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:

So, what’s happening here?

• A capacitor and a potentiometer (the one labelled ‘pitch’) work in tandem with two of the pins on the 40106 chip to create an oscillating signal. It’s a square wave - the simplest of electronic sounds (explain more!).
• This signal is sent to a potentiometer which controls the volume, and then out to a speaker (I used my earphones).
• The chip is also connected to power and ground, with a 9V battery used as power supply

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

• 10k, 100k and 1M potentiometers for the volume pot (the smaller the value, the better the range, more or less)
• 10 uF, 1,2uF and 0.1uF capacitors
• a 500k potentiometer, a light dependent resistor, and my skin as pitch controls. I also tried using the textile potentiometers I’ve developed in the past few weeks, but think I’ll need to adapt these a bit before they’ll work

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.

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:

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:

• Method 1: You put a 10k resistor between each oscillator’s output and your speaker. This way the oscillators don’t interact with each other. You can adjust and control each sound separately.
• Method 2: As shown in the diagram below, diodes are used to connect the outputs of the oscillators to the speakers. This results in the oscillators ‘modulating’ each other, which means they interact and make a whole range of mad sounds (in next week’s documentation I’ve filmed this actually happening).

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.

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#

• I created the design in Rhino3D, and imported it into Illustrator to do a bit of editing. Then I exported it as a .jpg (high quality!), size 14cm x 14cm, as that’s the maximum size the machine can embroider.
• On one computer in the lab we have a license for Embird, an embroidery program that can export to Janome’s .jef format. It looks like it was designed in the 1990s and never updated.
• On opening Embird, open the ‘Sfumato’ plugin. This allows you to convert images to stitch patterns.
• Open the image you want to embroider.
• Click and hold on the magic wand tool, and select whether you want to do straight stiches or fill in whole areas (e.g. ‘sfumato’ stitch) with stitching.
• Click on the parts of the image that you want to stitch - for the design we were doing, this was easy, as it was just one continuous black line. You can adjust the tolerance if it’s not catching enough of the pattern, or including too much.
• Click on ‘Generate Stitches’. You can repeat this process multiple times if your design has different colours.
• Export to .jef

Formatting the USB stick#

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

• Here’s a tutorial
• You also need to create a folder called ‘EMB’ on the USB stick.
• Save designs to EMBF folder that the machine will create within the EMB folder

Setting up the machine#

• Release the hoop and place fabric securely inside it. If using stretchy fabric, use appropriate backing.
• Click hoop back in the machine, lifting the presser foot to make space for the hoop to pass underneath the needle.
• Thread machine according to your particular machine’s instructions. In my final design, I used conductive thread as the bottom thread. But I wanted the conductive thread to be on top of the final design, so I just placed the fabric in the hoop upside down.
• Press the USB button and select your design. Your design will appear on the machine’s screen.
• Lower presser foot, and press start.
• Stop and start at any time by pressing the start button to pause.
• Reduce speed to minimum when working with conductive thread, to avoid tangles.

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.

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:

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:

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:

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 :)