Saturday, August 8, 2009

Allen organ project - getting stuff.

I also made a little time to do some rough-cut design for the card reader enhancement, at least enough to order some parts. The idea will be to have an Arduino in a box outside with a keypad and display to do operator interface (or perhaps "organist interface"), and a little box piggyback on the card reader to drive the LEDs.

Earlier posts in this series:

I was going to just put the LEDs in the inboard box, and drive them through a printer cable or some such, but my friend Steve made the good suggestion to run them off the RBBB that he gave me, and have a serial link joining the two boards. There's lots less wire that way.

I have on hand an Arduino (with the LadyAda protoshield), an RBBB (with the PC serial interface), and a suitable 9v wall wart - all also thanks to Steve, who had them as scrap from another project that turned out to be a little too big for them. So I'm tentatively looking at a block diagram like this:

The operator interface will use a telephone keypad for the input. It needs a reasonably large display, because there's a bewildering array of stops, with names like "Trompette en Chamade 8'" that need to be presented. So I'm going with 4 lines of 20 characters, which is the largest that the inexpensive HD44180 controller will support.

I need some reasonably bright white LEDs, 3mm diameter. (5 mm is a trifle too large to go into the holes on the card reader.)

So, significant items on the shopping list are:

  • The LED's - 10 needed, plus a few spares.

  • The display - it looks as if SparkFun's LCD-00256 (actually a Xiamen Ocular GDM2004D) is Just The Thing.

  • A telephone keypad - I've got one in junk, but it's really crappy looking and I'd like the finished project to look halfway presentable.

  • Some suitable connectors for the serial link. I'm also planning to power the operator interface box over those connectors. I'm thinking that a 6-pin mini-DIN, like a computer keyboard, should work nicely. And I've got a spare cable for that form factor.

  • Oh yes, and some bits and pieces that I'm running short on (pin headers and the like).

(And to be honest, I ordered all of this stuff last week, and just didn't trouble to blog about it.)

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