Prototype 1: A Lesson In How Not To Multiplex EM Displays

A project log for Wifi Flip Clock/Youtube Counter

I see lots of electromechanical 7 segment flip clocks and such but no easy to use universal controller modules so this is my take on it

sjm4306sjm4306 12/17/2018 at 16:280 Comments

A quick video update on the first prototype boards I received from JLCPCB. In a nutshell I made a critically stupid design error in the way I had planned to drive these displays which means that I cannot independently drive segments in this revision. For this to work properly I would really need tristate drivers to ensure there are no unintended current paths for the disabled display's segments. I also overlooked a subtle gotcha in the datasheet for the motor driver chips I use where both outputs can never be high simultaneously (which is an issue when trying to reset segments). Additionally I've noticed these motor driver chips are pretty slow (on/off delay in the order of tens/hundreds of ms), but that shouldn't be much of an issue in a mechanical system like this. Oh well, I'll take this as a learning experience and start designing v2.0 of the board. Hopefully I'll have good news in the form of an update once I've ordered and assembled v2.0.