Direct solenoid control of percussions
By Robert Swirsky
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
Robert A. Swirsky
(Message sent Tue 22 Aug 1995, 02:07:28 GMT, from time zone GMT-0600.)