Piano Automation – Valve Control Board Build and Test

Last weekend I got around to populating and testing the piano valve control board. Unfortunately it did not work when initially powered on, I was able to track this down with a scope to problems with the level shift circuit between the pi and the shift registers. Rather than troubleshoot this farther I ended up re-designing and re-etching the board to replace my transistor array level shifter with an off-the-shelf level shifter sub-board. I also took this opportunity to #1 redesign the solenoid wire connections so that a pin header connection could be used rather than having the wires directly soldered to the board and #2 add a connector to the edge of the board to use the pi’s pin header connection.

In the mean time I had also created a 3d printed enclosure to hold the board on the back of the valve bank. This was important as it allowed the final solenoid wire lengths to be determined and I soldered all the solenoid wires onto a pin header. I also 3d printed a support ring to stabilize the pin header and hot glued it all together to act as a single strain relieved connector.

This weekend I was able to finish and test the re-design. All channels seem to be working OK and I’m able to control the piano keys individually from a tablet using a python script. I have some python scripts working that successfully decode the MIDI files, but I haven’t connected the dots between this and the hardware yet, that’ll be the next step along with hopefully adding a web interface.

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