October 7, 2010

Pedalboard wiring plan

Now that the pedalboard MIDI encoder is on its way, I am thinking more about how exactly to wire the contacts. In the original installation, this pedalboard's contacts were all connected to a bus wire. A cable ran down the length of the contact rail, with seven connections for each note, presumably for all the to-pedal couplers.

Being that the MIDI encoder uses a scanmatrix, a single bus wire won't work. I was thinking of repurposing the bus wire by cutting it into eight-note sections (1-8, 9-16, 17-24, 25-32), which would work with the scanmatrix. On the other side of each of the switches is a diode, and the diodes are connected together 1-9-17-25, 2-10-18-26, etc. Napkin diagram here, schematic here. (Electronic convention is to start with zero, but perhaps this will be easier for non-electronic-folk to understand.) I've seen others wire the diodes together directly on the contact rail, but I'm afraid this will be difficult to maintain and unwieldy, and just plain esthetically bonkers. (I seem to have picked up an ethic of esthetics back when I worked with professional organbuilders.)

So, at this point, I am planning on running a 50-pair CAT3 cable along the contact rail, and using a pair for each note - that is, leaving the bus bar out of the equation altogether. The CAT3 will be routed out of the pedalboard, connected to an intermediate wiring board of hackery inside the "console," which will sort out the scanmatrix and in turn be connected to the MIDI encoder. (mwahahaha!!!)

I believe this will lend itself to maximum maintainability, flexibility, and beauty. The pedalboard will be a freestanding unit with a generic, detachable cable; the board will sit safely inside the console without having to ride around on the pedalboard, introducing either the risk of being kicked or the need to construct an auxiliary enclosure on the pedalboard. I don't anticipate having to swap out pedalboards, but if I did (hmm, maybe a flat 30-note for a Baroque virtual organ??) it would be easy to do while still using the same electronics installation.

Update: D'oh... the cable I ordered was 25-pair, which seems to be the standard available prepackaged cable with connectors. Ergh... back to the drawing board! Perhaps I'll cut the cut bus wire and hook it up to the cable, and use the external wiring board for the diode side only. That makes sense... and it will only use 40 of the 50 wires. Phew!

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