Low Voltage Warning UI Prototype

In my last entry about the low voltage warning device, I said that the requirements have changed.  Among other things, the device has to have a green LED active when the voltage is OK, and the LEDs have to be dimmable.

Based on the new requirements, I think that a microcontroller is justifiable.  I have no doubt that this could still be done without one, but I like microcontrollers, and that's where my experience lies.  I plan to use one of the small AVR uCs which are under $1 in quantity.

The device will now have to have both a bi-color LED and a single button.  This single button will have to both toggle the state of the LED and allow for dimming.  I think that this calls for a UI prototype to see how well this works.

As a side note, I'd much prefer a lit button, but all that I can find are prohibitively expensive.

This is how the button and LED should interact:
  • While in the normal (voltage good) state, pushing the button should toggle the green LED on and off.
  • While in the low voltage state, pushing the button should toggle between flashing orange and solid orange.
  • In any state, holding the button down for a few seconds should start dimming the LED.  When the button in released, the LED will maintain this brightness.
  • If a low voltage state occurs, the LED should always go to the flashing orange mode (as opposed to solid orange) in order to catch the attention of the operator.
For a prototype, I glued a couple of switches, an LED, and an Arduino to a piece of cardboard.  Rather crude, but it works.  Here's a video demonstration:

LVW UI Prototype from James Wilkins on Vimeo.

Sorry for the poor video quality.  My camera just died on me today, so I had to resort to a web cam for recording the video.  It was either that or a cell phone, and the cell phone would have been worse.

I think that this will work.  Of course, I'll have to run it past some actual users to see if it proves too confusing.
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