Judging from the comments in the last post, this is obviously something that like eight people find interesting, so I just thought I'd throw my mock-up up so you can see what the hell I'm up to.
In spinning around in my office chair, pondering what it was exactly that I needed in a MIDI drum pad trigger thing, I thought it would be redundant to have more than eight actual pads, considering the amount of post-production I do and the actual method I generally use to program drums. In order to use materials on hand (i.e. an Arduino) I knocked that down to six, since an Arduino has six analog inputs, thus obviating any need to do any shift register bullshit just to get an extra two sounds.
I also thought that it would be nice to have a couple buttons for momentary CC. These could be used for any number of things, depending on need, but they'd be handy to have. Since an Arduino has a whole shitload of digital I/O, I could actually have far more buttons, but frankly I couldn't see the need. Three is fine. (I might go to four, but I doubt it.)
So I threw together a quick mockup in 3DS Max, since visualization is 9/10 of creation, and that's how I visualize. That mockup is pictured above. I'm still not 100% sure how I'm going to do the pads, but my thought is thus: using a 1.25" forstener bit, I'll punch divots in the appropriate spots. In this will go a 1.125" rubber grommet. On top of that, a 1.125" zinc or tin disc. The piezo pickup will be epoxied to the underside of this. On top of that, I'll put a 1.25" (or slightly smaller) disc of rubber. In this manner, I'll have a nice surface for tapping, and still maintain good isolation between the pads. Some experimentation will be in order there. I see many methods on the Interwebs, and I've tried a few of them in the past, but nothing for pads this small.
Since the actual unit is a solid block of walnut, it should be dense enough to minimize crosstalk. Again, we'll see about that. I can always program the Arduino specifically for my tapping range in order to get the crosstalk out, so that should be fine.
Today I roughed out the wood, and hollowed out the underside which will hold the electronics. Since this is specific to my needs, I don't need to have it transmit on every MIDI channel under the sun; hence, I'm able to get away with just a MIDI out and a power port when all is said and done.
Fun little project, anyways, while I work up the courage to buy the rest of the shit I'll need for the Jagro.