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Step 1: Components and tools
PVC architectural plastic sheet for foot board, 1/2 inch thick (actual 0.470), 17 inches by 22 inches, chosen because it is slick and because I had some scraps.
1 optical mouse; Targus model PAUM004U because it was on sale nearby for $10; reconditioned ones are available for that price via the internet.
2 roller lever switches, Radio Shack #275-017A, $4 each, order or find walk-in store that stocks them at radioshack.com.
7 feet clear plastic tubing, 1/2-inch inside dia, 3/4-inch outside dia.
Screws for fastening tubing to foot board, 1-inch long #6 phillips pan head, and washers.
Woodworking tools. If motorized tools are used on plastic, they should be run at very slow speed.
Step 2: Background
The mouse is oriented the same as if used conventionally, with its wire tail aimed away from the user, but rolled over belly up. Sliding the foot left causes the pointer to move left across the screen, and sliding the foot forward causes the pointer to move down. This latter may be disorienting for some users, and the vertical movement can be reversed using the mouse control setting offered by some operating systems. You can also download Sakasamouse, which will allow you to change the direction of either or both mouse axes, and restore them, anytime you wish http://hp.vector.co.jp/authors/VA026826 . I adjust the pointer speed to the lowest setting.
I operate my footmouse with slippers that slide easily because their plastic soles have become slick with use. The same effect could be achieved by pulling XXL size men's cotton socks over slippers or even street shoes (You know what they say about men who have big feet. That's right, it means they have big socks). Size of the foot board and locations of the elements depend on the size of the user's feet and their comfortable rest positions.
Step 3: Foot board layout
Step 4: Foot board openings
photo 1: With switch located at correct depth in this material, tops of switches' mounting holes align with bottom surface of foot board.
photo 2: Location of a slot and its axes marked on tape
photo 3: Material is removed by drilling
photo 4: Slot is cleaned up using Dremel tool with spiral bit and router attachment. Wood blocks cut and sanded to length define the width of the slot as 0.25 inch, for a sliding fit with the switch, and the distance between them defines the slot's length at one inch. I filed down two small pips on the sides of the switches to make them even with the bosses that surround the switches' mounting holes.
photo 5: The upper edges of the slot are rounded over using small flat and round hand files.
photo 6: The opening is drilled and the plug sawn out then it is cleaned up using big-boy router having speed control, spiral bit and pattern-following collar. For aesthetic reasons I had hoped to install the mouse in a recess in the bottom surface of the foot board, with its magic navel peering up through a small opening. This did not work because the foot must be very close to the mouse's tummy to engage the optical pointer control. I did not make provision in the opening to accommodate the rubber plug that provides strain relief for the mouse's cord, I just stuffed the entire plug up the mouse's wire hole.
Step 5: Mouse modifications
photo 2: The cord reel can be discarded if desired by removing a screw and prying it open.
photo 3: Excess plastic parts snap off of the cover.
photo 4: Two1/4-inch dia hex-head bolts, one-inch long, washers inside and outside, fit through existing openings, the square one drilled to size.
photo 5: Bottom of the circuit board shows the two outboard solder connections of each click switch. A length of stranded hookup wire is soldered to each. Switches may be left in place, but I unsoldered and removed both, plus the scroll wheel switch, for possible use in another project.
photo 6: Scraps of the foot board material aid bending two mounting brackets from sheet metal strip 1 inch wide, 0.080 inch thick. The brackets, shaped with the mouse assembled, will position the mouse's magic navel just below flush with the foot board's upper surface. Lock washers and nuts attach the brackets to the mouse's cover.
Step 6: Switch mounting clips
Step 7: Assembly
My foot board sits higher than it needs to, but I could not resist these white metal door stops for legs. Prying off the rubber tip reveals a screwdriver slot that aids in installation. I pre-drilled holes in the underside of the board, without going through, partially screwed a doorstop into each hole to create threads, then backed it out. I then ground the tip off the auger of each doorstop so they would not go through the foot board, then screwed them snugly into place.