www.slideshare.net/KishoreChandrahasVanam/lfsr

Another helpful paper on using an 8-bit LFSR (i.e. Texas Instruments chip CD54/74AC164):
https://pdfs.semanticscholar.org/320a/8b2e781ac6165b400eca96047489685fd1f7.pdf

One final note: because shift registers are comprised of flip flops, an option to add true randomness to this otherwise pseudorandom bit generator is to exploit the metastability characteristics of a flip-flop as described here by @crj11: https://electronics.stackexchange.com/questions/394557/old-school-pseudorandom-pulse-generator-requesting-assistance-with-hardware-des?noredirect=1#comment965703_394557

Papercraft tree WIP /  by kelly heaton

I continue to work on my latest Electrolier sculpture. For this part --an arboreal vignette (and habitat for electric creatures of the Virginian night)-- I designed a sculptural tree in Blender that I unwrapped, print, cut, and folded to make branches out of relatively thin paper. I used this first collection of paper branches to build an underlying structure for my sculpture, like a naked tree. I stabilized it with wood glue and expandable foam. At the moment I am applying a bark layer which I laser cut out of cardboard using the same sequence of branch patterns. Because I am layering identical patterns, and because the real world is imperfect, the bark does not wrap around the circumference of the underlying tree exactly. I fill occasional gaps in the bark by hand, which gives an organic feeling to the machine aesthetic.

Whoever believes that technology makes production easier or faster has not witnessed my painstaking practice to balance artist and computer, nature and machine. For more information on process, please refer to my earlier blog entry: https://www.kellyheatonstudio.com/blog/2018/8/1/modeling-tree-branches

Below are several images of my process thus far. Note that this is the first of two interlocking branches.

Landscape studies /  by kelly heaton

Studying the landscape, sound structures, and insects real and imagined.

August insects /  by kelly heaton

Landscape painting and analog electronic soundscape (detail of work in-progress). August 2018

Landscape painting and analog electronic soundscape (detail of work in-progress). August 2018

I create the sound of a buzzy August insect using a 555 timer to drive a transistor astable multivibrator (to give timbre). Another slow astable multivibrator provides pulse input to a 555 timer in monostable configuration, that gives a pulse out to the base resistor of an astable multivibrator that sets the tempo. That's why the insect rattles for awhile and then stops (monostable 555 goes high - the rattle tempo is active low).

Prototyping Night Insects /  by kelly heaton

Here I am at my bench prototyping various analog electronic insects for my latest "electrolier" sculpture. The sounds are made using a combination of astable multivibrators (oscillators), some of which create the audio timber and others establish a chirp-like tempo. The speakers are custom piezo electric devices that I have physically modified to achieve different sound qualities, such as brighter versus muffled and close versus distant. Individuality is achieved by subtle variations in the electrical signal and the output device.

Modeling tree branches /  by kelly heaton

Using Blender to model and Pepakura to produce paper patterns for tree branches.