Soft Electrodes for Capacitive Sensing - Xiao Xiao
Motivation
So far in class, almost all of the sensors that we've played with have been resistivity-based. In a recent lab for another class, I built a simple circuit for capacity proximity sensing with a metal plate electrode. I was interested in seeing what would happen if I substituted the metal electrode with soft materials.
Experimentation
Before committing to create the fabric electrode, I tried out some materials to make sure it would work. I hooked up some conductive fabric to my original circuit (worked just fine). I also replaced the electrode with a spool of conductive thread. This worked enough to convince me that knitting a piece out of the thread might work.
Process
I wanted a thickly knit piece of material, so I started with trying to knit two 4-ply conductive yarns together in a stockinette stitch. For some reason, the knitting machine kept on jamming. I ended up making a piece of about 4'x4'. I had a bit of trouble binding off the material from the machine and ended up sewing up the cast-off end to prevent unraveling. I then steam-ironed the material to flatten it.
Miraculously, the original leftover circuit from sensors class worked pretty well with my knitted electrode. The LED starts turning on when my hand is about 1.5" from the electrode.
Lessons Learned
The knitting machine is finicky...
Pictures
