One of the toughest decisions I had to make in building my arcade cabinet was
how to handle the control panel input. There are tons of different options, from
using an ipac to hacking up an old keyboard, buying a prebuilt panel or even adapting
a jamma interface.



My first interface used a PS/2 keyboard that I laid out in a matrix to avoid ghosting
and hardwired controls to the small keyboard PCB. The keyboard used an 18×2 matrix
and it became apparent very early on that this simply would not work for my cabinet.




If you intend on building a panel with less than 6 simultaneous inputs (ie two
directionals for diagonal, and one button being pusch by both players at the same
time), then a keyboard hack is by far the cheapest and easiest solution to work
with. I will post a separate guide to building this interface.



However my cabinet needed to allow up to 12 inputs simultaneously. Thats diagonals
+ 4 buttons per player. My options were limited to buying an ipac
USB 2 player version ($55 shipped), buying a complete unit like an X-Arcade
($149.99+S/H) or building my own. The ipac is definitely a great device and for
anyone not adept with soldering, I whole heartedly recommend it. But since this
was my custom project and because I wanted independent devices I decided to build
my own USB interface.



For PCB’s I used two Gamez usb gamepads. They can be found for under 10
bucks a piece online, though I lucked out and got them for $4.99 each on a
sale at compgeeks. You can use about any
USB gamepad for this, so check ebay or local friends and you can usually find
them for about 5 bucks each. The key for me was that each controller had regular
dpad inputs + 8 buttons. The other crucial element was no blocking or ghosting,
which these pads avoided perfectly. So this saved me 45 bucks from an ipac, with
most of the features and the luxury of having two independent devices.



The only other item’s purchased came from Radioshack. Two small project boxes,
two 9pin molex connectors, and three 4 pin molex connectors. Total cost for all
this stuff was about 15 dollars. I also picked up two 100ft spools of wire to
hook everything up.



Tools for the Project








1) Soldering Iron

2) Solder

3) Needle nose Pliers

4) Xacto Knife

5) Old AT connector

6) New ATX power supply

7) An ATX female connector and pins

8) Multimeter

9) Wire strippers

10) Dremel

11) Hot glue gun

12) Project Box

13) Molex connectors and pins

14) 2 USB gamepads



The dremel is optional, but it makes cutting the project box a lot
easier and faster. Also you can substitue any kind of epoxy or well bonding glue
for the hot glue, but I prefer hot glue, it holds well and it still removeable
if absolutely necessary.



Getting the Gamepad Nekkid



The first step is to get to the PCB for the gamepad. You can simply unscrew it
and remove the PCB or you have some fun with your dremel and a cutoff wheel and
hack the controller to pieces to open it. I’m sure you can guess the route I took.






Now that we have a nice clean PCB, it’s time to start mapping out our wiring.
If you notice, on this and most gamepads, it uses a clamshell style connection
with a carbon pad. This makes it super easy to solder in the necessary wires.
If you look next to each button, there is a nice big contact point for the + side
of the connection. There is a single common ground per controller, so its super
easy to wire that right up to the ground point. Basically you just connect a wire
to each + point you want to use and wire the single ground. Drop a few dabs of
hot glue to keep those connections in place.








Next up is to connect the molex connectors and fit it into the project box. It
is very important to consider both steps at once, so you can cut the wires to
proper length without stressing any wires to fit the connectors into place or
to have excess wire crowding the box.



I have never been a big fan of wiring up molex connectors, but it’s fairly straight
forward. Clip a pin from the strip,

insert
the wire into the back end of the pin, use your needle nose pliers to crimp it,
then drop a dab of solder on to keep it in there tight.






Repeat for every pin. Then you simply push the pins into the molex connector.
Make sure you have your ordering down before you start this, because it is a royal
pain getting the pins back out if you mess up. I chose to wire Pin 1 as ground
for the 9pin molex (handles the 8 input buttons) and then used the 4pin molex
as the directional positives for the joystick.








I used a couple of zipties to keep things clean, but that’s pretty optional.

*The third molex connector in the picture is for the coin door inputs. I gave
it a separate ground and then a positive terminal for each coin slot. I also reversed
the pinouts for this connector to ensure you couldnt plug in the joystick plug
into the coin door plug.



Next up is putting it all in the project box. About 10 minutes using the dremel
to notch out the molex holes (just used the cut and fit method until they snugly
fit through) and then notched out a hole in the back to match the notch on the
USB controller cord. I had to notch the cover out as well, because it uses an
inner lip.








Lastly drop in the PCB and connectors, then close up with box with it’s included
screws. The result is a sleek and very professional looking encoder box.









Using this method makes creating your cables from the Panel to the encoder super
simple. You need a single negative per player, and then run the positives separately
to the male portion of each molex connector. It makes everything nice and tidy,
and allows you to quick disconnect the encoder from the panel if you ever need
to.