This Instructable will hopefully help you get started solving those problems.
Step 1: Materials and Tools
- keyboard (I used a Dell Multimedia Keyboard that was missing some keys)
- container large enough for keyboard circuit board (I used an old Tupperware container)
- 1/4" headphone jack (one for each key you want to be able to use)
- a few short wires (I used strands from solid core Cat5 cable)
- foot switch(es), or other (momentary, normally open) switch, such as this
Utility knife (or similar sharp instrument)
Handheld rotary tool (optional)
Step 2: Disassemble Keyboard
The keyboard I used has a circuit board for the keyboard portion as well as one for the attached USB hub.
Step 3: Drill and Cut Appropriate Holes and Slots
For my build, I wanted to be able to make use of the USB hub as well as the multimedia buttons on the circuit board. This meant that I had to cut slots in the side for the USB ports, and drill holes for the buttons.
To get the locations of the buttons I scanned the circuit board, printed it at 100%, and taped that to the lid as a template for drilling. It probably would be easier to use a photocopier, but I don't happen to have one in my workshop.
Step 4: Solder Wires
Determine which combinations from the two sets of pads will trigger the appropriate keystrokes. You can do this either by tracing the connections on the plastic that sits under the keys, or by connecting it to a computer and systematically connecting pairs. On this keyboard I believe it was F and 1 that triggered a PgDn keystroke, and H and 1 that triggered a PgUp. Again I'll refer you to randofo's Instructable for more information.
Scrape off the black stuff to expose the copper underneath that you can solder on to. I usually use a dissecting microscope for small soldering, but this should be big enough to see fine with your naked eyes.
By naked eyes, I don't mean to discourage the use of safety glasses.
In my build, I soldered the "sleeves" of the jacks together and then soldered one of them to the wire that connects to "1". I then soldered the wires from "F" and "H" to the tips of the respective jacks.
Step 5: Attach the Electronics to the Case
You may be able to use some of the screws that originally held the keyboard together in order to mount the circuit board, or you may just put everything inside the box and not worry about having buttons poking through holes in the box.
Close the lid and admire your handiwork.
Step 6: Uses
- control PowerPoint while keeping your hands free
- allow students with limited dexterity to interact with the computer
- use more limbs for computer gaming (e.g. throw grenades with a foot switch)
- control sheet music display in a pdf viewer (thanks caitlinsdad)