It’s best to get away from steel, I found aluminum and bronze wool that comes in affordable amounts here.
Here is an explanation given by lustersheen as to why bronze is better than steel wool:
“Unlike steel wool, which leaves behind small fibers that can rust and discolor wood in corrosive marine environments, Bronze wool resists shedding, rust, and corrosion.”
I covered the button, to make it the shiny red, candy-like button I always wanted which actually diminished the responsiveness a bit.
Adding more fluff in the top of the button to round it out
Red cover with binding around the bottom before cutting off excess
When I tried the button, I later found out that the extra fluff I put in the top made the button bounce back to the original shape nicely, but hindered the responsiveness. Sadly, I had to take it out in order to get the switch to close, it still takes some force and then does not bounce back. If the cover was a bit tighter, or I had added height below where I fixed the digital switch, the top would not appear concave after pressing it. A note for future generations.
In the videos you can also see the opening I left once I needed to get back in to remove the fluff that I had added to the top. Something I will fix later.
Regardless of it’s minor faults, I hooked it up to some out put. First I hooked it up to my Arduino and used the pitches.h library to create tones. I wasn’t able to get the two digital switches and the one analog to play together in the same program, so I included two different videos. The first is of the two separate digital switches playing two different notes.
Breadboard set up for the arduino with a piezo using the pitches.h library
This next one is the analog hooked up to play through several frequencies. It is hard to tell that there is any great range. Using this application did not seem the best way to get a nice sound, and I wasn’t too successful programming it correctly, so I didn’t play around with it too long. After this I decided to move my values over to Max/MSP.
I hooked up the red button to Max/MSP using existing patches I had. One digital is playing a note in a sequence every time it closes. The second one starts a new window with a constant bass noise, while playing a sound each time I close it. The analog is hooked to this same patch and changes the frequency of the bass. I believe I can get a better response with a clearer range just by changing the values of my range in my patch… but, this is a good start.
I’m able to go back and forth by hooking my bang up to start a new window each time I press each individual digital. Once the new window is started in one patch, the other one’s volume is shut off, allowing me to toggle between the two.
As the semester and my research progresses my goals are continuously changing. In order to keep my head clear and shine some light on my process, I will be actively posting them as they go through major shifts.
complete documentation thoroughly
- point to felt tutorial
- how to make a stable soft resistor
- how to make conductive felt
- how to tighten tension – top and bobbin tension
- voltage divider
- importance of pull-up and pull-down resistor
- put up tutorials on the elemental techniques of each sensor i.e. the yarn/elastic/cond. thread stretch sensor
Steel Wool Focus
using steel wool in sheeps wool to make uniform circuits
looking up fimo buttons, it’s called making a cane, and then cutting it.
roll up sensor
digital switches using steel wool
test resistance of steel wool
look up website for steel wool alternatives
show designs of sensor
- illustrate and post four main sensors with schematics onto blog
- make break down of major components i.e. how the stretch sensor was made in large green snake sensor.
- take nice pix
use of sensors
- put sensors into people’s hands and ask them to use them or give feedback
- get feedback on the documentation of the sensors if I can not get them into peoples hands
- post videos of data graphs and user interaction of four sensors
The idea is to build one button that you can push from the top and then squeeze on the two sides, one squeeze – digital switch, a squeeze perpendicular to that – analog switch. At first I imagined it with one digital switch on top, and two analogs on the side, but later decided that a digital could be more useful.
Initials sketches
Initial sketches
I decided to make on analog and two digitals instead.
Knowing how to make my analog switch form the previous successful sensor, the digital switch still needed figuring out.
If you take two pieces of conductive fabric and sandwich a piece of foam/neoprene/felt between them with a hole cut out. It keep the conductive pieces apart until you squeeze hard enough to connect through the hole, thus creating a push button.
Trying different thicknesses of felt for the digital switches
Testing thickness of felt for switch... this turned out too thick. The contact didn't happen consistently
From using my first dual pressure sensor, I realized I wasn’t happy with the pressure I needed to apply in order to get a reading. The sphere was too hard and not as squishy as I would like it.
To fix the problem, I grabbed some poly fill for stuffing dolls and pillows with in order to make myself a softer core to build the sensor around. As a covering, I find nylon pantyhose material to work best, really any thin fabric with great elasticity will work.
The foundation for my button
Showing the poly fill
Molding the fibers around the core
Continuing to needle felt the cover
FInished cover needing to be trimmed and attached to base
Now that I have a cover to my base, I can start building the mechanics of the sensors.
Stitched resistors
Placement of my resistor
Two stitched down pieces of conductive fabric that will make up one side of each of the two digital switches
Holding the other contact (blue) next to the one on the cover. This will be the side digital switch
Contact turned over to show the felt cushion that will be held between the two contacts
More or less, my components before I begin securing everything by hand sewing and needle felting
I also put tulle in between the conductive felt and resistor, otherwise it was a little too sensitive to pressure.
