Sunday, December 2, 2012

MKHBC-8-R1 - I/O expansion bus finished.

I am finally getting there. Today I finished soldering the I/O expansion bus. Glad to have that out of the way. If I learned something from this experience, then these pieces of advice should be valuable to any beginner hobbyist using point-to-point soldering technique for their prototypes:

1) A solderable (no need to scratch off the insulation, just apply heat) magnet wire, gauges 30,28,26 makes all the difference when soldering buses (multiple soldering points on the length of a single wire).

2) Rosin soldering paste flux - it really helps that solder to stick to the metal.

3) My choice of sockets for my I/O expansion bus (cheap solder-in-board IDE sockets) proven poor for the prototyping board I use (perforated board with no copper "doughnuts"). After applying heat during soldering the connections, the pins are sliding loose in the sockets, this will not be a lasting solution if I take the expansion boards in and out of these sockets often. Next time I will use perforated and printed (doughnuts) board. I am already thinking of some sort of adapter that I will permanently place in these sockets which on top will have a different board with different choice of sockets or the same kind, however soldered to the printed prototyping board. I am also considering the arduino-like sandwich design for expansion cards.

Here are the current views of the board:

Top of the board. Expansion slots are the black ones to the right. Numbering pertains to the I/O selection lines coming from CPU bus (to the left) through 74LS245 buffers (IC sockets in the middle). The little IRQ connector has IRQ lines of expansion slots connected to it as well as CPU bus IRQ line and also +5V and GND for prototyping purposes.

Full view of the bottom of the main board. The I/O expansion area is on the left.

Closer view of the I/O area I worked on today.

Thanks for looking.

Marek Karcz

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