For the interface, I went with the KE72-T keyboard encoder from Hagstrom Electronics. I chose the KE72-T for a few reasons:
So the KE72-T it was.
I told you that I'd get to this.
The goal is to connect the switches on the buttons and joysticks in the control panel to the pins on the KE72-T. I went through a couple of ideas before deciding to use D-SUB solder-type connectors from Radio Shack. I figured that the D-SUB would provide a nice secure fit, but one which could be disconnected fairly quickly if I wanted to make a second swappable control panel. The possibility of making a swappable panel is also why I mounted the KE72-T inside the cabinet versus in the control panel box itself.
Each of the four cardinal directions on the joysticks has two prongs coming out of it. It doesn't matter which one you think of as the "lead" and which one you think of as the "ground" on the Wico leafswitches because the principle is basically the same: when the connection between the two contacts is closed, that particular signal will be sent to the KE72-T. All of the microswitches in the pushbuttons work essentially the same way as the leafswitches in the joysticks, except that the microswitches do have a specific contact labeled as "ground" and one labelled as "N/O" (or "normally open").
Eight of the 80 pins on the KE72-T are "ground" pins, so all you have to do is make sure that:
All of the ground pins coming off of all of the buttons and joysticks eventually come to a 4-pin terminal block mounted underneath the control panel. This was basically done to reduce the number of ground wires coming from the panel from 25 down to 4. It doesn't matter which ground pin on the KE72-T that you use, so I just combined all of the ground wires into four wires. These four ground wires then end in a 9-pin D-SUB connector.
The same basic principle applies to all of the "lead" wires (except that I wasn't able to reduce and combine them, obviously). All of the lead wires end in a 25-pin D-SUB connector (for the 1P and 2P controls) and another 9-pin D-SUB (for the other "misc" buttons on the control panel).
The pictures should hopefully explain what I'm talking about.
The KE72-T has two separate groups of 40 pins, each in 2 rows of 20. The easiest way to connect wires to these pins is to use an IDE hard drive ribbon cable. I originally was going to have the ribbon cable connect to a terminal block, and then have wiring run from the terminal block to the D-SUB connectors, but that kind of seemed like an unnecessary extra step. I just stripped the individual wires from the IDE ribbon cable and soldered them directly to D-SUB connnectors.
I also have a second 8-block terminal block connected to the second set of pins with a separate ribbon attached to the KE72-T. This is for the "odds-and-ends" keys that aren't part of the top control panel: the buttons on the front of the control panel, and the coin door switches.
Again, see pictures for more detail.
Oh, and I used 22 AWG solid wiring for everything.