Persistence of Vision Business Card

I have finally achieved an MVP! There are certainly more opportunities for optimization and improvement, for starters:

• Improving the timing and motion detection to stabilize the characters better
• Improving the user interface for more sophisticated functions using the push buttons as inputs
• More sophisticated animations
• Creating a function for updating/adding phrases
• Increasing the character alphabet
  • Current options are A-Z, 0-9, [space], [period], @,!, and ?

Nevertheless, I can get the card to display my website "DTWPROJECTS.COM". Unfortunately, rolling shutter frustrates the effects to a certain extent (I had to pull out an osmo pocket and turn the shutter speed as low as it would go - 24 fps).

I had to work around some faulty issues with the X axis gyro I was sampling to detect up and down motion. I was able to get around the faulty gyro by switching to the Y gyro. It's slightly less effective but seems to work well enough. I may test with another gyro but this iteration should suffice for displaying contact details. It's probably not going to win any prizes but I can now officially consider this a business card :)

I have been very deficient in project logs and now I will suffer trying to capture development history but here it goes:

• Ran into persistent issues with REV 1 board where battery browns out and resets the systems. This was most likely due to directly driving LEDs from ucontroller outputs with no resistance to limit current (I'm aware this is generally bad practice but I wanted to get blinkin' quickly- I paid for this with the brown outs)
  • This wasn't an issue when board was powered through Arduino 3.3 V pin which was fine for development and testing but made it difficult to test persistence of vision with all the cables hooked up
  • More than once unplugged cables which were supplying power and providing debug info through arduino serial. Also fatigued a couple cables 
• Spun a second revision of the board with 800 ohm resistors to limit LED current.
  • Battery test indicated that coin cell can easily handle reduced load
  • 177 mA max current with rev 1 board - All LEDs on. brief research suggests coin cell will be drained in about an hour (abismal)
  • 30-40 mA max current draw with rev 2 board - 8 hours of continuous operation (significantly better and definitely overkill)
  • Regarding power: i've identified a need to incorporated sleep functions into ucontroller and accelerometer to increase battery life
• Ran into problems with GY-521 boards
  • no telemetry on some
  • registers returning all zeros
  • so far investigation suggests either ESD or damage from accidentally applying 5V. incorporated practed
  • 4 boards useless so far
    • current board won't populate two largest bits on Z acceleration which is unfortunately the more pertinent metric
    • Mitigating by examining X-axis gyro for now
    • ordered more boards to further investigate (maybe I'll get one that works without issue)
    • rev 1 board works flawlessly but has been soldered in (not gonna risk removing as rev1 is my backup for development)
• Need to post video of test but rolling shutter issues limit the effect

Added a couple photos of a second revision: the original design powered the LEDs from the atmega pins directly with no resistance- this was causing the device to brown out under coin cell battery power. New revision adds about 800 ohms after the LEDs to reduce overall current consumption. Tests indicate that the coin cell ought to be able to provide enough power under this configuration. Finally, no longer constrained to test under the tether of supply wires!

I had intended to submit project to Hackaday after working out some hardware kinks and finishing software. I wanted a functional minimum viable product before even creating the hackaday.io page. I expected to submit just before the deadline. This is my first Hackaday contest and wanted things to at least work before submitting.

Was listening to Hackaday podcast and Elliot mentioned he can't wait to see one of the submissions "start working". This reframed my mentality about project submissions- figured I'd try to get stuff in and get it working later.

I have almost no practice documenting my own projects and want to get better. Creating the .io page is a good start but I have cold feet before completely submitting (still want things to work). Will use .io page to practice documentation and project logging and plan to submit once I have updated with a minimum viable product- this is a step in the right direction. Updates pending soon (the clock is ticking!).