I hear you! Below is a long answer, short answer is "you just hook switches up to the board with some wires, and the computer thinks it's a keyboard." And they are programmable, so you can get pretty much any keys or key combos from it!
(You might have to use something like AutoHotKey to get combos and full multi-key macros, but still, works great!)
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The I-Pac is a "keyboard encoder" - basically the electronic guts of a usb keyboard, specifically for gaming. Here's the creator's pictures and description:
http://ultimarc.com/ipac1.html
You wire up a bunch of switches (buttons, keys, etc.). Each switch has 2 wires that connect to it, a common ground wire that attaches to all the switches, and a wire from each switch to a "key" connector on the I-Pac. When the switch is pressed it just connects the two wires, and the board sends a keyboard key to the computer. As far as the computer is concerned you've built a custom keyboard with funny looking keys. These keyboard encoder boards are customizable so they can send any keys, so you aren't really limited to which keys any more. (The really old boards weren't programmable, so you probably want a modern one.)
The keys can be actual keyboard keys, arcade buttons, the 4 directions on an arcade joystick, or really anything that will "connect" the signal wire to the ground wire when you activate it. Then you find a way to lay it out - drill holes in an arcade control board for buttons, or put keyboard keys on an electronic project board, or 3d print a custom panel with holders for keys; then slip the buttons or whatever in the board, and wire them up to the I-Pac, and plug it into a usb port!
I-Pac connects the wires to the board using screw terminals, so you slip a larger size wire (the very common "project wire" from Radio Shack or Amazon or DigiKey or wherever) in the little hole and use a screwdriver to clamp it in place.
Mini-Pac does exactly the same job, but instead of screw terminals to hook up "large" wires, it has a connector that you hook up a "wiring harness" (comes with or buy from same place) of much smaller wires that easily slide onto standard switches/buttons - or you connect a ribbon cable between it and another electronics board. Mini-Pac is a newer product, and can be a lot easier for small projects like an arcade control panel or a keypad - but it's a little less flexible if you are running lots of project wire around or have custom buttons instead of common switches.
(In fact, there's a u-hid product from ultimarc.com that's newer and smaller than the Mini-Pac! Same idea, a little more complexity of configuration.)
And there are lots of other similar keyboard encoder boards, I just really like the ones from ultimarc.com after using them for years.
Here's a link that shows a closeup of the arcade style switches - "Cherry brand microswitch" - and how they are used in arcade joystics and buttons. You just hook the common ground wire up and the "normally open" wire up to the board, and that's all there is to it.
http://forums.shoryuken.com/discussion/ ... nes-to-buy
There's lots of
google images on the keyboard "key switch" for macro pads and custom keyboards. Those links explain how they work in detail, but basically they are made to put on a flat surface (like an electronics pcb or project board) next to each other like a keyboard and you wire up the same ground common and normally open connectors.
And once you've got that - two wires connected to a usb keyboard encoder - you can hook up any kind of switches. Car parts, airplane parts, electronics, industrial switches, steampunk stuff, custom "buttons" made with a 3d printer or in the wood shop - anything that will connect the two wires together to "press" the keyboard key when you active it! Arcade joysticks are just 4 "arrow key" buttons pressed when the stick moves that direction, and it pushes 2 arrow keys for diagonals.
And they also have similar USB
boards to control LED lights (but I don't have any experience with them), and of course there are all sorts of buttons with lights inside them, and so forth.
All that to say, I'm not that great with general electronics, but this is sort of electronic Legos - buy the board, some wires, and the buttons (joysticks, etc) you want, and plug them all together to get custom keypresses to the computer to use in games! Works fantastic, between the custom keys necessary for flight sims, Mame, and so forth. (And real keyboards do funny stuff to keep expenses down, so it's much harder to just run wires from a button into a real keyboard; these gaming keyboard controllers are much better.)
Here's a link to some arcade sites I've bought buttons and controllers from.
Arcade hobby sites:
http://ultimarc.com
http://groovygamegear.com
Real arcade joystick & button & more manufacturer:
https://na.suzohapp.com/products/arcade_game_parts/
I know flight sim enthusiasts are as crazy cool as arcade people:
Here's a great cockpit project that looks like a crazy 10x version of the arcade control panel's I've made:
http://simhq.com/forum/ubbthreads.php/t ... Freelancer
and lots more:
https://www.google.com/search?q=custom+ ... h&tbm=isch
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And there are also similar boards if you want to make or hook up FlightSticks and rotary dials and other stuff like that. Slightly more complex than the buttons, but similar ideas. They just make the custom items look like a mouse or a gamepad/joystick to the computer. That's how people hook up spinners and real airplane parts, etc., if they aren't just clickable buttons.
