Today I did a test build-out of the CTC machine short right side panel. There were a few annoyances but nothing insurmountable.
The cutout at the top is where the aluminum model board will attach. In the rear view, the top white connectors power occupancy lamps on the model board. There will be a bit of untidiness as individual model board LEDs may be a couple inches to one side or the other of the column board that provides power.
Wire management seems to be working out quite well. If we had used a conventional CMRI motherboard with DIN and DOUT boards, there would be over 500 point-point wires running all over the place behind this short panel and the 5 foot long main panel. With CMRI hardware, it is also necessary to solder LED resistors directly to the LEDs, as there is no home for them on the DOUT boards. Likewise, to “pulse stretch” a code button press, it is common to epoxy a large electrolytic capacitor to the panel next to the switch, and hang a resistor in the air between the switch and the pushbutton. Most of those wires would need to make a “home run” connection to the CMRI DIN or DOUT boards.
Thirty-two PC boards, one for each live column, eliminate about 300 of those wires. The remaining wires are short and connect directly above or below the boards. Along the bottom of each board is a currently unwired connector. For each set of 8 PC boards, a single CAT5 network cable will daisy-chain horizontally to carry power and an I2C communications bus. Essentially each of these cards acts as a wire “funnel” to the CAT5 cable. That cable then terminates at an Arduino-powered PC board that replaces the CMRI motherboard, DIN and DOUT cards. For 32 boards, I need 4 CAT5 cables.
The PC boards also carry all the LED resistors. By programming the Arduino to be notified by interrupt whenever a switch changes, there is no need for code button press stretching capacitors.
Because each board has 16 individually-programmable input or output pins, there is a maximum “capacity” of 512 switch inputs and/or LED outputs. That’s more than enough.
All-in-all, except for a few mistakes I made, I’m rather pleased with how this is shaping up. It looks particularly good when powered-up by a Sparkfun Arduino Redboard used as a test harness. In person the LEDs are many times brighter than in the photo. During an 8 second exposure they were illuminated for only about 1/2 second.