1. Jan 7th-12th: Research & Textile potentiometers#
Over Christmas I was home in Dublin for nearly three weeks, and during that time I thought a lot about how I should go about my project. The goal is to make a modular e-textile synthesizer, but even though that sounds like a pretty clear plan, there are tons and tons of decisions to be made
What kind of synthesizer, exactly?#
This is the big question. In broad terms, a synthesizer is just something that turns electricity into sound. But beyond that, there are hundreds, if not thousands, of ways to go about that! During this week, and the weeks beforehand, I spent a lot of time researching different kinds of DIY synths. I was thinking about:
- The kind of sound I wanted my synth to be able to create
- The level of complexity in design that I’ll be able to achieve in three months
- Options for altering the sound / creating different modules
Recreating analog synths in fabric?#
The Little Bits synth kit is a great educational kit that allows you to snap together different modules to create a variety of synth sounds. I learned that the designs for all their modules are open source and online, so one option would be to take these designs and make textile versions.
Music from Outer Space - Sound Lab#
Music from Outer Space, aka MFOS, is a DIY synth website by Ray Wilson that is much loved within the synth community. The Sound Lab Mini Synth is a classic MFOS project that I also considered basing my project on:
However, once I actually looked at the circuit diagrams for both of these, I realised how much work it would be just to assemble all the parts and build this, let alone to design and test an e-textile version. This might not be the way to go (∪ ◡ ∪)
Starting somewhere: Atari Punk Console with textile potentiometers#
One kind of DIY synth I have made before is the Atari Punk Console. With just a few components, you can make a very raw-sounding little synth, with two potentiometers that control the sound:
I decided to build an Atari Punk Console on a breadboard and interact with it via textile potentiometers. I figured this would be a good starting point!
Every synthesizer needs some way for the user to interact with it to change the sound. And almost all of the time, the way this is done is: potentiometers!
A potentiometer is a strip of resistive material that has a ‘wiper’ that can be moved from one end of the resistive strip to the other, increasing or decreasing the resistance. Potentiometers can be used as variable voltage dividers or variable resistors, and normally they look something like this:
So to make an e-textile synthesizer, I need soft / textile potentiometers. Kobakant have a few examples of how to do this. I’m also sure I have one of these soft potentiometers from Plug and Wear somewhere, but I have yet to find it.
I wanted to get a simple synth on the go in the first week, and I had most of the parts I needed to make an Atari Punk Console, so I set about doing that. For this, I needed:
- 2 500k potentiometers
- 1 50k potentiometer
- a 556 timer IC, or 2 555 ICs
- Miscellaneous breadboard jumper cables
- A 9V battery
- A 9V battery clip
- A speaker
- 2 10 nF capacitors
- A 1k resistor
I’ve made Atari Punk Consoles before, but not enough that I’d remember how to put one together. I used this great Instructable by BrownDogGadgets as my guide. I did not remember to take pictures of the circuit assembled on the breadboard before I pulled it apart (ಠ‿ಠ)
The first textile potentiometer I made used a strip of silver-coated conductive fabric, a strip of velostat, and a piece of conductive thread to use as a ‘wiper’. This had a range of approximately 100 kΩ
The second textile potentiometer used a piece of stretchy resistive fabric, copper conductive thread, and a small piece of silver conductive fabric. This had a range of approximately 400 kΩ
And finally I tried using thread as the resistive element. I took some ‘touch screen yarn’ we had at TextileLab Amsterdam, which is very resistive. I wound it around two paperclips stuck to the table - doubling up the threads lowers the resistance, so I thought if I did this I could drop the resistance to a useful range. I didn’t quite get there - after wrapping the thread 20-30 times I had a 60 kΩ potentiometer (approximately), which is still a lot higher than the
Did it work?#
In a word, no. When I assembled my circuit, I had no sound. This could have been because:
- The potentiometers were in the wrong range
- The IC wasn’t working
- The capacitors weren’t the right value
- The battery I was using had run out
Without having a spare IC, a spare battery, and some regular (hard) potentiometers on hand to test this out, there wasn’t a whole lot I could do to figure out what was going wrong. So I decided to order some spare parts (which I still haven’t done) and try something else.
Another thing I spent a lot of time researching is how you can make a (decent sounding) synth that is built around an Arduino. You can do bery basic sound generation in Arduino very easily with the Tone library, but the range and complexity of the sound you can generate is limited.
Auduino is a project I came across that uses Arduino to make sound through ‘granular synthesis’ (no, I don’t know what it means either). This has quite an interesting range of sounds, and making a textile version of this could be fun:
Auduino with textile potentiometers#
I had a quick go at assembling an Auduino prototype (link to where you downloaded the code). I uploaded the code onto an Arduino Uno (Adafruit Flora unfortunately doesn’t have enough pins), made 5 textile potentiometers, and connected them to the Uno with alligator clips and breadboard jumpers.
I did get sound! And why didn’t I film this? :) Not quite the sound in the videos though. I need to figure out if that’s because my textile potentiometers weren’t working reliably, or if something else was going on.
One thing I really don’t get at the moment is that the Auduino documentation says that 5k-10k potentiometers should be used. But I don’t get why the value of the potentiometer is important, as it should be possible to map the minimum and maximum values of the potentiometer to any range within the Arduino code.
Again, I need to get some regular potentiometers and see if I can properly replicate the original project with these, then replace them one by one with textile pots.
Sequencers and keyboards#
I definitely want to have some kind of sequencer module - this is a module that takes the sound your synth is making, and changes the pitch to play several different notes in a sequence…
Why am I doing this again?#
Towards the end of this week I started to feel like I was getting stuck in the question of ‘What’s the best way to generate the kind of sounds I want to achieve?’, and losing sight of my other goals for the project. Ultimately, my Fabricademy project isn’t about faithfully replicating a classic synth in a soft format, and overcoming the issues with using conductive fabrics and threads instead of regular electronic components. This project is about seeing what new, interesting and unexpected things could come out of soft electronics, and about making a new kind of synthesizer that’s interesting to interact with, and illuminates some of the maths and physics that make the thing work (instead of hiding it in a literal black box).
So I decided that I needed to do a lot more research.