I’ve started to think about the functions needed for the slider to work well, and how these should be implemented in hardware and software.

Update 2019-05-11: as a later post details, I went a long way down the path of building this: designing a system that would take in all these inputs, and writing code to handle all the events, both intended and unintended. After playing with it, I decided it was too complex, so simplified this considerably.

On startup

Find ends

  • Move to one end til you hit switch, then pull back a little. Set endPoint1
  • Do the same for the other end - endPoint2

Hardware controls:

  • Maybe nothing - just does this when you connect power
  • Or perhaps a reset button to send it to its config state (which just disconnects/reconnects power…)
  • Or maybe there should be a ‘setup’ button. So any motion is triggered deliberately.

Set start and end positions - optional (could just use the two ends)

  • User moves gantry to desired starting point - sets startPoint
  • User moves gantry to desired end point - sets endPoint

Hardware controls:

  • A button for each
  • Plus LED/on-screen feedback?

Set video or time-lapse mode

  • Switch between high- or low-speed ranges
  • Timelapse mode could be quite jerky really - maybe better for photos…

Hardware controls:

  • Switch

Set speed

  • Vary speed continuously across a range,

Hardware controls:

  • Potentiometer could work. Want to read this value once, then ignore input for the rest of the program
  • Ideally with some feedback (even just markings on a dial)
  • Rotary encoder could also work, but would need visual feedback, e.g. 7-segment display or OLED module

Pause and reset buttons

Could be handled with a mode, set in the code. One button press turns it into pause mode, stopping movement, another button press cancels everything….

Power off or reset power

To Arduino etc.

While running

  • Cancel/reset?
  • Pause?
  • Should speed control have an effect if used when it’s running, or should this be isolated to avoid unintentional changes

Other control options

Some other projects use Bluetooth or phone apps. This might introduce some complexity, but reduce the need for physical controls.