Keyboard Matrix

A few weeks ago I found the keyboard and mouse button component of a dell laptop in the trash. The things people throw out these days! I immediately brought it home and started taking it apart. When I peeled off each plastic button, and removed the housing they rest in, I found a plastic sheet folded onto itself with many busses and nodes. When a key is pressed, the two sides of the circuit join at two nodes and connect one bus to another. These intersections are sort of like a Cartesian space but with really convoluted rows and columns that twist around and do all kinds of nasty things. Appearances aside, we are talking about a two-dimensional matrix. Perfect for mixing a bunch of inputs to a bunch of outputs, for example, or for, say, typing on a keyboard.

In this floppy, thin, somewhat translucent form, the mixing matrix is ideal for sewing into clothing or mounting onto a sculpture. In addition, it's ideal for making feedback loops between many components, kind of like how I was using a commercial mixer with the Braxton ensemble so many years ago. The possibilities all seem to point toward an expressive, unusual instrument of some kind.

The only issue is, since the rows and columns are actually this really twisted knot, how do I know what will connect to what?? Well, the only way to figure it out is the old trial-and-error approach. Or I guess I could look it up... Nah this is more fun! My secret agenda for that standalone oscillator from the previous post was to use it as a test tone for this matrix. I was getting tired of using the guitar amplifier and my computer. This is safer and more reliable. No grounding fault from a 9-volt battery has ever killed anyone, at least to my knowledge. And lord knows you can't trust the power grid in these parts...

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When I find a match, I mark the node with its row and column.  Those three in the picture actually are the mouse buttons, and share their own column.  The keys are more complicated and require a letter in addition to a number to be identified.  Right now I have found all the a's.  The keyboard keys make up a 9 X 15 matrix, but not all points in the space are taken.  For example, only A1, A2, A3, A4, A5, A7, A10, and A11 exist.  And they are in no particular order on the board...

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