For several years I suffered when using ready made computer

pointing devices. Here are some of the solutions I came up with.

Unfortunately it did not prevent carpal tunnel injury, it just delayed the inevitable.

hand_small.gif (25407 bytes) I had carpal tunnel surgery because my fingers tips were "going to sleep" and  I needed other surgery.

Computer Mice

As an input device the Mouse seems harmless enough, but if used for several hours each and every day, the effect of "clicking:" the buttons can cause Repetitive Strain Injury.

Throughout the years I have adapted various mice to suite my particular requirements and here are some of the results.

There are many good foot pedal switches on the market (see my links page), however I was lucky to find these old

three pedal switches and with a little work they function real well.

Mouse_1.jpg (10650 bytes)Early Serial Mouse with foot pedal adapter.

Using extra wires in the mouse cable, it was easy to parallel the foot and mouse switches.

In the above photo I labeled the left button "middle" that's because it was more convenient to use the large switch for the "Left" mouse button.

As time moved on, serial mice became long in the tooth and there was a clear need to improve the design.

Mouse_2.jpg (14542 bytes)Infrared Linked Foot Pedal.

I wanted to get rid of the direct connection and decided to link the foot pedal to the mouse by Infrared link.

Mouse_4.jpg (14934 bytes)Inside of the Infrared Linked Foot Pedal Mouse.

The 38KHz Infrared receiver is wrapped in aluminum foil to block the IR from the XY mouse switches.

The light guide takes the path highlighted in white, from the IR receiver around the mouse to the point of exit.

Electronics mounted on a small circuit board and held in place using double sided tape.

Power is taken from the mouse.

9812-03.gif (9413 bytes)Receiver Circuit

The IR data stream is 8 bit ASCII and I used  "L" for left "R" for right and "M" for middle.

The PIC16F84 runs at 38KHz and effective Baud rate for transmission is 300 Baud.

These bytes are decoded in the microcontroller and applied to the existing mouse circuitry.

Double click is done by the microcontroller.

Mouse_5.jpg (14705 bytes)Infrared Foot Pedal Transmitter.

Three IR LED's transmit the data. The LED's are placed at angles to cover a wide area.

Notice the very simple but very effective switch debounce circuit !.

The 38KHz oscillator is used to modulate the 8 bit data stream..

Range is about 4 feet.

9812-01.gif (11837 bytes)Transmitter Circuit.

Zero Mechanical Switch Mouse

Mouse_6.jpg (11970 bytes)Zero Mechanical Switch Mouse.

Here I decided to remove the existing Microswitches and replace them with proximity switches.

It works very well, but has one drawback. It requires the user to keep the fingers away from the

proximity switch to NOT operate the switch. Although zero force is required to use the switch, it is uncomfortable to hold one's finger above or away from the switches.

This mouse has been retired.


Mouse_7.jpg (11466 bytes)Lever MicroSwitch Left Button.

Looks horrible, but the microswitch requires very little force to operate.

This is my everyday mouse, it is the second one, the first one did several thousand miles before it was retired.

No Click Microswitches

Mouse_8.jpg (17746 bytes)No Click Micro Switches.

These special modified miniature lever Microswitches only require about 15grams to operate, and have "no click".

It works fine and I use it on a daily basis on my second computer.

I have plans to add a Microcontroller to this design, for two reasons.

1./ To improve the debounce.

2./ Add a Click Sound.

A typical microswitch as used for mouse buttons requires anywhere from 50-75grams of force to operate, and makes a mechanical click that can be heard and felt!.

Mouse_9.jpg (10042 bytes)Typical Mouse MicroSwitch.

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Copyrightę 2005 Hans Wedemeyer, Houston, Texas, U.S.A. All Rights Reserved.