This blog post is about the redesign of the capacitive sliders.
As I mentioned, the electrodes will wrap around the side of the acrylic pad. This allows for the soldering points to be hidden and not on the side which is touched. This was a problem in the previous prototype.
These tracks on the back will be covered by a strip of magnetic tape, which will fasten the pads to the legs.
Considering that I will be using a Roland GX-24 to cut A4 sheets of copper foil, I made this drawing to fit two pads per sheet:
It will leave lots of scrap material but I know from my experience with this machine that it needs quite a lot of material to grip onto (so although I might be able to physically fit another copy, it wouldn't work).
The reason for the zigzag pattern is micro-stepping, which allows for a better resolution. This is because pressing the area in between electrodes gives us an intermediate step. Therefore, although there are 6 electrodes on a pad, there's a total of 11 steps. For those of you who are considering designing touch sensors, I recommend these Application Notes.
Later on this week I will cut these, the acrylic pads and a couple of acrylic parts for the structure. Also, I have received the 3D printed parts so I will post an update about that soon.