2015-09-12 (Sa) Wrist Mounted Chording Keyboard

Over the last few days you may have noticed the lack of work on the moving parts. Once everything was assembled I tried holding the whole contraption to my wrist and pressing some buttons. I was sad to notice the pressure needed to hit all four buttons simultaneously, which happens often, would push the keyboard away and it felt flimsy. Not cool.

During the days when I wasn't working on the motion I turned over ideas in my head of how to eliminate this problem. I considered magnetically latching the keyboard to my palm, using capacitive touch sensors instead of buttons or replacing the buttons with ones which took less pressure. Ultimately I decided to redesign the keyboard with one that aligned the force of the finger key presses with the force of the thumb key presses. In other words I squeeze the keys like a stress ball instead of pushing down like a traditional keyboard.

This decision wasn't easy because I like how cool the moving arms looked but I really want to finish this project and a functional keyboard is better than a cool-looking non-functional keyboard. I refuse to make this merely a prop, it will work.

Enough background.

The button configuration had a severe flaw where the user pressed down on as many as four buttons at once which was in direct opposition to the direction the servos move. The servos may have had enough responsiveness and torque to counteract this pressure but it was an unreliable design.

Folding key levers had a very attractive look and the movement when they deployed would draw attention. Unfortunately the moving parts added complication to a project which needed to be finished soon

Existing keypad design was abandoned and a new design was conceptualized. Key levers and buttons were replaced with buttons which would be pressed directly. A soft prototype was mocked up by pressing switches into an eraser. More space will be necessary to achieve the standard key spacing for the fingers but the thumb switches, which were touching on their sides, were spaced well and two could be pressed simultaneously with ease.

Soft prototype of seven buttons

Prototype held in typing position

Prototype on top of existing keypad

Pencil sketch of design for keyboard enclosure

A modeled holder for the switches will have to include raised portions where the user can place the thumb and fingers and keep pressure without pressing any buttons. On the thumb side

Downloadable Files:
To do:
  • Wrist mount
    • Revise offset levers 
    • Make holes in thumb board cylindrical instead of countersunk 
    • Add limit switch mounts
    • Connect servo arms
    • Lengthen servo arms
    • Integrate:
      • Controller
      • High precision potentiometers for tuning servos
      • Servos
      • Enclosure for each controller
      • Limit switches
      • Activation switch
    • Debug 
    • Test
    • Refine
    • Repeat
    • Activation switch
    • Route wires 
  • Write instructions
    • Compress and link to all files
      • OpenSCAD files
      • STL models
      • Arduino code 
    • Make diagram with everything labeled 
    • Schematic for servo controller

The rest of the posts for this project have been arranged by date.

First time here?

Completed projects from year 1.
Completed projects from year 2

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2015-09-10 (Th)