Starting off with a bang (I let the smoke out)

Well, that was fun. I managed to fry a shift register somehow, and it looks like my Raspberry Pi is out of commission as well. At least I know that each part of the control system works by itself. The interesting part will be getting everything working together; I hope I haven't found a problem with the hardware.

Explanation:

1. I have made a couple of PVC air horns.
2. They can be made in several sizes, from 1/2" ID to 2" and possibly larger if necessary.
3. They can (theoretically) be tuned.
4. I have a few MIDI files for Bach organ fugues that I had arranged for brass quintet.
5. I have a way of controlling the air horns electronically.

Therefore:

     I am building an air horn organ.

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)
• processing made possible by python-midi
• control of a single shift register (mostly) functional
• I'm using SN74HC595N latching shift registers from Adafruit for signal-level output
• control is based on py-spidev
• power control tested, theoretically functional
• ULN2803APG 8-channel driver for power output, supposedly can take 500 mA per pin
• 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)
• learned to solder
• designed and ordered first iteration of the controller PCB from oshpark.

Things to do:

• program control script for the actual output
• test out control boards
• find viable inexpensive valve solution
• revise control boards
• build lots of air horns
• tune lots of air horns
• tune even more air horns
• check complete control system
• devise interface
• final construction

Explanations of the details will follow as I have the opportunity. I'll discuss how the control system works, how the air horns are made, and I'll talk about stuff that goes wrong (or right) as I go along. I'll try to update at least once a week.