2015-09-22 (Tu) Wrist Mounted Chording Keyboard

Servo programming was written for an Arduino Pro Mini by lifting the code previously used for the Digispark. Without the ability to get serial feedback data it was unnecessarily difficult to debug. Servo control relies on precise PWM timing and using numeric feedback from the controller allows easy confirmation that the correcting timing is being used. Digispark required the data pins for this project so feedback was not possible with every I/O attached plus it required another library and unique terminal-style program.

This is another perfect example of a time when breadboarding would have me saved time.

Desoldering was done on the terminal board so it could be reattached to an Arduino Pro Mini. Pull-up resistors were no longer necessary so they were removed and discarded. Programming was changed to reflect this; Digispark, with an Attiny85, did not support the pull-up resistor function while the Arduino Pro Mini, with an ATmega328, supported it. This reduced the hardware necessary and would make rebuilding or copying the hardware simpler.

Arduino Pro Mini to replace Digispark

Pro Mini soldered to terminal board

After the necessary soldering work the device was powered and programmed. Testing for the device was powered from a USB battery through a programming board. Servo control was not perfect but debugging should be substantially easier. A video was taken of the first try. Some of the problems include jerky movement and unreliable switch reactions. A power connector will have to be attached.

First attempt at servo movement with Arduini Pro Mini

Downloadable Files:
To do:
  • Wrist mount
    • Make longer straight servo arms
    • Make base for keyboard
    • Integrate:
      • Controller
      • Servos
      • Enclosure for each controller
      • Limit switches
      • Activation switch
      • Power connection
    • Debug 
    • Test
    • Refine
    • Repeat
  • 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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2015-09-22 (Tu)