Notice the bit of tulle coming from beneath the pink conductive felt
Two blue digital switches (top and side), one analog (pink running along back)
WIth the switches secured, the leads and how to connect them to the microcontroller comes next. Using the existing threads from the stitched resistors, and creating new ones by sewing some to my fabric contacts, I sewed them all to one spot on the switch.
Stitched traces from all three switches
CONNECTION
How to connect these thread leads to my arduino? I tested a few different ways using crimp beads.
crimp bead on thread trace
The initial idea was to use the crimp bead as a platform to solder female headers to. The female headers ended up being too close together, once all the crimp beads were put on, the spacing would not align.
Female headers
Since the headers would not work, I decided the thread should be hooked straight to the wire of my ribbon cable.
Wire soldered to crimp bead
This proved to be really difficult, thread kept breaking or getting burnt off.
Broken thread
So, I went for a non-soldering method, crimping the wire and thread together in the bead and heat-shrinking around that.
I have found a way to control the resistance of using conductive felt. The trick is to build the conductive felt around a stable resistor. The was discovered by a suggestion from Eric Rosenthal and some tests I did by making a small ball of conductive felt and putting a 2.2K hard resistor in the middle. When I hooked up my multimeter to the two ends of the resistor using them as my leads, I was able to change the resistance by squeezing the conductive felt around it, the resistance went considerable down.
After I established this, I questioned whether or not I could make the stable resistor soft, while still keeping the range of values fixed. I remember seeing the suggestion of making a resistor out of stitching conductive thread on fabric using a sewing machine. I sat down at my machine and tried it out.
Stitched resistor using conductive thread, straight line on right for comparison
To my excitement, this worked really well. Only thing is, I would not be able to get a very large range unless I had the space to stitch on. The longer the stitch, the more resistive it would be. There is some resistive thread out there which I need to get my hands on, it boasts <1000K Ohms per 10 cm. This could work really well… all I need is the cash to get it…
With this discovery I decided it was time to construct a larger, more sophisticated sensor. My first was a sphere constructed with two analog sensors using two stitched resistors and conductive felt.
First, I needed to make a pattern for the shape in which to stitch the resistors in. The question was how to create a 3d sphere out of a 2d map. This lead me to Buckminster Fuller’s Dymaxion map.
How to fold a model of Spaceship Earth
This wasn’t quite right and would not work to create a smooth shape. It then occurred to me that I should look up the pattern for a tennis ball/baseball. (click on About Penn, then The Virtual Factory)
I made a pattern for my two resistors
Preparing to cut out my shapes with drawn on stitch lines
Following my stitch line
Each resistor had a different value from each other.
one was 420 Ohm
the other 360 Ohms
put in series 780 Ohms.
The piece of conductive felt gets wrapped around the two resistors, I pinned the corners to hold them while I needle felt them place.
The ends of my threads on each resistor (2 for each one, 4 in total) became my leads. When wrapping the conductive felt around them, I needed to make sure to pull these leads out before securing it.
Wrapped and pinned making sure to pull out all four of my thread leads
Needle felting the corners around the sphere
After I was done, I tested it, works well!
As of now, I am able to read one resistor, or both in series.
Within this post I am testing two types of conductive felted shapes. Some are made by needle felting using the conductive batts I made. Others are made by crocheting merino wool yarn/conductive thread mix, and then hand felting those pieces to shrink and tighten.
felted soft conductive materials
failed resistance test of conductive felt
This tendril was felted out of the first conductive batting I carded. It was thin and didn’t have enough steel wool distributed throughout, so I could not get a proper reading with the leads at either end while stretching and scrunching it up.
testing resistance
This is the 6.5″ medium length tendril from the first material test post. I felted it by machine and hand to the final length of 5″.
here is the resistance measured after I felted it up
- ~14 ohms relaxed
- ~6 ohms stretched
testing resistance of felted tendril
I crocheted another swatch specifically to felt. This is a 17×20 sc stitch swatch.
Before Felting
dimensions: 4.5″ x 4.25″
- ~3.5 Ohms relaxed
- ~1.7 Ohms stretched
read on the diagonal after felting
- ~ 5 ohms relaxed
- ~ 3 ohms stretched
NOTE: I believe that the felted and non felted readings should be considered synonymous. It seems that I might of just rounded up on the one for the felt, and since the readings always have a +/-2 ohm range in each state, they can be considered falling in the same range. aaaahhh… the inconsistencies of wearable tech….
small crocheted ball with pure wool yarn and conductive thread
I need to test other materials in order to see what other materials I can use to make a soft pressure sensor, moving onto felt medium, I needle felted a pure wool ball and wrapped it in conductive wool.
pure wool ball about to be wrapped by conductive batting
