Posted in Thesis
Tri-sensor Button
Aka shiny red, candy-like button…
History Eraser Button
emski* [AVS/MFL] | MySpace Video
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.
