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Cut Down Keyboard

What the ...?

Sometimes, a big, fullsize keyboard is a hassel. And sometimes, a custom keyboard made from little buttons and connected to a parallel port is a hassel. And sometimes using a microcontroller is a hassel, too.

And those small, custom keyboards cost so much, too!

What I wanted was a small keyboard, to control a fileserver of mine. I wanted something that was easy to interface and program with. The easiest thing to program with is, naturally, a keyboard.

So, I made a small keyboard. I knew what I wanted to keep, so I mapped that out. A friend and I made a day of it to make two keyboards from three others.

We started with three keyboards. Disassembling these revealed one keyboard that was made from buttons soldered onto a PCB. The other two contained a small controller board and then a thin plastic matrix thing. So, we took the buttons from the PCB keyboard (because the controller components were all over the board, making it rather difficult to cut down), and took the controllers from the plastic matrix keyboards.

Before we completely disassembled the plastic matrix keyboards, we mapped out what keys connected to what pins, on paper. We then got a piece of veroboard (a PCB with lots of holes, and tracks running along one dimension) and soldered all the keys we wanted, in the fashion that we wanted.

After that came the fun part... attaching it to the controllers. Some nice hookup wire was used for this... and after some mucking around, we had ourselves two little keypads.

Powering up the keypads resulted in a partial failure. Some keys worked, and some didn't. After some checking against the drawings we made, we found that some connections were wrong. But, never fear, a few touches with the soldering iron and we corrected those errors.

Pictures of the result

Here are some pictures of the final result. I only have pictures of the little keypad I kept, and not the other one. Also, I don't have any "during" pictures, because we didn't take any. All I can show is the final result.

The finished keypad


A top view of the keypad.


This shows how I connected the keys to the board.


Look! Zilog made the controller!

What did I use it for?

I used it on my fileserver. See this page for information about what I did with it...

Building your own

So you want to build one too? Well, here's a few hints...

• Have a keyboard that you know you want to disassemble. As soon as you disassemble it, it will probably never work again. Keep this in mind.
• Decide what buttons you want, and have them handy. (Not just the "keys" you want (Home, End, Cursor, etc) but the physical buttons that you want to press.)
• Have some veroboard ready, although there is no reason why you can't make your own PCB.
• Keep the keycaps - you'll need them, unless you want to write the function of the keys with a black marker.
• The LEDs on the board might not be where you want them. Feel free to move them, but do so carefully! (I kept mine in the same place, but my friend moved his.)
• I got lucky with my controller board, in that the board was connected to the plastic matrix with a connector, which I unsoldered and used the holes to connect my keys. My friend was not so lucky - his had an edge connector which simply pressed against the plastic matrix. In the end, we soldered the wires to pins on the microcontroller. But make sure you think about this one carefully!
• We used keyboards with AT interfaces -- the large, 5 pin DIN connectors. I initially used an AT-to-PS/2 to connect it to my fileserver, and this worked very well. Around August 2004, the PS/2 keyboard port on my fileserver failed -- and I bought a USB-to-PS/2 adapter, which I connected to the AT-to-PS/2 adapter. The whole arrangement works very well. So don't worry about how old the keyboard is -- you'll get it hooked up somehow.

But other than that, have fun. If you make one, send me some pictures - I'd be interested to see what others did with theirs...