Hello:

     My partner and I are experimenting with MIDI-controlled
     direct electric solenoid (i.e., no air) percussions.

     So far, we have successfully prototyed a controller
     based on an Arizona Microchip 17c42 that activates
     solenoids arranged to deliver a percussive blow.
     Photo-SCRs isolate the TTL outputs from the 17c42
     and switch the full-wave rectified (but unfiltered)_
     AC for the solenoids. (If we filtered it, the
     SCR could never turn off. We don't seem to hear
     any significant "buzzing" because of it.)

     We're I'm decoding MIDI in a slightly non-standard way.
     The velocity byte is used as the amount of time, in increments
     of 2ms, that the solenoid is on. Note off is ignored.
     (I plan to implement some "drum roll" pairs of outputs
     that will be switched on/off with the MIDI note on/off
     commands, and the repeat rate/duty cycle contolled by
     the velocity byte.)

     My problems now are mechanical. I have the software and
     electrical engineering skills, but don't have the
     mechanical knowledge (and tools!) to properly construct
     the mechanical aspects of these devices to make the reliable.
     We have jerry-rigged some mechanicals, and have a solenoid
     arranged to push a rod onto a small drum.

     If someone in the SF bay area would be interested in
     collaborating with us, or would like a copy of my
     software for the 17c42, please send some email. I plan
     to have some PC boards made for the controller once
     the circuit is finialized; this may turn out to be
     a lower-cost alternative to other MIDI-to-switch
     decoder products.

Robert A. Swirsky¶
swirsky@adobe.com