Summary

Demonstrating an unusual application of a CMOS NOR gate to implement a CMOS varactor controlled VCO, I explore the idea of circuit schematics as a music notation and how scholars and practitioners might create and analyze notations as part of the rich web of interactions that constitute current music practice.

Summary

I introduce a new synthesizable VCO using (n+1) mux2i cells from the SkyWater130 PDK to form a (2n+1) hybrid ring oscillator.

Intro

I am studying how IC routing is done in large chips. I am following advice I often give people that it is helpful to learn how to do something by hand before using an automation tool. I was skeptical about this for chip routing because the scale of the problem these routers solve (trillions of gates) is outside what can be done by hand. As it turns out a few of the things I know about routing PCBs helped prepare me for learning some of the conceptual and strategic aspects of what these tools do.

This alternative to the 555 timer for making audio oscillators is built from simpler building blocks (inverters) and has more versatility. You can find the schematics that correspond to the build video here: https://www.youtube.com/watch?v=CzO_ZKMSnAU

In a recent workshop on e-textile sound for the 2018 e-Textile Spring Camp, I provided a unifying framework for analog and digital sound synthesis and capacitive sensing techniques under the rubric of relaxation oscillators.

The following pages provide context for the workshop and include links to contributions from my co-teacher, Martin De Bie. This includes pointers to various iterations of his 555 timer-based Textilo project.

This project will be expanded ongoingly with further relaxation oscillator schemes.

History

There are few inaccurate histories of the 555 timer invention on the web so a good source is from the designer himself, e.g., http://semiconductormuseum.com/Transistors/LectureHall/Camenzind/Camenzi...

He also wrote several interesting books. The history and detailed design considerations are covered in a book he kindly made available as a PDF file before his death in 2012: http://www.designinganalogchips.com/_count/designinganalogchips.pdf

Circuits

This is a reasonable compendium of interesting circuits using the IC: http://www.555-timer-circuits.com

In the usual approach to PCB layout traces are laid out to connect signals and power to the pads of packaged parts and I/O connectors. This is a style that evolved for very high speed digital circuits. One usually also employs ground and/or power planes or a ground flood.

This style is not convenient for eTextile Appliqués which are most commonly single-sided and are based on cut traces rather than etched boards.

The entries in this table with an * were briefly reviewed in the 3 hour workshop the 2018 eTextile Spring camp. As the table shows, these are in the middle of the affordability/complexity/size axis and were selected for their potential in e-textile and wearable contexts. We had the good fortune to have Bela well represented in another workshop at the camp. Bela is transitioning to a new compact form factor which will make it easier to use with e-textiles.

I learned about this work as a teenager and managed to trace my fuzzy recollection while researching connections between textiles and electronics. It was published in Cybernetica Volume 2.

"I have recently completed building an electronic model of the 'growth net' principle and will now give a brief outline of its method of operation."

"What I described earlier as a common boundary now takes of the form of a moist fibre of cotton yarn connecting each input to the control grid of a pentode"

When I saw Martin De Bie's Textilo e-textile 555 oscillator I wondered if it could be extended to allow for body interactions with the pads using CMOS 555 timers in the spirit of the CrackleBox.

I tested this CMOS 555 breadboard version.

This informed suggested improvements to Textilo to Martin who came up with a textile layout which we used to teach during the audio workshop of e-textile Spring Break: https://www.youtube.com/watch?v=HdMsk6c3WGw

Alex blogged a great student perspective of this workshop.

I also brought along some PCB's which can be sewed to or pressed on Lego baseboards.