7. Feb 18th-24th: More electronics prototyping & machine embroidery#

This week I’m building all my circuits in traditional prototype format - with hard components, on breadboards. The point of this is to reproduce classic sound-making circuits in their usual form, to make sure everything works before I start making soft versions.

It’s time to finally get around to making some sound ಠoಠ

The 40106 oscillator#

I started simple! After ordering a bunch of different CMOS ICs, resistors, potentiometers, and various other bits, I set about making a very simple oscillator. It’s basically this:

40106 oscillator

So, what’s happening here?

The values of the potentiometers and the capacitor change the sounds you can produce. Some variations I tried included:

I didn’t film any of this (I think because I was feeling self-conscious about making loud screeching/beeping noises in the lab - I got over this eventually). But basically, different combinations of capacitors and potentiometers allow different pitch ranges.

breadboarding collage

Next up: adding an amplifier#

The circuit I’m using in the previous sections uses and quick and dirty method to drop the volume of the signal to a level that makes it not-unbearably-loud and adjustable. Next I replaced the volume control potentiometer with a simple-but-powerful amplifier circuit, using the LM386 IC. That looks like this:

oscillator with amp

Multiple Oscillators - mixing#

The chip we’re using here - the 40106 Hex Schmitt Trigger - actually has six oscillators on it. Six! So it’s possible to set it up so that you have six little circuits like above, all producing different sounds (but we won’t be using all six).

There are two ways to do this:

oscillators mixed through dioes

Making soft resistors#

The next step was to start the transition from hard circuitry to soft, by making soft resistors.

Touch sensitive - using the body as resistor#

A really fun thing you can do with these circuits is use your body as a resistor, so that touching part of the circuit create sound (this is another thing that there’s a video of in next week’s documentation). My first soft resistors were loops of conductive thread sewn onto rubber fabric, as shown below. I also experimented with bending the legs of capacitors to make them more decorative.

conductive thread touch sensor

Embroidery experiments#

This week I also tried using the embroidery machine for the first time, with a lot of help from Cecilia!

How we set up the machine#

We have a Janome 200E Memory Craft embroidery machine in TextileLab Amsterdam. As embroidery machines, and their respective software, vary quite a bit, I’d recommend that you consult your machine’s user manual or online resources. But here are my basic instructions (mostly for future Jessica to remember how to do this). Check out this tutorial also.

Preparing the file#

Formatting the USB stick#

The machine will only recognise USB sticks that have been formatted.

Setting up the machine#

Turtlestitch is a great resource for coding designs to embroider on an embroidery machine, but unfortunately it’s not possible to export to .jef format, which is the only format the Janome machine will work with. But I highly recommend it if you have a machine that accepts the formats they do support!

Tests with regular thread#

The first thing we tried was a Hilbert curve design I made in Grasshopper in Week 5.

embroidery tests

It worked pretty well! Cecilia messed with the settings to force the machine to do the whole pattern in one continuous stitch (as it was insisting on doing one half, then doing a jump to the opposite corner, then doing the second half, for some reason). Because we did white on white, it’s not super easy to see the embroidered pattern, but it’s there ヽ(`ー` )ノ

Linen / steel thread#

The next thing to find out was whether the machine would consent to use conductive thread, or whether it would all jam up and be a big mess :)

First I tried a linen/steel thread (look up the brand name!). it’s quite stiff and tricky to work with, and when I tried using it as a top thread, it jammed up the machine and the thread broke. Like this:

failed conductive thread experiments

But when I switched to using it as a bottom thread, it worked really well. I apparently didn’t take pictures of this, but I refined this process for the final version I made, which is documented in week 11. The important thing to know is that it works well if the top and bottom thread have similar weights, and adjusting the tension is a good way to ensure that the stitches are smooth.

Touch screen thread#

I also wanted to try the ‘touch screen yarn’ we had in the lab, because it’s very very resistive, but I thought that if I embroidered it in a satin stitch, it could make a nice touch sensor. this yarn is very thin and also quite fluffy, so I expected some problems.

I wanted to try a different design, so I imported a new file into the embroidery machine software, one based on Daphne Oram’s work (go back to machine to figure out how you set the stitch type). This is how it looked with ordinary cotton thread:

oramics embroidery

I was actually able to make the touch screen yarn kind of work as the top thread, by trying different stitch types and adjusting the tension:

touch screen yarn

It helped to reduce the speed of the machine down to the minimum. And even with the tension adjusted, the bottom thread was still showing through to the top a bit. What might help with this would be to use a thread with a similar colour to the touch screen yarn, so that it’s not so noticeable.

I also managed to break a needle when the thread got jammed :)

broken needle