Intro: Mini Oscillator Swatch
This swatch is a combination of interests put together for the eTextile SummerCamp 2015 Swatch Exchange. In the style of a kit, instructions are printed onto the fabric showing where all the pieces of the circuit go. I see this as a kit that someone would put together once they had purchased it including all parts. Seeing how this kit does not in fact exist (I would love to actually change some stuff and make into a real one some day), this 'ible tells you how to build this kit from scratch and then how to essentially put it together if you were to of purchased it. Perhaps you will find a useful technique here or do some bespoke kits of your own.
Techniques used are copper clad Kapton etching, printing onto fabric using an ink-jet printer, sewing and soldering.
The oscillation occurs when you hook up a resistor and capacitor to one of the inverter circuits in the IC. There are 6 inverters, so 6 potential oscillators. This circuit only uses one! The sewn yarn matrix acts as a variable resistor and 2 headers are used where the capacitor goes so you can swap out different ones to achieve different pitch ranges. Want to learn more about this circuit and how to build other simple musical circuits? Check out Nicolas Collin's Handmade Electronic Music.
Step 1: Gather Stuff
1 x 8.5" x 11" piece of white 100% cotton medium weight fabric (makes two swatch prints)
1 x 8.5" x 11" shipping label
1 x Small piece of copper clad Kapton
You can find pieces of this sold by DuPont under the name Pyralux
1 x CD40106 IC
1 x 9-volt battery snap
1 x 2-conductor male header snippit
1 x capacitor in the range of 1 - 10 microfarad
1 x surface mount 3.5 mm mono audio jack
1 x ~2" x 2.5" piece of neoprene or other thick material that will not fray when cut.
I used neoprene at 2mm thickness, I actually think thicker would be better.
1 x 3.5mm audio cable
1 x speaker that takes 3.5mm aux in or speaker/amp combo to get real noisy
1 x tapestry hand needle (large eye and sharp)
Soldering iron and supplies
Copper etching fluid
Sewing machine (I used one to sew the FCB to the swatch but this can be done by hand)
All files needed are attached!
Step 2: Print Fabric
There is another 'ible I wrote on this called How to Print Fabric at Home.
Basically you stiffen the piece of fabric by sticking the shipping label on the back then run it through the printer like a sheet of paper!
Step 3: Etch FCB
I tried a few different methods and stuck with etching using a vinyl resist cut on a Silhouette Cameo. My etchant? I used ferric chloride which is pretty nasty stuff and I would look into less harmful etchants if I were to do this again. It creates nasty gases when used and you need to properly dispose of it.
I encourage you to look into vinegar or other solutions like a mix of muriatic acid and peroxide if you don't already have a go-to.
I forget which 'ible I originally looked at to get the vinyl resist idea but this one seems great.
Step 4: Cut Key Template
There needs to be a spacer material between the rows and columns of the conductive yarn matrix. I used Neoprene for mine. However, if you have a laser cutter and trademarked Neoprene from DuPont, you should not laser cut it.
From the Dupont MSDS :
Conditions to avoid : Processing temperature > 200 °C (> 392 °F) Avoid heating for prolonged periods above the recommended upper processing limit.
Hazardous decomposition products: Hydrogen chloride, Carbon monoxide, Organic acids, Aldehydes, Alcohols
There are foams and rubbers you can laser cut but you need to check the MSDS first. If you are unsure about your foam and rubber use 100% sheep's wool felt instead. It will smell unpleasant (burning hair) when cut but will not damage* you or the machine.
*always make sure to work in a well ventilated area
Step 5: Solder Components to FCB and Sew to Fabric
Grab all the electrical components and solder them down to the FCB. It helps to drop solder down first on the spots on the board, tin the tip of the component you would like to solder and then touch the two points and apply heat to solder. The board pictured also has some solder on some traces which were fixes from a bad etch job.
If you want to use a sewing machine to attach the FCB to fabric, do that before you solder all the components. Otherwise, soldered electrical components will get in your way. If you hand sew the FCB, you can work around the components, although some will still be in your way and you won't be able to sew all the sway around the edge without producing gaps in stitching.
I dropped my solder, sewed the FCB then soldered all my components.
Step 6: Sew Conductive Yarn
Cut a length of yarn ~24" long, tie a knot at the end and thread it through the embroidery needle.
Start at the holes in the FCB and sew a couple times to secure some stitched. Stitch down to the red marks and use them as guides to sew rows back and forth as shown in the photos and printed illustrations.
As part of the printed instructions I have a step that tells you to sew the key template down, I actually didn't do this and want to swap out the template for something thicker so am glad I didn't. I encourage you to experiment with different thicknesses and not sew it down. Then, if you do find something you like for the key template, you can secure it any time.
Do the same for the columns (make sure they are two separate pieces of yarn) and you are finished!
Step 7: Play With Capacitors
You can swap out different values of capacitors to achieve a different pitch. Sometimes the chosen capacitor, with the resistor value, produces a sound too high or low to hear. With this yarn matrix you should be ok using a capacitor value printed in the instructions: 1 - 10 uF.
The timing resistor is fixed by design except for the variance you get by closing the intersecting yarns, but you can play with hooking up different variable resistors before sewing the matrix.
Step 8: Plug Into Amp/Speaker, Add Battery, and Play!
Grab a 3.5mm audio cable and plug it into a speaker or amp/speaker combo. Snap the 9 volt in and press a key. Sometimes the fuzziness of the yarn makes the "key" stick which is why I think a thicker key template is in order. Or perhaps a smoother conductive/resistive yarn.
That's what it takes! To create the "kit" and then to assemble it.
I do plan on redesigning this and making into a real kit, if you have any ideas that fall under commercial, contact me and maybe we can collaborate! I need a good swift kick to get it done, or at least get another iteration out...
Feel free to use any parts of this and to remix it for educational use!