the project

I am building a MIDI-controlled air horn organ.


  • controlled by a Raspberry Pi A+
  • MIDI-based with possibility of human input as an extension
  • 64-note range

Progress so far:

  • MIDI files can be processed using python in order to track what notes should be sounding at a given time (data point at each note-on or -off event)
  • control of a single shift register (mostly) functional
  • power control tested, theoretically functional
  • miswired something and fried one of the shift registers and the RPi2 that I was using to test
  • determined that there are no HDMI cables in the house to hook up the RPiA+ to the TV
  • determined that my WiFi adapter won't work with Raspbian (OS on the Pi)
    • got functional WiFi adapter
  • learned to solder
  • designed and ordered first iteration of the controller PCB from oshpark
  • tested version 1 control modules (3x)
  • eliminated one possibility for solenoids as non-viable
  • refined and ordered final version of control PCB from oshpark
    • noticed that I forgot to correct silkscreen when I moved one of the headers
  • found another source of solenoid valves at a relatively reasonable price
  • designed an optoisolated interface board
    • safety!
      • ish
  • assembled final version of control PCBs
  • determined that the aforementioned solenoid valves have insufficient airflow
  • designed pneumatically-operated gate valve
    • laser cut design
    • cheap (if it works)
  • realized that I shouldn't use 28 gauge wire for running the common positive for the solenoids
    • decided that it would probably be good to just shell out the $15 or so for the 9-position connectors to rig for connecting solenoids to the control boards
  • acquired a regulator
  • reconstructed CAD files for gate valve
  • preliminary testing of gate valve completed
  • keyboard layout selected
    • chromatic button accordion layout
  • keyboard panel laid out and cut
    • wore out two hole saws
    • they're dead, Jim
    • failure to chooch
  • keyboard panel assembled
    • don't ask me to change it
      • I won't do it.
  • input PCBs designed and built
    • I messed up the first time
    • they should work now
  • keyboard rebuilt
    • new panel using 1/2" MDF
      • cut on the ShopBot
    • properly-spaced buttons so it's easier to assemble

Things to do:

  • design keyboard interface modules
    • partially finished
  • build lots of air horns
  • tune lots of air horns 
  • tune even more air horns
  • check complete control system
  • devise interface
  • final construction

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